Report of the Court-appointed experts

MARITIME DELIMITATION IN THE CARIBBEAN SEA AND THE PACIFIC OCEAN
(COSTA RICA V. NICARAGUA)
EXPERT OPINION
Professor Eric Fouache
Professor Francisco Gutiérrez
30 April 2017

TABLE OF CONTENTS
Paragraphs
Introduction .................................................................................................................................. 1-6
I. Background information ..................................................................................................... 7-91
(1) Site visits .......................................................................................................................... 8-83
(a) First site visit .......................................................................................................... 11-45
(b) Second site visit ...................................................................................................... 46-83
(2) Documents communicated to the authors of the present Report ............................. 84-91
(a) Information transmitted by the Registry of the Court upon appointment .................... 84
(b) Additional information requested from the Parties ................................................ 85-86
(c) Information collected during the site visits ............................................................ 87-90
(d) Subsequent information transmitted by the Registry of the Court .............................. 91
II. Geographical and geomorphological setting ................................................................. 92-110
(1) General geographical features of the area ................................................................. 92-96
(2) Geomorphological-geographical units...................................................................... 97-110
(a) Los Portillos/Harbor Head Lagoon .............................................................................. 98
(b) Spit-barrier of Los Portillos/Harbor Head Lagoon ............................................... 99-102
(c) San Juan River ........................................................................................................... 103
(d) Isla Portillos ........................................................................................................ 104-106
(e) Spit of Isla Portillos ............................................................................................ 107-110
III. Answers to the questions of the Court ......................................................................... 111-195
(1) Answer to the first question .................................................................................... 116-118
(2) Answer to the second question ................................................................................ 119-184
(a) The starting-point of the land boundary identified by the first Alexander
Award ....................................................................................................................... 120-128
(b) Geographical co-ordinates of the land point which most closely
approximates to that identified by the first Alexander Award as the startingpoint
of the land boundary ....................................................................................... 129-184
(i) First option ....................................................................................................... 130-131
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(ii) Second option .................................................................................................. 132-184
a. Works of the Demarcation Commissions and General Alexander
(1897-1899) ................................................................................................... 135-146
b. Works of the Sub-Commission on Limits and Cartography
established by Costa Rica and Nicaragua (2002-2005) ................................. 147-158
c. First investigation phase ............................................................................. 159-171
d. Second investigation phase ........................................................................ 172-184
i. Location of the center of Plaza Victoria ................................................ 173-180
ii. Location of the Initial Marker (Mojón Inicial) ..................................... 181-183
iii. Land point which most closely approximates the Initial Marker ............... 184
(3) Answer to the third question ................................................................................... 185-190
(4) Answer to the fourth question ................................................................................. 191-195
*
Pages
References ...................................................................................................................................... 78
List of figures ............................................................................................................................. 79-87
List of tables ................................................................................................................................... 88
INTRODUCTION
1. On 25 February 2014, the Republic of Costa Rica (hereinafter “Costa Rica”) filed an
Application with the International Court of Justice (hereinafter “the Court”) against the Republic of
Nicaragua (hereinafter “Nicaragua”), requesting the Court
“to determine the complete course of a single maritime boundary between all the maritime areas
appertaining, respectively, to Costa Rica and to Nicaragua in the Caribbean Sea and in the Pacific
Ocean, on the basis of international law”.
2. Costa Rica “further request[ed] the Court to determine the precise geographical co-ordinates
of the single maritime boundaries in the Caribbean Sea and in the Pacific Ocean”.
3. In the Memorial, Costa Rica claims that the starting-point of the maritime delimitation
between the Parties on the Caribbean side is “on the right bank of the San Juan River at its mouth”
(para. 4.13). In the Counter-Memorial, Nicaragua contends that the starting-point is situated at the
extremity of Punta de Castilla, near the north-eastern corner of Harbor Head Lagoon (para. 3.48),
3.59 km east of that suggested by Costa Rica.
4. The Court, considering that there were certain factual matters relating to the state of the
coast between the point suggested by Costa Rica and the point suggested by Nicaragua in their
pleadings as the starting-point of the maritime boundary in the Caribbean Sea, which might be
relevant for the purpose of settling the dispute submitted to it, and that, with regard to such matters, it
would benefit from an expert opinion, decided, in an Order dated 31 May 2016, that “[a]n expert
opinion shall be obtained, which will be entrusted to two independent experts appointed by Order of
the President of the Court after hearing the Parties”.
5. In its Order of 31 May 2016, the Court also decided that:
“(2) The experts referred … above shall visit the site. They shall advise the Court regarding the
state of the coast between the point suggested by Costa Rica and the point suggested by Nicaragua in
their pleadings as the starting-point of the maritime boundary in the Caribbean Sea, and in particular
answer the following questions:
(a) What are the geographical co-ordinates of the point at which the right bank of the San Juan
River meets the sea at the low-water line?
(b) What are the geographical co-ordinates of the land point which most closely approximates to
that identified by the first Alexander Award as the starting-point of the land boundary?
(c) Is there a bank of sand or any maritime feature between the points referred to in subparagraphs
(a) and (b) above? If so, what are their physical characteristics? In particular, are these features, or
some of them, permanently above water, even at high tide? Is Los Portillos/Harbor Head Lagoon
separated from the sea?
(d) To what extent is it possible, or probable, that the area concerned will undergo major physical
changes in the short and long term?”
6. The authors of the present Report were appointed by an Order of the President of the Court
dated 16 June 2016.
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I. BACKGROUND INFORMATION
7. In order to answer the questions put by the Court, we conducted two site visits (explained in
subsequent section (1) below) and examined a number of documents communicated by the Parties
(listed below in subsequent section (2)). These elements will be summarily presented in this section
of the Report.
(1) Site visits
8. Having been requested by the Court to “visit the site” (see Order of 31 May 2016,
para. 10(2)), we conducted two visits to the site from 5 to 9 December 2016 (hereinafter “first site
visit”) and from 13 to 17 March 2017 (hereinafter “second site visit”), which allowed us to examine
the area under markedly different conditions. December and March are characterised by high and
low average monthly rainfall in the area, respectively.
9. The first site visit was carried out soon after Hurricane Otto had made landfall in the San
Juan de Nicaragua area on 24 November 2016. Otto was an exceptional event that caused significant
geomorphic and hydrological changes in the area under scrutiny (i.e., coastal erosion, opening of a
channel in the beach, high-water levels in lagoons, high flow in the San Juan River). This was the
southernmost hurricane on record to hit Central America and the first directly impacting on Costa
Rica (see more information on Hurricane Otto below, para. 96).
10. The second site visit was carried out in March, which is the month with the lowest average
rainfall in the area. Moreover, March also falls within a period characterised by low average
discharge values in the lower course of the San Juan River according to the supplementary data
submitted by Costa Rica on 20 October 2016 (discharge data from Delta gauging station).
(a) First site visit
11. A first site visit was conducted from 5 to 9 December 2016, less than two weeks after
Hurricane Otto impacted on the area. This visit allowed us to examine the geomorphic and
hydrological effects caused by that high magnitude and low frequency meteorological-hydrological
event along the coast. The main activities carried out during each of those days are indicated below:
Monday 5 December 2016 (Day 1):
12. The delegation left San José at 7:15 a.m., flying in a Costa Rican plane to the small airport
at Barra del Colorado, where we travelled by Costa Rican boat up the Río Colorado to Delta, crossed
into Nicaraguan territory, and proceeded by Nicaraguan boat down the lower San Juan River to the
Río Indio Lodge (Fig. 1).
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Figure 1. Annotated satellite image from December 2011 (U.S. Geological Survey)
showing the location of San Juan del Norte village, Río Indio Lodge, the airport of
San Juan del Norte built where Greytown used to be located, the San Juan River and
its mouth (its position is highly variable), Isla Portillos, and the Los Portillos/Harbor
Head Lagoon.
13. After a meeting to review security and medical procedures and discuss logistics, the
delegation left promptly for the field. We decided to concentrate our efforts initially on taking coordinates
of certain points of interest and assessing the general state of the coast and its surroundings.
14. Arriving at the mouth of the San Juan River (see Figure 1 above) in two Nicaraguan
military boats, GPS co-ordinates were taken at the end of the sand spit at the north-western part of
Isla Portillos and at the limit of the vegetation (in all cases where co-ordinates were taken, this was
done in parallel by the topographical teams of both Parties, as illustrated in several figures below).
15. We then decided to conduct a reconnaissance of the coastal stretch between the mouth of
the San Juan River and the eastern edge of Los Portillos/Harbor Head Lagoon. We therefore walked
from the river mouth to the lagoon. Before we arrived at the western edge of the lagoon, it was
necessary to cross a channel where water was draining from the lagoon to the sea (Fig. 2).
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Figure 2. Drainage channel encountered during the first site visit, in which water
was draining from the Los Portillos/Harbor Head Lagoon to the sea.
16. We then continued walking across the sand barrier between the lagoon and the Caribbean Sea.
Arriving on the other (eastern) side of Los Portillos/Harbor Head Lagoon, we took note of the
marker known as “A2” protruding from the water in the eastern corner of the lagoon (Fig. 3).
Figure 3. Image taken on the eastern corner of Los Portillos/Harbor Head Lagoon,
showing the marker known as “A2”.
17. We then returned to the mouth of the San Juan River by foot, where we boarded
Nicaraguan military vessels for the short trip through a series of caños to the lodge.
18. In the evening, a brief meeting was held during which we were able to meet the pilot of the
Nicaraguan drone (which would take pictures and videos of the coast the following day) and define
the flight path that the drone would take.
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Tuesday 6 December 2016 (Day 2):
19. Having arrived by boat at the mouth of the San Juan River, the delegation went on foot to
Los Portillos/Harbor Head Lagoon. On the way there, both topographical teams took GPS coordinates
at the channel through which the water from the lagoon was draining to the sea, close to the
western edge of the lagoon.
20. The delegation then returned by foot to the mouth of the San Juan to take GPS coordinates,
at the end of the sand spit at the north-western part of Isla Portillos. The co-ordinates were
taken at the low tide occurring at 11:26 a.m.
21. Meanwhile, the Nicaraguan drone operator conducted an overflight of the area to take
pictures and videos of the coast.
22. We returned to the lodge for lunch, after which we travelled by boat to the site of old
Greytown, located in the area of the landing strip of San Juan del Norte (see Figure 1 above). We
wanted to determine whether it was still possible to locate the center of a square (Plaza Victoria) that
was used, in 1898, as a reference point by the Demarcation Commissions established by Costa Rica
and Nicaragua1.
23. Docking at a Nicaraguan military camp, we crossed the landing strip, on the other side of
which (southern side) were situated several cemeteries (e.g., British, Catholic, Masonic) in a line (see
Figure 9 below).
24. We continued in an easterly direction along a path parallel to the landing strip on its
southern side. To the east of the cemeteries and south of the path, towards the eastern end of the
landing strip, we reached a site where Nicaragua claimed it was possible to view the remains of steps
which it considered were once part of the church overlooking Plaza Victoria. However, the steps in
question ascended to the south, whereas the church in question would have faced south and its steps
would have ascended to the north (Fig. 4). Moreover, according to old maps, as explained below,
Plaza Victoria should be located north of the path.
1 In Proceedings X of the Costa Rica-Nicaragua Demarcation Commissions (1898), the co-ordinates of
the Mojón inicial (which had been placed near Punta de Castilla) were given using as the origin a monument
placed in the center of Plaza Victoria, in front of a church (see Ann. 5 of Nicaragua’s Counter-Memorial).
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Figure 4. Steps presented by Nicaragua as possibly being those of the church that
would have been built on Plaza Victoria. Arrows indicate the orientation of the
stairs, ascending to the south (co-ordinates measured with a hand-held GPS: 17P
0204495E, 1208408N).
25. Returning to the lodge, the focus shifted to a marker found by both Parties in 2003 on the
beach near Los Portillos/Harbor Head Lagoon, which they saw on 21 February 2003, and for which
they measured the co-ordinates on 25 November 2003, during the field work of their Sub-
Commission on Limits and Cartography (see, for further details on this question, paras. 151-156
below). It was assumed that this marker could be one of the markers built in the late 1890s by the
Demarcation Commissions, and more precisely either marker Am or marker A1 depicted on the
sketch-map included in Proceedings XX of the Costa Rica-Nicaragua Demarcation Commissions
(1897-1900) (reproduced at Ann. 9 of Nicaragua’s Counter-Memorial) (see Figure 5 below). This
sketch-map will be discussed in further detail below (see paras. 135-146 below), but suffice it to say
for the moment that markers Am and A1 were auxiliary markers placed by the Demarcation
Commissions at the end of the 19th century, to ensure that the location of Punta de Castilla could be
always precisely determined.
- 7 -
Figure 5. Sketch-map included in Proceedings XX of the Costa Rica-Nicaragua
Demarcation Commissions (1897-1900), showing the location of Punta de Castilla
and auxiliary markers Am and A1, as well as their relative positions indicated by
distances and azimuths.
26. We agreed to look for this marker the following day, using the average of the co-ordinates
taken by the Parties in 2003 as a point of departure.
Wednesday 7 December 2016 (Day 3):
27. After being delayed by a heavy downpour, the delegation arrived at Los Portillos/Harbor
Head Lagoon at 9:40 a.m. to begin searching for the marker found on 21 February 2003 and for
which the Parties had measured the co-ordinates on 25 November 2003 with hand-held GPS devices.
28. Noting that the average of the co-ordinates taken in 2003 currently correspond to a point
situated in the sea, we operated on the hypothesis that the marker previously found was Am (if it were
to be A1, both points would be in the sea). We therefore used the triangulation values between
markers Am and A1 indicated in the sketch-map included in Proceedings XX of the Costa Rica-
Nicaragua Demarcation Commissions (1897-1900) (Fig. 5) to find the approximate location where
A1 could be buried on the beach. Then, we marked off a semi-circular research area of 15 m radius
(estimated error margin of the hand-held GPS device) for potential exploration around this point on
the beach side (Fig. 6). The remaining semi-circular area was located in the sea.
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Figure 6. Exploration area around a point established assuming that the average of
the co-ordinates measured on 25 November 2003 correspond to the location of
auxiliary marker Am and using the triangulation values indicated in the sketch-map
included in Proceedings XX of the Costa Rica-Nicaragua Demarcation
Commissions (1897-1900).
29. After discussions about the potential to bring a backhoe to the area, the delegation
eventually returned to the plan of searching for the marker with iron rods to probe the sand, and
manual digging when necessary.
30. Meanwhile, the Nicaraguan drone took videos and images along the coast.
31. We then returned to the site of the “A2” marker on the eastern edge of Los
Portillos/Harbor Head Lagoon. The Nicaraguan delegation took the position that it had been laid by
Alexander, while the Costa Rican delegation believed that it had not been constructed by Alexander
but rather built some time afterwards.
32. In the afternoon, we returned to the site of old Greytown. We requested that the two
topographical teams take the co-ordinates of the four corners of the landing strip to enable us to more
accurately georeference maps on which it appeared.
33. We then returned to the area containing what Nicaragua contended were the possible
remains of the church on Plaza Victoria. The area had been cleared of vegetation, but there was
nothing to change the previous day’s analysis: the stairs were facing the wrong direction for it to be
the church on Plaza Victoria. Furthermore, according to old maps, Plaza Victoria was located further
north.
34. Meanwhile, the Nicaraguan drone took videos at Isla Portillos, focusing on the channel in
which water was draining from the lagoon to the sea.
Thursday 8 December 2016 (Day 4):
35. Our departure from the lodge was once again delayed because of rain. We therefore
watched the videos taken by the drone on the previous day. We finally left at 8:30 a.m.
36. Having disembarked at the mouth of the San Juan River, we walked to the lagoon.
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37. On the eastern side of Los Portillos/Harbor Head Lagoon, we asked the topographers to
take the co-ordinates of the marker known as “A2”.
38. We then went towards the western end of the lagoon, near the search area defined on the
previous day.
39. Having asked the topographers to calculate more precisely the supposed position of the
marker A1 on the basis of the assumptions indicated above (this having been done the previous day
without all the proper equipment), we redefined the research area marking its center with a stick and
defining the perimeter of a semi-circular area 15 m radius on the beach. The other half of the new
research area was in the sea.
40. Together with members of each delegation, we formed a line and started probing the sand
with iron rods (Fig. 7). Unfortunately, the equipment was rather inadequate. The corrugated rods not
being easy to handle or sharp enough, they did not penetrate the ground more than 50 cm. Some
workers helped the search with shovels.
Figure 7. Row of delegates probing the sand with iron rods.
41. We found nothing and decided to go back to the lodge.
42. After a short break, we went by boat to the new town of San Juan del Norte in order to
visit the museum, which might have contained maps of old Greytown (Fig. 8).
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Figure 8. Museum of San Juan del Norte.
43. We would have liked to find maps enabling us to precisely locate Plaza Victoria. For that
purpose, a map showing both the cemeteries and Plaza Victoria would have been very useful. There
was, however, no such map in the museum.
44. In the evening, we held a final meeting with the representatives of the Parties, during
which the delegations agreed to transmit to the Court, by Wednesday 21 December 2016, at the
latest, the final co-ordinates (in WGS-84) taken by their respective topographical teams for the points
listed in Table 1 below (p. 40). We also asked the Parties if they could make known to the Court
their position on whether the marker found in 2003 was either A1 or Am, as identified in Proceedings
XX of the Demarcation Commissions (19 August 1899), and whether we could use the average coordinates
(namely 10° 56' 03'' N, 83° 40' 22.5'' W) recorded for this marker in 2003. Finally, we
asked the Parties if they could provide the co-ordinates of another marker (which Nicaragua had
stated it had seen on 26 November 2003 and which it said was currently submerged near the
north-western corner of the lagoon), and make known what they thought this other marker stood for.
This marker was presented as having been found “inclined and submerged” in the lagoon “by
approximately 98 mts to the south of the first marker found on the coast on Tuesday 24 [sic, should
be 25] November [2003]” (Minute of the Fourth Technical Meeting of the Sub-Commission on Limits
and Cartography, 24-27 November 2003, Counter-Memorial of Nicaragua, Ann. 15).
Friday 9 December 2016 (Day 5):
45. We departed by boat at 7:30 a.m. from the Río Indio Lodge and returned to the small
airport at Barra del Colorado, and from there to San José.
(b) Second site visit
46. A second site visit was conducted from 13 to 17 March 2017. This visit allowed us to
examine the area under much drier conditions than in the first site visit, with a much lower discharge
in the San Juan River and water level in the Los Portillos/Harbor Head Lagoon. The main activities
carried out during those days are indicated below:
Monday 13 March 2017 (Day 1):
47. The delegation left Managua at 8:15 a.m., flying in a Nicaraguan military helicopter to the
landing strip at San Juan del Norte (also known as Greytown).
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48. Immediately upon arrival, we started searching for the marker placed at the center of Plaza
Victoria, which we had calculated to be under or in the immediate vicinity of the landing strip. We
began by marking off the supposed center of Plaza Victoria, calculated through the geo-referencing
of old maps. An initial research zone 60 m by 25 m was defined in the landing strip, about one third
of the way from its eastern end.
49. The landing strip itself measured 25 m wide. Two cords were placed across it, marking off
the eastern and western extremities of the initial research area, and short colored (pink) ribbons were
tied on these cords every 155 cm, these representing the extremities of the Ground Penetrating Radar
(“GPR”) profiles (Fig. 10).
Figure 9. Area of the airport with locations of the corners of the cemeteries, the area of the airport
that was investigated and the church steps presented by Nicaragua.
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Figure 10. Placing of colored ribbons every 1.55 m on the cords
marking off the eastern and western extremities of the initial
research area, covering a 60 m long section of the landing strip.
50. The Nicaraguan GPR team was then dispatched to acquire 17 profiles along the 60 m long
section of landing strip with a spacing of 1.55 m to indicate the presence of any anomalies in the
ground below which could indicate the presence of the marker (Fig. 11). The metal detector
furnished by the Nicaraguan delegation was also employed to survey the initial research area, but its
use on the landing strip proved ineffective, detecting constant anomalies due to the presence of iron
reinforcement in the concrete (Fig. 12).
Figure 11. Acquisition by Nicaragua of GPR profiles using a GSSI system equipped
with a 200 MHz shielded antenna.
- 13 -
Figure 12. Surveying of the landing strip with the Nicaraguan metal detector
(VALLON model VMH3CS).
51. While this work was being carried out, we determined that the research area should be
expanded to encompass the adjacent zones on the northern and southern sides of the landing strip,
also 60 m in length. These zones around 25 m wide extended out from the landing strip to the fence
at the northern and southern perimeter of the airport (see Figure 9 above). We requested that these
areas be cleared of vegetation. Once the GPR concluded taking data of the initial research zone on
the landing strip, we expanded the zone by 60 m east and west on the landing strip (for a total of
180 m) and took additional GPR data in these areas (a total of 51 profiles 60 m long each). We
planned to expand the areas north and south of the landing strip in a similar manner once the
vegetation was cleared.
52. The GPR team having completed its work on the landing strip, we left the research area for
the Río Indio Lodge at 3 p.m.
53. That evening, a meeting was held during which the work-plan for the following day was
discussed.
Tuesday 14 March 2017 (Day 2):
54. The delegation left the lodge at 7:15 a.m. to measure the GPS co-ordinates of the mouth of
the San Juan River at low tide.
55. The mouth had changed since the first site visit. After calibrating the equipment and
bringing it along the sand spit to the mouth, both topographical teams took the GPS co-ordinates of
the mouth of the river at precisely 8:16 a.m. and 8:17 a.m., the timing of low tide according to their
respective tide tables (Fig. 13).
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Figure 13. Area of the river mouth with the points of interest measured during the two site visits
plotted on an aerial photograph dated 22 January 2016, when the sand spit was largely diminished.
56. Meanwhile, the Costa Rican drone operators arrived by quadracycle and conducted an
overflight of the coast of Isla Portillos, taking pictures and videos.
57. While this was being carried out, we left on foot for Los Portillos/Harbor Head Lagoon.
We conducted a reconnaissance of the coastal stretch between the mouth of the San Juan River and
the eastern edge of Los Portillos/Harbor Head Lagoon.
58. Based on co-ordinates provided by Nicaragua, we established a research area measuring
22 m by 27 m on the beach, near the northwestern corner of the lagoon, in order to look for the
marker found on 26 November 2003, submerged in Los Portillos/Harbor Head Lagoon, and which
Nicaragua said was “in shallow water and not difficult to locate” (letter dated 21 December 2016
from the Agent of Nicaragua to the Registrar of the Court). Cords were stretched at each end and
marked every 2 m with ribbon, after which the Costa Rican GPR team collected data of the entire
area (a total of 12 profiles 27 m long) in the same manner as that carried out by the Nicaraguan GPR
at the landing strip the previous day (Fig. 14).
- 15 -
Figure 14. Initial research area established on the western side of Los Portillos/Harbor
Head Lagoon using the co-ordinates given by Nicaragua for the marker found on
26 November 2003 (10º 56’ 2.3’’N, 83º 40’ 24.4’’W). The location of that point was
marked with a wooden stick (see arrow). The Nicaraguan operator of the metal
detector is standing next to the stick. In the foreground, the GSSI GPR system of
Costa Rica with a 400 MHz shielded antenna.
59. Meanwhile, the operator of the metal detector surveyed the area, finding several
anomalies. Following excavation, however, these proved to be only small cans or other metallic
debris. We requested to view the GPR profiles after a basic processing immediately in the field,
locating two possible anomalies. Following excavation, these proved to be false positives most
probably related to localized variations in the sandy sediments. We then began searching in the area
by piercing the sand with 2 m long iron rods supplied by the Parties, which reached full penetration
(Fig. 15). This intrusive and direct method, although tedious, was considered more reliable than the
GPR, which showed poor performance in the southern sector situated at a lower elevation, with a
shallower water table.
Figure 15. Piercing the sand with 2 m long iron rods.
- 16 -
60. It was also decided, following consultation with the Parties, to expand the research area
towards the southwest, slightly into the vegetation and closer to the channel-shaped north-western
edge of the lagoon. Piercing the sand with the 2 m rods proved effective albeit difficult, and it was
decided to return to the same area the following day and repeat this procedure more systematically,
piercing every corner of a large grid composed of 40 cm squares.
61. We left the research area at 3:30 p.m., returning on foot to the mouth of the San Juan and
then going by boat back to the landing strip, where we found part of the expanded research zone
cleared of vegetation, while another part still needed clearing.
62. Returning to the lodge at 5 p.m., we held a meeting with the Parties in the evening at
which Nicaragua provided the GPR data from the airport, from which it was inferred that the landing
strip and its foundation probably extended to a depth of 1.5 m. The representatives of Costa Rica
gave us the pictures and videos taken by their drone.
Wednesday 15 March 2017 (Day 3):
63. We departed from the hotel at 7:15 a.m., in two boats, to the mouth of the San Juan River,
where we immediately walked towards Los Portillos/Harbor Head Lagoon, to take the GPS coordinates
of the eastern edge of the sand barrier of the lagoon at low tide (which was at 8:57 a.m.).
64. On the way, we stopped near the western edge of the lagoon to define a research area to be
examined systematically with iron rods. One section (defined the previous day in order to locate the
marker that Nicaragua had found on 26 November 2003) of approximately 27 m by 15 m was
marked off to be examined with the 2 m iron rods, piercing every 40 cm. Another area, closer to the
sea, in which the ground surface was higher, of approximately 27 m by 7 m, was marked off to be
first cleared of 1 m of sand with shovels and then examined in the same manner as the first one, with
the iron rods. The teams began this process, with almost everyone taking part and working together.
Sticks were placed in the holes after the rod had pierced 2 m without encountering an obstacle
(Fig. 16).
Figure 16. Lowering the higher portion of the beach with shovels and piercing
systematically the sandy ground with 2 m long iron rods. The sticks mark the
investigated points, forming a grid with a spacing of around 0.4 m.
- 17 -
65. While this work continued, we went with the topographers to the eastern edge of the
lagoon. We first took the GPS co-ordinates of the north-eastern corner of the water body of the
lagoon. At low tide time (8:57 a.m.) we took the co-ordinates of the eastern edge of the barrier that
encloses the lagoon at the beach.
66. When we returned to the other side of the lagoon, we asked the topographers to take the
co-ordinates of the point marking the western edge of the water body of the lagoon.
67. During all this time, the systematic piercing of the research area continued.
68. Given the work to be done at the airport, we considered it best to divide into two groups.
One group, including members of both Parties’ delegations and one Registry staff member, expanded
the search area on Isla Portillos, while we left with other members of the Parties’ delegations and
another Registry staff member to pursue the work at the airport. Before leaving, we redefined an
expanded research area, towards the mangrove forest in a marshy area covered by discontinuous
vegetation.
69. At the airport, the area we had defined north of the landing strip (approximately 180 m x
25 m) had been completely cleared of vegetation by the Nicaraguan workers. The equivalent area
south of the landing strip had only been partially cleared.
70. The Nicaraguan operator of the metal detector had identified various anomalies in the area
north of the landing strip and marked them with sticks. They were checked systematically, with
diggers making a hole until the metal object in question was found.
71. The Nicaraguan GPR team began surveying the area north of the landing strip. After a
short time, however, they announced that the two batteries of the GPR had died. The GPR operators
returned to the hotel by boat to charge them again for about 2 hours, at which point they began their
examination anew. After a short while, however, the batteries died again. It was decided that the only
option was to try to cover the entire area the following day, after the batteries had time to charge
again through the night.
72. During this entire time, teams continued to dig for anomalies discovered by the metal
detector operator, first on the northern side of the landing strip and eventually on the southern side as
well. Work continued until approximately 5 p.m.
Thursday 16 March 2017 (Day 4):
73. Given the work to be done during this last day, we considered it was best to divide into
two groups. We both went, with members of each delegation and a Registry Staff Member, to the
airport, while another group, with members of each delegation and a Registry Staff Member,
returned to the research area near Los Portillos/Harbor Head Lagoon.
74. At the airport, one of us went directly to the landing strip to continue to survey with the
GPR and dig up anomalies found by the metal detector. Meanwhile, the other went into the forest
abutting the airport (to the west) with a guide and the topographical teams to examine the area where
the old railroad used to run. We wanted to take co-ordinates to enable us to georeference with more
precision old maps showing these train tracks.
75. Unfortunately, because of the damage caused by Hurricane Otto and especially the huge
number of fallen trees, it was not possible to reach the old railway. We therefore decided to take the
co-ordinates of the external angles of a geographical feature which we had identified on the old maps
and was still visible today. This feature is a rectangle dug on the southern bank of what seems to be
an artificial channel (see Map of Greytown Harbor (1899), Documents submitted by Nicaragua on
20 October 2016 (Fig. 17)).
- 18 -
Figure 17. Map of Greytown Harbor (1899). The enlargement shows the
rectangular excavation at which co-ordinates were taken. The black lines along the
shore depict the path of the old railway.
76. As the batteries of the GPR died, once again, after a short while, we decided to join the
second group at Isla Portillos while the operators of the device went back to the hotel to charge them.
77. When we arrived near the lagoon, the search area had almost been fully explored. We
helped with the last parts and decided to end the operations. No marker was found.
78. We took a number of co-ordinates along the boundaries of the search area (Fig. 18).
- 19 -
Figure 18. Area of the lagoon with the points of interest measured during the two site visits
projected on a satellite image of 22 January 2016.
79. Thereafter, we went back to the hotel and checked the GPR profiles taken in the morning.
We noted all the anomalies we saw, even if minor or ambiguous.
80. The GPR having been recharged, we went back to the airport at 3 p.m.. There, we
continued collecting profiles in the search area, reviewed on the spot the profiles taken during the
afternoon and checked all the anomalies we had noticed.
81. As nightfall was approaching, we had to stop our investigations. No marker was found.
- 20 -
82. We held a final meeting with the representatives of the Parties, during which the
delegations agreed to transmit to the Court, by Friday 24 March 2017, at the latest, the final coordinates
(in UTM and sexagesimal format) taken by their respective topographical teams for the
points mentioned in Table 1 below (p. 40) (see also Figures 9, 13, 18). The delegations also agreed
to provide the processed profiles taken by the GPR devices of their respective teams, indicating the
system and the software used, as well as the methodology applied.
Friday 17 March 2017 (Day 5):
83. We departed by boat at 8 a.m. from the Río Indio Lodge and returned to Managua by
military helicopter.
(2) Documents communicated to the authors of the present Report
(a) Information transmitted by the Registry of the Court upon appointment
84. Upon our appointment, the Registry communicated to us the Application submitted by
Costa Rica instituting proceedings against Nicaragua in the case concerning Maritime Delimitation
in the Caribbean Sea and the Pacific Ocean (Costa Rica v. Nicaragua) (filed in the Registry of the
Court on 25 February 2014), as well as the Memorial of Costa Rica (two volumes, dated 3 February
2015) and the Counter-Memorial of Nicaragua (one volume, dated 8 December 2015).
(b) Additional information requested from the Parties
85. Before conducting the first site visit, the Parties have been requested to communicate to us
various documents (aerial photographs, maps, satellite images, geodetic data, tide records, discharge
time-series). All these elements were submitted on 20 October 2016.
86. Before the second site visit, each of the Parties communicated to the Court the tide tables
for the area of San Juan de Nicaragua, for the month of March 2017.
(c) Information collected during the site visits
(i) First site visit
87. During the first site visit, Nicaragua provided the authors of the present Report with videos
and photographs taken by a drone on 6 and 7 December 2016.
88. Afterwards, by letters dated 21 December 2016, the Parties provided the geographical coordinates
measured during the first site visit2. They also communicated additional information
requested by the authors of the present Report, namely co-ordinates and images of the marker found
on 21 February 2003 and of the additional marker, found on 26 November 2003, submerged in the
northwestern sector of the Los Portillos/Harbor Head Lagoon. Each Party also recorded the position
of its Government on whether the first of these markers was either Am or A1.
(ii) Second site visit
89. During the second site visit, Costa Rica provided the authors of the present Report with
videos and photographs taken by a drone on 14 March 2017.
2 By a letter dated 24 January 2017, Nicaragua provided revised co-ordinates for two points.
- 21 -
90. Under cover of a letter dated 24 March 2017, Costa Rica provided the final co-ordinates
taken by its topographical team during the second site visit3, as well as a report by Costa Rica’s
National Museum explaining the methodology and results of the survey carried out with the Costa
Rican GPR. Under cover of a letter also dated 24 March 2017, Nicaragua provided the final coordinates
taken by its topographical team during the second site visit, as well as an INETER report
explaining the methodology and results of the survey carried out with the Nicaraguan GPR.
(d) Subsequent information transmitted by the Registry of the Court
91. On 18 April 2017, the Registry communicated to us copies of the Parties’ written
pleadings (Memorial of Costa Rica and Counter-Memorial of Nicaragua) in the case concerning
Land Boundary in the Northern Part of Isla Portillos (Costa Rica v. Nicaragua), which had been
joined with the case concerning Maritime Delimitation in the Caribbean Sea and the Pacific Ocean
(Costa Rica v. Nicaragua) by an Order of the Court dated 2 February 2017.
*
3 By a letter dated 30 March 2017, Costa Rica provided revised co-ordinates.
- 22 -
II. GEOGRAPHICAL AND GEOMORPHOLOGICAL SETTING
(1) General geographical features of the area
92. The starting-points of the maritime boundary between Nicaragua and Costa Rica in the
Caribbean coast proposed by both Parties are located in a coastal stretch associated with Los
Portillos/Harbor Head Lagoon and the mouth of the San Juan River. This river, around 200 km long
and with a catchment area of approximately 38,500 km2, starts from Lake Nicaragua (or Cocibolca
Lake) in Nicaragua. At around 19 km west of the Caribbean coast near Delta, the San Juan River
splits into two main channels (Fig. 19). The southern one is called the Colorado River, which shows
a major anabranch. Nowadays it carries most of the discharge of the fluvial system and has formed a
wave-dominated cuspate delta in the Barra del Colorado area. Deltas in coasts with strong wave
action tend to have a cuspate morphology, with a high width/length ratio, whereas deltas in which
fluvial sediment supply overwhelms the erosional effect of waves tend to project into the sea
showing a lower width/length ratio and a lobate or triangular geometry. The northern channel,
despite its current lower flow, is designated as the San Juan River. This branch has an E-W
orientation in its initial stretch and at around 9 km west of the coast turns into a general N-S
direction.
Figure 19. Annotated satellite image (Landsat, December
2016) showing the main geographical-geomorphic features of
the lower reaches of the San Juan fluvial system associated
with the Caribbean coast.
93. Reports from 1848 indicate that around 90% of the discharge of the San Juan River used to
flow into the San Juan del Norte Bay and the remaining 10% into the Colorado River (Rabella,
2004). Floods occurred in 1861 causing a significant increase in the discharge of the Colorado River
at the expense of the Lower San Juan River (González, 1994). In 1865, Captain G.C. West from the
Department of Coastal Studies of the USA reported that 92% of the discharge of the San Juan River
flowed into the Caribbean Sea through the Colorado River (Rabella, 2004). The sharp reduction that
- 23 -
the Lower San Juan River experienced in 1861 is very likely the main cause for the rapid retreat that
has affected the coast associated with Los Portillos/Harbor Head Lagoon in historical times. The
sediment that nourishes beaches is mainly related to the sedimentary input of fluvial systems, which
is redistributed along the coast by long-shore currents. It seems that since the 1861 flood, the
diminished sediment flux that the Lower San Juan supplies to the coast is insufficient to
counterbalance the effect of erosional coastal processes.
94. The San Juan and the Colorado in their lower reaches flow across a broad coastal plain
with relatively flat topography locally interrupted by hills corresponding to inliers of Plio-Quaternary
volcanic rocks (Bergoeing, 2014). The coastal fringe is characterised by the presence of numerous
narrow coast-parallel beach ridges (relict beach accumulations) and lagoons related to long-term
progradation in a wave-dominated coastal environment (Parkinson et al., 1998; Scheffers and
Browne, 2010; Bergoeing, 2014). According to the numerical radiocarbon ages obtained by
Nieuwenhuyse and Kroonenberg (1994) in the Tortuguero area, Costa Rica, the sandy beach-ridge
plain has developed over the last 4-5 millennia. The San Juan and the Colorado rivers show distinct
coast-parallel deflections at the mouth sector related to the growth of spits generated by strong
northerly littoral drift (Parkinson et al., 1998) (Fig. 19). The tides, with a range of around 0.2-0.5 m
(micro-tidal regime) according to the tide data (2009-2016) supplied by Costa Rica, have a limited
geomorphic impact on the coast (Nieuwenhuyse and Kroonenberg, 1994; Bergoeing, 2014).
95. The climate has exceptionally wet tropical conditions, with an annual average precipitation
in San Juan del Norte, Nicaragua, of 5,670 mm and a mean temperature of 26.2 ºC (data from
CLIMATE-DATA.ORG).
96. The impact of hurricanes in the analysed sector is relatively small compared with other
sectors of the Caribbean coast located further north. Alvarado and Alfaro (2003), in their analysis of
the frequency of tropical cyclones that affected Costa Rica in the 20th century indicate the following
features: (1) the country was not affected directly by any cyclone in the 20th century, and the
probability of direct impact is equal or lower than 5%; (2) the five most intense hurricanes that
indirectly affected Costa Rica in the 20th century were Janet (September 1955), Camille (August
1969), Allen (July-August 1980), Gilbert (September, 1988), and Mitch (October, 1998); (3) the
cyclones with trajectories closest to Costa Rica (Limón taken as reference) were Irene (September
1971, 145 km), Bret (August 1993, 125 km; 40 km north of the border with Nicaragua), and Gert
(September 1993, 140 km); (4) the most damaging cyclones in terms of economic losses and
fatalities were Kattie (October, 1955), Joan (October, 1988), and Cesar (July 1996). Nonetheless,
Hurricane Otto directly impacted Costa Rica and Nicaragua in November 2016. This hurricane made
landfall about 10 nautical miles (18.5 km) northwest of the Nicaragua/Costa Rica border at around
1730 UTC on November 24 with an estimated intensity of 100 kt (185 km/h; category 3 on the
Saffir-Simpson Hurricane Wind Scale), causing significant economic and societal losses (National
Hurricane Center, 2017) (Fig. 20) and substantial geomorphic changes in the coastal fringe (e.g.,
opening of channels, erosion in sand spits and beaches). This was an unusual hurricane due to the
following features (National Hurricane Center, 2017):
(1) It is the southernmost hurricane on record to hit Central America and the first directly
impacting on Costa Rica;
(2) The hurricane occurred at very late stage of the Atlantic hurricane season. Otto marked 2016
as the second longest-duration Atlantic hurricane season, with tropical storms from January
to November;
(3) It traversed Central America from the Atlantic to the eastern North Pacific basin maintaining
tropical cyclone status.
- 24 -
Figure 20. Effects of Hurricane Otto in the cemetery of Greytown. Image taken
during the first site visit on 6 December 2016 (twelve days after Otto made
landfall in the area).
(2) Geomorphological-geographical units
97. The area under scrutiny comprises the following geomorphological-geographical units that
are relevant to the case (Fig. 21):
Figure 21. Sketch illustrating the geomorphological-geographical units of the
analysed area relevant to the case.
(a) Los Portillos/Harbor Head Lagoon
98. This lagoon is located next to the coastline and is enclosed or semi-enclosed by a sand
spit-barrier. The erosional retreat of the coast in historical times has considerably reduced the extent
of this water body (Fig. 22). Punta de Castilla was located on the northeastern corner of this lagoon
in the 1897 Award: “the headland [in 1897], or the northwestern extremity of what seems to be the
solid land, on the east side of Harbor Head Lagoon” (Fig. 23).
- 25 -
Figure 22. Cartographic overlay of the coastline as represented in a historical map produced by George
Peacock in 1832 and updated in 1840, on a satellite image taken on 5 October 2013. Note the retreat of
the coastline and the reduction of the extent of Los Portillos/Harbor Head Lagoon (Figure 2 of the
Statement from March 2015 prepared by Prof. Colin Thorne in relation with the case concerning
Certain activities carried out by Nicaragua in the border area (Costa Rica v. Nicaragua)).
Figure 23. View of the relatively firm and stable land covered by coconut trees that
forms the eastern edge of Los Portillos/Harbor Head Lagoon. In the background
and to the left, the spit-barrier of Los Portillos/Harbor Head Lagoon is visible.
Image taken during the second site visit on 15 March 2017.
(b) Spit-barrier of Harbor Head/Los Portillos Lagoon
99. This is a ribbon-shaped and coast-parallel beach accumulation essentially devoid of
vegetation that encloses or semi-encloses Harbor Head/Los Portillos Lagoon (Fig. 21). This barrier
- 26 -
mainly consists of loose sand and is attached to more solid land on the eastern corner of the lagoon
(Figs. 23, 24, 25).
100. The 1897 Award located Punta de Castilla on solid land at the base of the spit as it
existed in 1897. Topographic maps produced by Costa Rica and Nicaragua show that in the recent
past there used to be a channel-like water gap between the spit and firm land, and that the Los
Portillos/Harbor Head Lagoon was connected to the sea via the San Juan River (Fig. 26). During our
first site visit carried out in December 2016, when the water level of the lagoon was exceptionally
high, the sand spit-barrier extended from measured point Ple (Fig. 27, see co-ordinates in Table 1) to
point Plw. Point Plw was measured on the western extremity of the lagoon as defined by a highwater
mark consisting of stranded debris (highest stage reached by the lagoon water after Hurricane
Otto) (Fig. 28).
101. During this first visit the lagoon was draining towards the sea through a channel situated
next to point Pch, around 200 m to the northwest of point Plw, most probably breached by Hurricane
Otto (Figs. 29, 30, 31). In the second site visit, the eastern and western extremities of the water body
of the lagoon were measured at points Ple2 (Fig. 32) and Plew2 (Figs. 33, 34), respectively. The
intersection between the shoreline and the projection of the northeastern corner of the Los
Portillos/Harbor Head Lagoon perpendicular to the coast was measured in the second visit at low tide
(15 March 2017; 8:57 a.m.) at point Pleb (Fig. 35). In this second visit, the channel that was draining
the lagoon during the first visit was closed by a sandy beach deposit (Fig. 36).
102. The spit-barrier of the lagoon is a labile feature highly susceptible to coastal erosion and
the development of inlet channels. Photographs taken in June, July and August 2012 by Costa Rica
show a breach in the central sector of the spit-barrier (Fig. 37, provided by Costa Rica on 20 October
2016).
Figure 24. Sand spit-barrier between Los Portillos/Harbor Head Lagoon (left) and
the Caribbean Sea (right). View looking to the west. Image taken during the first
site visit on 6 December 2016.
- 27 -
Figure 25. Sand spit-barrier between the Caribbean Sea (left) and Los
Portillos/Harbor Head Lagoon (right). View looking to the east. Image taken
during the first site visit on 5 December 2016.
Figure 26. Portions of the 1970 and 1988 editions of the 1:50,000 scale topographic maps
of Punta de Castilla (sheet 3448 I) of the Instituto Geográfico Nacional de Costa Rica.
The maps reveal that there used to be in recent times a channel-like water gap connecting
the Los Portillos/Harbor Head Lagoon with the San Juan River. Note that at that time the
spit associated with the mouth of the San Juan River was attached to Punta de Castilla,
not to the western extremity of Isla Portillos (see Figure 3 for comparison).
- 28 -
Figure 27. Point Ple located at the base of the sand spit-barrier of the Los
Portillos/Harbor Head Lagoon. This point is located at the contact between the
relatively stable surface covered by tree vegetation on the eastern margin of the
lagoon, and the accumulation of loose sand that forms the spit-barrier. The GPS
receiver of Costa Rica is located at the base of a coconut tree. The flooded coconut
trees in the background reveal the high water level that reached the lagoon after
Hurricane Otto. Image taken during the first site visit on 6 December 2016.
Figure 28. Point Plw measured during the first site visit at the western extremity of
Los Portillos/Harbor Head lagoon. The point was located at a high-water mark
defined by stranded vegetation indicating the maximum level reached by the water
of the lagoon after Hurricane Otto. Image taken on 6 December 2016.
- 29 -
Figure 29. Channel breached in the beach of Isla Portillos, west of the spit-barrier
of Los Portillos/Harbor Head Lagoon. The water of the lagoon was flowing
towards the sea through this channel. The star indicates the location of point Pch.
Image captured from a video recorded by the Nicaraguan delegation during the
first site visit in December 2016.
Figure 30. Topographer of the Costa Rican delegation measuring the eastern bank
of the channel through which the lagoon was draining towards the sea (point Pch).
On the other side of the channel the tree vegetation is in direct contact with the sea
waves. Image taken during the first site visit on 6 December 2016.
- 30 -
Figure 31. Channel opened in the beach of Isla Portillos, close to the western
extremity of the Los Portillos/Harbor Head Lagoon. The water of the lagoon was
flowing into the sea. Flow direction is towards the camera. Image taken during the
first site visit on 8 December 2016.
Figure 32. Image of Point Ple2, which represents the easternmost edge of the water
body of Los Portillos/Harbor Head Lagoon on its northeast corner during the
second site visit. The point was marked with a wooden stick, being measured by a
topographer from Nicaragua (right). The monument to the right corresponds to a
marker whose designation (Δ and a reversed s as subscript, referred to by the
Parties as the “A2” Marker) has not been identified in the Proceedings of the Costa
Rica-Nicaragua Demarcation Commissions of the end of the 19th century. Image
taken during the second site visit on 15 March 2017.
- 31 -
Figure 33. Point Plw2 (asterisk) measured during the second site visit at the western
extremity of the water body of Los Portillos/Harbor Head Lagoon and general view
of its sand barrier. Image captured by the drone of the Costa Rican delegation in
March 2017.
Figure 34. Topographer of Costa Rica (left) measuring the co-ordinates of the
western extremity of the water body of Los Portillos/Harbor Head Lagoon
(covered by floating debris) during the second site visit. Image taken on 15 March
2017.
- 32 -
Figure 35. Point Pleb (wooden stick) measured during the second site visit at low
tide (15 March 2017, at 8:57 a.m.). This point represents the intersection between
the shoreline and the projection of the northeastern corner of the Los
Portillos/Harbor Head Lagoon perpendicular to the coast.
Figure 36. Position of the channel opened by Hurricane Otto (arrow). The channel
was closed during the second site visit due to the recovery of the sandy beach.
Image captured by the drone of the Costa Rican delegation during the second site
visit in March 2017.
- 33 -
Figure 37. Oblique aerial photograph of the spit-barrier of Los Portillos/Harbor
Head Lagoon showing a temporary inlet channel. Image taken on
3 August 2012.
(c) San Juan River
103. This channel has a NNW-SSE straight orientation west of Los Portillos/Harbor Head and
turns into a general ENE-WSW trend in the mouth area, where it shows a sinuous course (Fig. 21).
On the right margin of the San Juan River there is a series of secondary minor channels (caños)
directed towards the NE that may function during high flow periods.
(d) Isla Portillos
104. In this Report, Isla Portillos is defined as a portion of land, mostly covered by dense tree
vegetation, framed by Los Portillos/Harbor Head Lagoon, the San Juan River and the Caribbean Sea,
excluding the highly variable sand spit that grows from its northwestern extremity (Fig. 21). Isla
Portillos is essentially an abandoned microdelta formed by the San Juan River when it used to flow
into a large bay through multiple distributary channels, as shown in historical maps (see for example
Figures 22 and 38).
105. During the first site visit, to the west of the channel opened by Hurricane Otto there was a
coastal section affected by active erosional retreat. In this section, between point Pch and a point
with co-ordinates 17P 0207176E 1210255N (measured with a hand-held GPS during the first site
visit; error margin of 3 m), the waves were impacting directly on the tree vegetation of Isla Portillos.
Some trees were located within the sea and others were being undermined by wave erosion (Fig. 39).
106. In the second site visit, the sandy beach had largely recovered, reaching in most of this
section a width of around 50 m (Fig. 40). Wave action during severe storms tends to erode beach
deposits and transport them offshore. Beaches recover by progressive sediment accumulation under
ordinary conditions. The remaining coastal sector of Isla Portillos showed a broad and continuous
sandy beach during both visits. Between the beach and the area covered by tree vegetation there is a
series of discontinuous coast-parallel lagoons (Figs. 41, 42). The elongated lagoons are essentially
remnants of the channel-like water gap that used to exist in recent times between Isla Portillos and
the spit of Los Portillos/Harbor Head Lagoon (Fig. 26). In the western sector of Isla Portillos, the
forested area is in direct contact with the sand beach and there are no lagoons with free-standing
water (Fig. 43).
- 34 -
Figure 38. Map of San Juan del Norte Bay produced by George
Peacock in 1832 and updated in 1840. The San Juan River used to
flow into an open lagoon through multiple distributary channels
forming a small delta, which nowadays roughly corresponds to Isla
Portillos, as defined in this Report.
Figure 39. Image of the coastal stretch of Isla Portillos affected by severe erosional
retreat. Here, the mangrove forest is in direct contact with the sea and affected by
wave action. Image taken during the first site visit on 5 December 2016.
- 35 -
Figure 40. Coastal stretch of Isla Portillos, which was affected by severe erosional
retreat during the first site visit. This image, taken during the second site visit,
illustrates the considerable recovery of the beach by sand accumulation related to
wave action under regular conditions.
Figure 41. Discontinuous and elongated lagoons between the beach and the
relatively stable area covered by dense vegetation of Isla Portillos. Image captured
from a video recorded by Nicaragua with a drone during the first site visit in
December 2016.
- 36 -
Figure 42. Oblique aerial view taken by the Costa Rican drone during the second
site visit in March 2017, showing the discontinuous lagoons between the beach and
the area covered by dense vegetation of Isla Portillos. Note that the lagoons were
much less extensive than during the first site visit (see figure 41 for comparison).
Figure 43. Western sector of the coast of Isla Portillos, close to the mouth of the
San Juan River, where the lagoons or coastal lakes terminate before the mouth of
the San Juan River. Image captured from a video recorded by Nicaragua with a
drone during the first site visit in December 2016.
(e) Spit of Isla Portillos
107. This is a narrow and coast-parallel spit at the mouth of the San Juan River that grows by
littoral drift from the northwest extremity of Isla Portillos. This ephemeral accumulation deflects the
final course of the San Juan River and displaces its mouth towards the west (Fig. 21). This sensitive
feature has experienced significant changes in the last few decades related to sedimentation and
erosion processes with the consequent alterations in the configuration and position of the San Juan
River mouth (Fig. 44).
- 37 -
108. Costa Rica in its pleadings proposes the base of this sand spit as the starting-point of the
maritime boundary: “at the base of the sand spit extending northwest from Isla Portillos, because no
reliable base points can be derived from this ephemeral low-lying feature”.
109. In the first site visit the base of the spit was located at point Pv on the western edge of the
tree vegetation growing on slightly higher ground, and where the loose sand deposit of the spit
started (Figs. 45, 46). No changes were observed in the second site visit at this spot. During the first
visit (December 2016) the spit was just around 210 m long at low tide, most probably due to
significant erosion caused by the Hurricane Otto in the previous month (Fig. 46).
110. In the second visit it was about 880 m long, indicating a rapid growth in length of ca.
670 m in about 3 months (Figs. 13, 47).
Figure 44. Sequence of maps illustrating the main changes in the coastline identified comparing
satellite images from different dates (January 1970, December 2011, June 2013, April 2014). The
satellite images were retrieved from the historical imagery of GoogleEarth. Note the substantial
modifications experienced by the spit of Isla Portillos at the mouth of the San Juan River (right bank).
- 38 -
Figure 45. The Nicaraguan delegation measuring the geographical co-ordinates at
the base of the sand spit of Isla Portillos (point Pv). Image taken during the first
site visit on 5 December 2016.
Figure 46. Image captured by the drone of the Nicaraguan delegation in December
2016, showing the spit of Isla Portillos and the mouth of the San Juan River on its
eastern bank. The spit was most probably diminished by erosion associated with
the Hurricane Otto (24 November 2016). The star indicates the location of
point Pv.
- 39 -
Figure 47. Spit of Isla Portillos and the mouth of the San Juan River on its eastern
bank (arrow) during the second site visit. The spit experienced a significant
westward growth by sand accretion between the first and the second visit (see
Figure 46 for comparison). Image captured by the drone of the Costa Rican
delegation in March 2017.
*
- 40 -
Table 1. Geographical co-ordinates measured by the topographical teams of Nicaragua and
Costa Rica during the site visits and used in this Report
(WGS 1984 coordinate system)
FIRST SITE VISIT
Code Name Nicaragua Costa Rica
Prm River mouth first 205021.82 E 1210725.30 N
205021.99 E 1210725.29 N
Prmb River mouth second 204965.88 E 1210750.48 N 204966.09 E 1210750.50 N
Pv Vegetation 205128.22 E 1210619.32 N 205128.41 E 1210619.28 N
Ple Lagoon east 208431.57 E 1209509.95 N 208431.78 E 1209510.01 N
Plw Lagoon west 207785.83 E 1209959.32 N 207786.05 E 1209959.36 N
Pch Channel 207625.75 E 1210079.78 N 207625.97 E 1210079.78 N
Pa2 Marker “A2” 208421.21 E 1209499.91 N 208421.59 E 1209499.94 N
SECOND SITE VISIT
Code Name Nicaragua Costa Rica
Prm2 River mouth
second visit
204365 E 1211067 N 204365.522 E 1211066.661N
Plw2 Lagoon west 2 207787 E 1209944 N 207786.928 E 1209944.489 N
Ple2 Lagoon east 2 208424 E 1209504 N 208424.307 E 1209503.772 N
Pleb Lagoon east
beach
208466 E 1209545 N 208466.029 E 1209545.191 N
Pp1 Probing 207762 E 1209980 N 207761.942 E 1209979.925 N
Pp2 Probing 207757 E 1209975 N 207756.618 E 1209974.599 N
Pp3 Probing 207763 E 1209969 N 207763.006 E 1209969.442 N
Pp4 Probing 207760 E 1209966 N 207760.412 E 1209966.129 N
Pp5 Probing 207762 E 1209965 N 207769.610 E 1209950.925 N
Pp6 Probing 207757 E 1209968 N 207778.587 E 1209947.785 N
Pp7 Probing 207770 E 1209951 N 207777.632 E 1209958.058 N
Pp8 Probing 207779 E 1209948 N 207787.449 E 1209968.646 N
Pp9 Probing 207781 E 1209949 N 207767.465 E 1209986.806 N
Pp10 Probing 207783 E 1209954 N
Pp11 Probing 207778 E 1209958 N
Pp12 Probing 207787 E 1209969 N
Pp13 Probing 207768 E 1209987 N
PairNE GPR airport 204562 E 1208499 N 204561.467 E 1208498.913 N
PairSE GPR airport 204553 E 1208420 N 204553.131 E 1208419.741 N
PairNW GPR airport 204382 E 1208512 N 204381.651 E 1208512.200 N
PairSW GPR airport 204374 E 1208433 N 204373.640 E 1208433.157 N
*
- 41 -
III. ANSWERS TO THE QUESTIONS OF THE COURT
111. Our mission was to “advise the Court regarding the state of the coast between the point
suggested by Costa Rica and the point suggested by Nicaragua in their pleadings as the starting-point
of the maritime boundary in the Caribbean Sea”, and in particular to answer four specific questions
(see paragraph 5).
112. It is recalled that, in the case concerning Maritime Delimitation in the Caribbean Sea and
the Pacific Ocean (Costa Rica v. Nicaragua), the Parties each submitted only one pleading (a
Memorial for Costa Rica and a Counter-Memorial for Nicaragua).
113. In its Memorial, Costa Rica claims that the starting-point of the maritime delimitation
between the Parties on the Caribbean side is
“on the right bank of the San Juan River at its mouth: the point at which the line
dividing the land territories of the two States intersects the coast. That point is located
at the north-western extremity of Costa Rica’s Isla Portillos, where Costa Rica’s land
territory and Nicaragua’s waters of the San Juan River meet the Caribbean Sea”
(Memorial of Costa Rica, para. 4.13).
Costa Rica places the starting-point of the delimitation
“at the base of the sand spit extending northwest from Isla Portillos, because no
reliable basepoints can be derived from this ephemeral low-lying feature. The coordinates
of the starting point in the Caribbean… are 10° 56' 26.0" N and
83° 41' 53.0" W” (Memorial of Costa Rica, para. 4.15).
114. In its Counter-Memorial, Nicaragua agrees that the starting-point of the maritime
boundary is “the point at which the line dividing the land territories of the two States intersects the
coast” (Counter-Memorial of Nicaragua, para. 3.34). It submits however that this point is to be found
about 3.6 km east of that suggested by Costa Rica (ibid., paras. 3.35, 3.48, 3.52). Recalling the 1858
Treaty of Limits, the 1888 Cleveland Award and the Alexander Awards, it considers that the
starting-point of the land boundary (and the maritime delimitation) is the extremity of Punta de
Castilla, which it places near the north-eastern corner of Los Portillos/Harbor Head Lagoon.
According to Nicaragua, the starting-point of the sea delimitation is located at 10° 55' 49.7'' North
and 83° 40' 0.6'' West (ibid., paras. 3.38-3.48, 3.52).
115. The present Report will therefore focus on the area situated between the two points
defined above. Their approximate location is shown in Figure 48 below.
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Figure 48. Annotated satellite image from June 2013 (Digital Globe; U.S.
Geological Survey) indicating the approximate location of the starting-points
of the maritime boundary proposed by Costa Rica (CR) and Nicaragua (N).
(1) Answer to the first question
116. In its Order of 31 May 2016, the Court first asked the authors of the present Report the
following question:
“(a) What are the geographical co-ordinates of the point at which the right bank of the
San Juan River meets the sea at the low-water line?”
117. As the sequence of sketches in Figure 44 illustrates, the position of the mouth of the San
Juan River experiences continuous variations, mainly related to changes in the spit of Isla Portillos,
i.e., westward growth by accumulation of sand and destruction by erosion (Figs. 46, 47). The growth
of the spit by sediment accretion is a progressive process, whereas its destruction, including the
opening of channels, may occur rapidly by strong waves (e.g., hurricanes) and floods of the San Juan
River. Consequently, the mouth of the San Juan River and its right bank are highly mobile.
118. The geographical co-ordinates of the point where the San Juan River meets the sea on the
right bank at the low-water line were measured by the topographers of both delegations during the
first and second site visits (Table 2). In the first site visit the point (Prmb) was measured on
6 December 2016 by both Parties on exactly the same point at 11:25-11:27 a.m. (low-tide time)
(Table 2; Fig. 49). In the second site visit the point (Prm2) was measured on 14 March 2017 by both
Parties on exactly the same point at 8:16-8:17 a.m. (low-tide time) (Table 2, Fig. 50). The distance
between both points is 670 m, indicating an average growth rate of 6.8 m/day.
6 December 2016 at 11:25-11:27 a.m. (first site visit)
Costa Rica 204966.090 E 1210750.500 N
Nicaragua 204965.88 E 1210750.48 N
14 March 2017 at 8:16-8:17 a.m. (second site visit)
Costa Rica 204365.52 E 1211066.66 N
Nicaragua 204365 E 1211067 N
Table 2. Geographical co-ordinates (WGS 1984) of the point at which the right
bank of the San Juan River meets the sea at the low-water line, measured during
the two site visits by the topographical teams of both Parties.
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Figure 49. Measurement of co-ordinates by Costa Rica (left) and Nicaragua (right) of the point at
which the right bank of the San Juan River (Prmb) meets the sea at low tide (6 December 2016,
at 11:25-11:27 a.m.).
Figure 50. Measurement of co-ordinates by Nicaragua (left) and Costa Rica (right) of the point at
which the right bank of the San Juan River (Prm2) meets the sea at low tide (14 March 2017, at
8:16-8:17 a.m.).
(2) Answer to the second question
119. In the Order of 31 May 2016, the second question put by the Court to the authors of the
present Report was:
“(b) What are the geographical co-ordinates of the land point which most closely
approximates to that identified by the first Alexander Award as the starting-point of the
land boundary?”
(a) The starting-point of the land boundary identified by the first Alexander Award
120. In order to answer the second question of the Court, we first have to recall some
historical and factual elements.
121. As indicated by the Court in the Judgment it rendered on 16 December 2015 in the cases
Certain Activities carried out by Nicaragua in the Border Area (Costa Rica v. Nicaragua) and
Construction of a Road in Costa Rica along the San Juan River (Nicaragua v. Costa Rica):
“[f]ollowing hostilities between the two States in 1857, the Governments of Costa Rica
and Nicaragua signed on 15 April 1858 a Treaty of Limits, which was ratified by Costa
Rica on 16 April 1858 and by Nicaragua on 26 April 1858 (hereinafter the ‘1858
Treaty’). The 1858 Treaty fixed the course of the boundary between Costa Rica and
Nicaragua from the Pacific Ocean to the Caribbean Sea.” (Judgment, para. 59)
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122. The Court also recalled that, according to Article II of the 1858 Treaty:
“‘The dividing line between the two Republics, starting from the Northern Sea [i.e. the
Caribbean sea], shall begin at the end of Punta de Castilla, at the mouth of the San
Juan de Nicaragua river, and shall run along the right bank of the said river up to a
point three English miles distant from Castillo Viejo . . .’ [In the Spanish original: ‘La
línea divisoria de las dos Repúblicas, partiendo del mar del Norte, comenzará en la
extremidad de Punta de Castilla, en la desembocadura del río de San Juan de
Nicaragua, y continuará marcándose con la margen derecha del expresado río, hasta
un punto distante del Castillo Viejo tres millas inglesas…’]” (Judgment, para. 71)
123. As the Court indicated,
“Following challenges by Nicaragua on various occasions to the validity of the 1858
Treaty, Costa Rica and Nicaragua signed another instrument on 24 December 1886,
whereby the two States agreed to submit the question of the validity of the 1858 Treaty
to the President of the United States, Grover Cleveland, for arbitration. In addition, the
Parties agreed that, if the 1858 Treaty were found to be valid, President Cleveland
should also decide ‘upon all the other points of doubtful interpretation which either of
the parties may find in the treaty’. On 22 June 1887, Nicaragua communicated to Costa
Rica 11 points of doubtful interpretation, which were subsequently submitted to
President Cleveland for resolution. The Cleveland Award of 1888 confirmed, in its
paragraph 1, the validity of the 1858 Treaty and found, in its paragraph 3 (1), that the
boundary line between the two States on the Atlantic side ‘begins at the extremity of
Punta de Castilla at the mouth of the San Juan de Nicaragua River, as they both existed
on the 15th day of April 1858’” (Judgment, para. 60)
124. As further indicated by the Court in its Judgment of 16 December 2015 (see para. 61),
subsequent to the Cleveland Award, Costa Rica and Nicaragua agreed in 1896, under the Pacheco-
Matus Convention on border demarcation, to establish two national Demarcation Commissions, each
composed of two members (Art. I). The Pacheco-Matus Convention further provided that the
Commissions would include an engineer, appointed by the President of the United States of
America, who “shall have broad powers to decide whatever kind of differences may arise in the
course of any operations and his ruling shall be final” (Art. II). United States General Edward Porter
Alexander was so appointed.
125. During the demarcation process, which began in May 1897 and was concluded in 1900,
General Alexander rendered five awards.
126. In his first Award, dated 20 December 1897, General Alexander stated that the boundary
line:
“must follow the . . . branch . . . called the Lower San Juan, through its harbor and into
the sea. The natural terminus of that line is the right-hand headland of the harbor
mouth.” (RIAA, Vol. XXVIII, p. 217.)
He then defined the initial part of the boundary starting from the Caribbean Sea in the following
terms:
“The exact spot which was the extremity of the headland of Punta de Castill[a] [on]
April 15, 1858, has long been swept over by the Caribbean Sea, and there is too little
concurrence in the shore outline of the old maps to permit any certainty of statement of
distance or exact direction to it from the present headland. It was somewhere to the
northeastward, and probably between 600 and 1,600 feet distant, but it can not now be
certainly located. Under these circumstances it best fulfills the demands of the treaty
- 45 -
and of President Cleveland’s award to adopt what is practically the headland of to-day,
or the northwestern extremity of what seems to be the solid land, on the east side of
Harbor Head Lagoon.
I have accordingly made personal inspection of this ground, and declare the initial line
of the boundary to run as follows, to wit:
Its direction shall be due northeast and southwest, across the bank of sand, from the
Caribbean Sea into the waters of Harbor Head Lagoon. It shall pass, at its nearest
point, 300 feet on the northwest side from the small hut now standing in that vicinity.
On reaching the waters of Harbor Head Lagoon the boundary line shall turn to the left,
or southeastward, and shall follow the water’s edge around the harbor until it reaches
the river proper by the first channel met. Up this channel, and up the river proper, the
line shall continue to ascend as directed in the treaty.” (Ibid., p. 220.)
127. A sketch illustrating this initial part of the boundary in the geographic situation prevailing
at the time was attached to this first Award (ibid., p. 221) (see Figure 51 below).
Figure 51. Printed sketch-map attached to Alexander’s First Award
128. Following this First Award, the proceedings of the Demarcation Commissions recorded
the co-ordinates of the starting-point of the land boundary by reference to the center of Plaza
Victoria in old San Juan de Nicaragua (Greytown) and other points on the ground (see further on this
below).
(b) Geographical co-ordinates of the land point which most closely approximates to that
identified by the first Alexander Award as the starting-point of the land boundary
129. The second question of the Court can be interpreted in two different ways:
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(i) First option
130. One alternative is to “adopt what is practically the headland of to-day, or the
northwestern extremity of what seems to be the solid land, on the east side of Harbor Head Lagoon”
as it exists in 2016-2017. This approach coincides with that followed in the first Alexander Award,
dated 20 December 1897.
131. Although the headland of Punta de Castilla has experienced significant retreat due to
coastal erosion (e.g., Fig. 22), it still exists as a geomorphic and geographical feature in the
landscape. The point that represents the northwestern extremity of relatively more solid land on the
east side of Los Portillos/Harbor Head Lagoon was identified and measured in the first site visit at
point Ple (Figs. 18, 27; Table 1). This spot is located at the contact between the relatively stable
surface covered by tree vegetation on the eastern margin of the lagoon (Fig. 23), and the
accumulation of easily erodible loose sand that forms the spit-barrier of Los Portillos/Harbor Head
Lagoon (Fig. 25). The spot in the shoreline at which the projection perpendicular to the coast of
point Ple meets the low-water line at low tide was measured in the second site visit by the
topographical teams of both parties on 15 March 2017 at 8:57 a.m. (point Pleb, Figs. 18, 35;
Table 1).
(ii) Second option
132. Another alternative is to adopt “the land point” as it exists today which is geographically
closest to the point identified by Alexander and the Demarcation Commissions as the starting-point
of the land boundary, which is now in the Caribbean Sea due to coastal erosion.
133. With regard to this second option, in a first stage we need to locate with modern
geographical co-ordinates the starting-point identified by Alexander and in the proceedings of the
Demarcation Commissions, whose position was defined in relation to several markers and points. In
a second stage we can determine the closest land point.
134. For the first of these stages, it is necessary to retrace a number of events.
a. Works of the Demarcation Commissions and General Alexander (1897-1899)
135. On 2 October 1897, the Demarcation Commissions, together with General Alexander,
“having proceeded with a personal inspection of the place designated by the arbiter as the initial
point of the boundary line... established the spot where the monument that will serve as a boundary
marker on the Atlantic Coast should be placed”. It is indicated that “the aforementioned spot is
provisionally marked by a straight line of three hundred English feet measured from the hut referred
to in the arbitral award and in the direction that will be stated further on” (Proceedings of the Costa
Rica-Nicaragua Demarcation Commissions (1897-1900), Proceedings VI, reproduced at Ann. 4 of
Nicaragua’s Counter-Memorial).
136. On 2 March 1898, the Demarcation Commissions “proceeded first and foremost to
emplace the Monument that determined the Initial Point of the dividing line on the Coast of the
Caribbean Sea, linking it with the center of Plaza Victoria in San Juan del Norte” (Proceedings of the
Costa Rica-Nicaragua Demarcation Commissions (1897-1900), Proceedings X, reproduced at
Ann. 5 of Nicaragua’s Counter-Memorial).
137. The location of the Initial Point or first marker was measured by triangulation with
respect to a marker placed in the center of Plaza Victoria in the old town of San Juan del Norte
(Greytown), taking that center as the origin (see Figure 52 below). The distance from the center of
Plaza Victoria to the Initial Marker was 4715.55 m with a geodetic azimuth of 244º 50' 23''
(measured in direction S-W-N-E). The text of the Proceedings indicates 244º 50' 23” and the sketch
244º 50' 25” for the azimuth between the marker of Plaza Victoria and the Initial Marker (Fig. 52).
- 47 -
Most probably the latter value was a clerical error introduced by the drafter, since the former one is
indicated repeatedly in the text.
138. Proceedings X of 2 March 1898 also indicate that it was agreed to place another reference
marker on the opposite margin of Los Portillos/Harbor Head Lagoon, at 1139 m from the Initial
Marker, with an azimuth of 66° 41' 05” (see point A/Am on Figure 52 below). The figure indicates
the azimuth measured from the other edge of the triangulation line 246° 41' 05”).
139. The markers located at the Initial Point and the center of Plaza Victoria had iron pipes
approximately 40 cm in diameter and 2 m long filled with concrete. The iron pipe of the marker
placed in the center of Plaza Victoria was buried so that its upper end appeared at ground level. The
proceedings indicate that this marker was located opposite to the place where the old church of San
Juan del Norte used to be situated, implicitly indicating that the church had already disappeared.
Figure 52. Sketch included in Proceedings X of the Costa Rica-Nicaragua Demarcation
Commissions, showing the relative co-ordinates of the Mojón Inicial (Initial Marker) with respect
to the marker placed in the center of Plaza Victoria.
140. Proceedings X also included a chart with co-ordinates for the first segment of the land
boundary, and a sketch showing that portion of the boundary and the location of the Initial Marker
(Mojón Inicial) (see Figure 53 below).
- 48 -
Figure 53. Sketch of the San Juan River and Los Portillos/Harbor Head
Lagoon showing the first segment of the land boundary and the location
of the Initial Marker (Proceedings X of the Costa Rica-Nicaragua
Demarcation Commissions).
141. On 3 June 1898, Andrés Navarrete, member of the Costa Rican Commission, took to
San Juan del Norte the piece of granite with four engraved bronze plates on its sides to be emplaced
at the location of the Initial Marker (Mojón Inicial). On 23 December 1898, this “piece of granite
was placed with the bronze plates on which the mandated inscriptions were engraved, and the points
of reference were built in Harbor Head and in Victoria Square, having fully complied with the
resolution of the Arbiter, General E. P. Alexander” (Proceedings of the Costa Rica-Nicaragua
Demarcation Commissions (1897-1900), Proceedings XIV and XV, reproduced at Anns. 6 and 7 of
Nicaragua’s Counter-Memorial).
142. On 13 June 1899, the Commissions recorded that “given the circumstance that the
monument that is the starting-point in Harbor Head has been tipped over by the sea and that both
Commissions wish to conserve the monument as the sign for beginning the line, they have arranged
to rebuild it at a point that can preserve it from invasions by the sea, and connecting it geodetically
with the point it previously occupied” (Proceedings of the Costa Rica-Nicaragua Demarcation
Commissions (1897-1900), Proceedings XVI, reproduced at Ann. 8 of Nicaragua’s Counter-
Memorial).
- 49 -
143. On 19 August 1899, recalling that the “initial marker, placed near Punta de Castilla, [had]
completely disappeared due to the force of the elements” and that they had “to preserve the position
of said Punta de Castilla and the initial marker by means that facilitate the exact placement of those
points at any given time”, the Commissions explained that:
“it is hereby agreed to build three masonry markers according to the map herein copied
[and reproduced below as Figure 54] and in the points marked by the triangulation
performed, according to the calculation and map surveyed for such purpose and
included in these Minutes.” (Proceedings of the Costa Rica-Nicaragua Demarcation
Commissions (1897-1900), Proceedings XX, reproduced at Ann. 9 of Nicaragua’s
Counter-Memorial)
144. The map includes the distances and azimuths of all the triangulation lines between the
following markers and points:
C: Punta de Castilla
I: Initial Marker (Mojón Inicial, destroyed by the sea)
A: Main Marker (Mojón Principal)
Am, A1: Auxiliary markers (Mojones auxiliares)
145. All the points of this new triangulation were related with the marker located in the center
of Plaza Victoria.
Figure 54. Triangulation measurements obtained in August 1899 between Punta de Castilla (C),
Initial Marker (I), Main Marker (A), and auxiliary markers Am and A1. Note that Punta de Castilla is
located 91.44 m to the NW (140º 52') of the Initial Marker (Proceedings XX of the Costa Rica-
Nicaragua Demarcation Commissions).
- 50 -
146. Proceedings XX described graphically two types of markers (Fig. 55 below):
 Modelo A for the Main Marker A;
 Modelo B for auxiliary markers Am and A1. The latter were buried 1.2 m in the ground,
were 2.25 m high, and their northern façade were engraved indicating the distance to
Punta de Castilla and the corresponding azimuth.
Figure 55. Sketch showing the geometrical features and
parameters of the two types of markers installed for
facilitating the exact placement of Punta de Castilla and the
Initial Marker at any given time (Proceedings XX of the
Costa Rica-Nicaragua Demarcation Commissions).
b. Works of the Sub-Commission on Limits and Cartography established by Costa Rica and
Nicaragua (2002-2005)
147. It is further important to recall that, on 6 September 2002, Costa Rica and Nicaragua
decided to reactivate the Sub-Commission on Limits and Cartography they contemplated in 1997 “to
begin conversations conducive to defining the maritime delimitation between both countries”
(Memorial of Costa Rica, Ann. 29 and 30).
148. This Sub-Commission of Limits and Cartography met on several occasions afterwards.
— Meeting of 25 March 2003 (Second meeting)
149. The Minute of the second meeting of the said Sub-Commission (dated 25 March 2003)
indicated that, with regard to the work for delimitation on the Caribbean Sea, “[t]he Sub-
Commission considered it necessary to work on documents to calculate with modern procedures the
co-ordinates of marker number one, based on the topographic survey created by Engineer Alexander
- 51 -
in 1900” (Minute of the Second Meeting of the Sub-Commission on Limits and Cartography,
25 March 2003, Memorial of Costa Rica, Ann. 32; Counter-Memorial of Nicaragua, Ann. 13).
— Meeting of 4 September 2003 (Third meeting)
150. The Minute of the third meeting (dated 4 September 2003) specified that the Nicaraguan
Institute of Territorial Studies (hereinafter “INETER”) had indicated, in a report, that “in the XXth
Minutes of the Alexander Commission of 1899, it is clear that Marker One had disappeared because
of the sea, thus a triangulation of markers was ordered to locate the initial point. During the visit of
21 February 20[0]3, both delegations found a marker at that triangulation” although it is not clear
which marker it was (Minute of the Third Meeting of the Sub-Commission on Limits and
Cartography, 4 September 2003, Memorial of Costa Rica, Ann. 33; Counter-Memorial of Nicaragua,
Ann. 14).
— Meeting of 24 to 27 November 2003 (Fourth technical meeting)
151. At its fourth technical meeting, held from 24 to 27 November 2003, the Sub-Commission
recorded that “[i]n compliance with the agreements of the Third meeting … on September 4, 2003,
the Technical Groups of Nicaragua and Costa Rica proceeded with the field Works to determine the
modern co-ordinates for Marker 1, which disappeared in 1899 due to the force of the sea” (Minute of
the Fourth Technical Meeting of the Sub-Commission on Limits and Cartography, 24-27 November
2003, Counter-Memorial of Nicaragua, Ann. 15).
152. It is indicated that, on 24 November 2003, the Nicaraguan technical team, “accompanied
by a guide — Mr. Hedly Thomas, who is familiar with the place … went toward San Juan del Norte
(Greytown), to locate one of the key points of the triangulation that Engineer and Arbiter Alexander,
carried out in 1897; this point was called by the Arbiter, ‘The Center of Victoria Square’, and was
marked at such time with a 40 cm diameter iron rod filled with concrete and buried 2 meters deep”.
Since the guide assured that the rod was covered by very thick undergrowth, it was decided to clean
the area. Nevertheless, the rod could not be found on that day. On 26 November 2003, a delegation
from both States used metal detectors but still could not find the rod (ibid.).
153. The Minute further indicated that, on 25 November 2003, a marker was located at Los
Portillos/Harbor Head Lagoon (Fig. 56). This marker was reported as the “First Marker”. It was
measured by both Parties for 2:50 hours with hand-held GPS devices and
“an excavation was also performed around the landmark, where one of the sides was
marked with a letter ‘A’ accompanied by another illegible symbol, confirming that the
dimensions are the same … as the design of the type A boundary landmarks for the
demarcation of limits between Nicaragua and Costa Rica of 1897, pursuant to the
Minutes of Arbiter E. P. Alexander.” (the original Spanish reads as follows: “una
excavación en el contorno del mismo, en donde se descubrió en uno de sus lados la
letra ‘A’ acompañada de otro símbolo ilegible, confirmando que las dimensiones son
iguales al diseño del modelo tipo A de los mojones fronterizos para los trabajos de
demarcación de limites entre Nic. y C.R. de 1897 conforme a las Actas del Arbitro E.P.
Alexander.”) (Ibid.)
154. It was further stipulated that this Marker “is the same one located during the first
technical visit to Punta [de] Castilla, which took place on February 21, 2003.” (Ibid.)
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Figure 56. Marker found in the beach by the Sub-
Commission on Limits and Cartography on 21
February 2003 and on 25 November 2003. The
side exposed by the excavation was marked with a
letter “A” accompanied by another illegible
symbol. This marker was measured by both Parties
for 2:50 hours with hand-held GPS devices.
155. The Minute then recorded that, on the same day (25 November 2003), the Costa Rican
delegation found another marker on the right/east bank of the Los Portillos/Harbor Head Lagoon,
which was engraved on one of its sides with “the letter ‘A2’” (Figs. 3, 32).
156. On 26 November 2003, a third marker was found, of “Model Type A… inclined and
submerged in Los Portillos Lagoon by approximately 98 mt, to the south of the first Marker found on
the coast on Tuesday, November 25” (ibid.) (Fig. 57). Nicaragua measured the co-ordinates of this
marker with a hand-held GPS device (83º 40’ 24.4’’N, 10º 56’ 2.3’’W).
Figure 57. Submerged marker found on 26 November 2003 in Los
Portillos/Harbor Head Lagoon. Co-ordinates were measured by
Nicaragua with a hand-held GPS.
- 53 -
— Meeting of 30 June 2005
157. At the meeting of the Sub-Commission of Limits and Cartography held on 30 June 2005,
INETER presented a report on the “Calculation of the geodesic position of Marker one from the land
border between Nicaragua and Costa Rica”, based on “the location of Marker A2 which was found in
restorable conditions, 100 years after its installation” (Minute of the Fourth Meeting of the Sub-
Commission on Limits and Cartography, 30 June 2005, Memorial of Costa Rica, Ann. 36). The
Minute explained that:
“Said Marker will serve to determine the geodesic position of the starting point
(Marker 1), in addition to the placement of the marker on the coast, which is linear with
Marker A2 and Marker 1.” (Ibid.)
158. The report mentioned in the minute is not, however, part of the documents communicated
to the authors of the present Report.
*
c. First investigation phase
159. In light of the above, in the initial phase of our investigation we tried to determine the
geographical co-ordinates of the Initial Marker (Mojón Inicial) using any of the markers and the
triangulation measurements (azimuths and distances) recorded in the Proceedings X and XX of the
Costa Rica-Nicaragua Demarcation Commissions (Figs. 34, 36). It is indispensable to know the
precise location of at least one the markers to apply this approach. However, it had to be ruled out
since we were not able to find any of the markers, as explained below:
Marker “A2” located on the eastern edge of Los Portillos/Harbor Head Lagoon (see para. 155 of the
present Report, and Figs. 3, 32)
160. This conspicuous monument was examined during the first and second site visits. It is
engraved with a “Δ” or an “A” and a symbol similar to a reversed “s” as subscript on its western side
and cannot be ascribed to any of the markers recorded in the Proceedings of the Costa Rica-
Nicaragua Demarcation Commissions (Fig. 58). It could be an unrecorded monument emplaced in
more recent times.
- 54 -
Figure 58. Inscription on the western side of the monument
located on the eastern side of Los Portillos/Harbor Head
Lagoon. Image taken during the first site visit (7 December
2016).
Marker found in the beach by the Sub-Commission on Limits and Cartography on 21 February 2003
and on 25 November 2003 and marked with a letter “A” accompanied by another illegible symbol
(Fig. 56)
161. This marker was measured by both Parties for 2:50 hours with hand-held GPS devices.
The Parties provided to the authors of this Report the co-ordinates measured by Nicaragua (10º 56’
1’’ N, 83º 40’ 23’’ W) and Costa Rica (10º 56’ 5’’ N, 83º 40’ 22’’ W), as well as the average coordinates
(10º 56’ 03’’ N, 83º 40’ 22.5’’ W).
162. During our first site visit we located the average geographical co-ordinates in the sea, at
some distance from the shore. Assuming that the marker found could correspond to auxiliary marker
Am, and using the average co-ordinates as well as the distance and azimuth between auxiliary
markers Am and A1 (45 m, 319º 22’) (Fig. 54), we located the probable position of marker A1 in a
spot situated on the beach, close to the swash zone of the waves. The upper semicircular area of 15 m
radius about this point was investigated by probing using iron rods with limited penetration (ca.
0.5 m), without obtaining a satisfactory result (Fig. 59).
163. Between the first and second site visits, the projection of the different geographical coordinates
on a georeferenced satellite image of 2003 revealed that the co-ordinates measured by
Costa Rica were the most reliable, since they were the only ones that fell on the beach (Fig. 60).
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164. In the second site visit, the co-ordinates of Costa Rica (10º 56’ 5’’ N, 83º 40’ 22’’ W)
were located around 100 m off the shoreline, indicating significant coastal retreat between 2003 and
2017. Consequently, the possibility of looking for this marker at a spot currently submerged under
the sea was discarded.
Figure 59. Investigation by probing in an area around the point estimated for the
location of marker A1, assuming that the marker found in the beach in 2003 was
marker Am and the average co-ordinates were the best approximation for its
location. Image taken on 9 December 2016 during the first site visit.
Figure 60. Projection on a satellite image from 2003 of the co-ordinates measured by Nicaragua
and Costa Rica for the markers found in 2003 in the beach (square representing average coordinates
and triangles the measurements of the Parties) and submerged in the lagoon (yellow
circle).
- 56 -
Marker found on 26 November 2003 submerged in Los Portillos/Harbor Head Lagoon and measured
by Nicaragua with a hand-held GPS device (83º 40’ 24.4’’N, 10º 56’ 2.3’’W) (Fig. 57)
165. During the second site visit, we investigated the area around the co-ordinates provided by
Nicaragua for this marker using three approaches:
(1) Metal detector of the Nicaraguan delegation, despite the fact that the Proceedings of the
Costa Rica-Nicaragua Demarcation Commissions do not specify whether the auxiliary
markers were built with any iron element;
(2) GPR of the Costa Rican delegation (GSSI system with shielded 400 MHz antenna),
acquiring a total of 12 profiles 27 m long (Fig. 61). These profiles with a spacing of 2 m,
covered a rectangular area of around 600 m2 (co-ordinates of corners:
207793.287/1209974.172; 207777.644/1209958.519; 207771.856/1209990.760;
207757.174/1209974.547; see Figure 18). The spacing of the profiles was adequate to
detect a buried marker 0.8-1.2 m wide (see Figure 55), since the GPR system investigates
a band that widens with depth. The width of the investigation footprint at a depth of 2 m
would be around 0.8 m, considering a velocity of 0.1 m/ns for the propagation of the
electromagnetic waves in sand (Conyers and Goodman, 1997; Neal, 2004). The GPR data
was processed in the field and the anomalies were investigated by excavating a circular
pit of about 2 m in diameter and driving in the ground iron rods 2 m long at a spacing of
around 0.4 m. This approach did not provide a satisfactory result;
(3) A large area, mostly including the one previously investigated with the GPR (Fig. 18), was
prospected perforating the ground with the 2 m long iron probes at a spacing of around
0.4 m (Fig. 62). The co-ordinates measured along the perimeter of the surveyed area are
indicated in table 1 (Pp1-Pp13 of Nicaragua and Pp1-Pp9 of Costa Rica). In the upper
part of the beach the ground was lowered around 1 m by excavating with shovel before
using the probes. The few spots where the rods could not pierce the sand were checked by
excavating with shovel without finding any sign of the marker.
Figure 61. GPR survey carried out in an area enclosing the co-ordinates measured
by Nicaragua for the marker found in 2003 submerged in Los Portillos/Harbor
Head Lagoon. A total of 12 GPR profiles 27 m long were acquired with a spacing
of 2 m. Pink flags indicate the starting and end points of the profiles.
- 57 -
Figure 62. Partial view of the area investigated with GPR, metal detector
and iron rods around a point established with the co-ordinates measured
in 2003 by Nicaragua for the marker found submerged in the water. The
sticks driven into the sand, with a spacing of around 0.4 m, mark the
points investigated by probing with 2 m long iron rods. Excavations were
carried out at the location of the GPR and metal-detector anomalies, as
well as along the higher part of the beach, in order to introduce the probes
at a lower elevation and increase the investigation depth.
Marker placed in the center of Plaza Victoria built with an iron pipe 40 cm in diameter and 2 m long
fully embedded in the ground
166. The approximate location of this marker was estimated by georeferencing several
historical maps (explained below). On the basis of the results of this analysis we defined an
investigation area in the airport of San Juan del Norte, including a 180 m long section of the airstrip
and the adjacent 25 m wide bands on both sides bounded by the airport fences. The co-ordinates of
the corners of this investigation area (ca. 13,500 m2) are indicated in Table 1 (points PairNE, PairSE,
PairNW, PairSW, see Figure 9).
167. The whole area was investigated with the metal detector provided by the Nicaraguan
delegation (Fig. 63). All the anomalies, except those found in the airstrip made of reinforced
concrete, were checked by excavating with pick and shovel. A large number of metal objects were
found buried in the ground as deep as 0.8 m.
168. The whole area was investigated with the GPR provided by the Nicaraguan delegation,
except a 60 m x 25 m zone associated with the SW corner of the investigation area due to problems
with the batteries (co-ordinates: 204437/1208455, 204377/1208460, 204436/1208435,
204374/1208433, see figure 9).
169. The GPR profiles could show diffraction hyperbolas or local lateral changes in the
diffraction pattern related to the iron rod of the marker or the foundation of the marker, respectively.
The performance of this shallow geophysical technique is adversely affected by the presence of
vegetation, clay, sediments with high moisture content and a shallow water table. The GPR data was
acquired with a GSSI system and a 200 MHz antenna, adequate for the purpose of our investigation
(Fig. 64). A total of 136 profiles were collected with a spacing of 1.55 m and an aggregate
investigation length of 8.16 km.
- 58 -
170. This method proved very ineffective mainly due to the shallow water table, intercepted in
some test pits at depths between 0.3 and 0.7 m, as well as the high moisture content and dense weed
at the surface. Nonetheless, the anomalies identified in the GPR profiles were checked with the metal
detector and by manual excavations obtaining negative results.
171. This investigation strongly suggested that the marker of Plaza Victoria was located in the
area nowadays covered by the airstrip and that it was removed during the construction of the airport.
Figure 63. Survey with the metal detector of Nicaragua of the selected
180 m long portion of the airstrip at San Juan del Norte. Image taken
during the second site visit on 13 March 2017.
Figure 64. Prospecting for the marker of Plaza Victoria in the airstrip of the San
Juan del Norte airport with a GPR (Ground Penetrating Radar) of the Nicaraguan
delegation using a 200 MHz shielded antenna. The vegetation in the northern flank
of the airstrip was being cleared for GPR and metal detector surveying. Image
taken during the second site visit on 13 March 2017.
- 59 -
d. Second investigation phase
172. Given that we were not able to find any of the markers recorded in the Proceedings of the
Demarcation Commissions, the best approach for identifying the land point which most closely
approximates the estimated position of the Initial Marker (Mojón Inicial) is: (1) locating the position
of the center of Plaza Victoria by georeferencing historical maps; (2) calculating the location of the
Initial Marker (Mojón Inicial) using the triangulation data of Proceedings X (distance of 4715.55 m
and a geodetic azimuth of 244º 50' 23'' measured counter-clockwise); and (3) determining the land
point closest to this location.
i. Location of the center of Plaza Victoria
173. The geographic co-ordinates in the WGS84 system of the center of Plaza Victoria have
been estimated using two historical maps:
— Map of Greytown Harbor of 1899, produced by the Nicaragua Canal Commission
(provided by Costa Rica on 20 October 2016, Fig. 65). This map was selected because it
includes co-ordinates, has sufficient degree of detail, is contemporaneous to the sketches
included in the Proceedings of the Costa Rica-Nicaragua Demarcation Commissions
(1987-1900), and shows the configuration of Greytown in concurrence with the Map of
Greytown of 1888 (provided by Nicaragua on 20 October 2016, Fig. 66).
— Map of Greytown of 1888, in which Plaza Victoria is clearly visible and labeled (Fig. 66).
174. These historical maps have inaccuracies and distortions related to the old mapping
techniques used, the scarcity of stable reference points in the constantly changing coastal
environment, the varying mapping scales, and the distortion of the paper on which they were drafted.
However, they provide sufficient information for locating the center of Plaza Victoria with an
acceptable degree of accuracy for the objectives of our report.
175. Initially, the Map of Greytown Harbor of 1899 was georeferenced and imported to
WGS84 and UTM 17N using already georeferenced basemaps and assigning co-ordinates to Ground
Control Points (GCPs, common points recognizable in the already georeferenced basemaps and the
map that needs to be georeferenced).
176. The main basemap used in this georeferencing step was the Map of San Juan del Norte of
1966, produced by the US Army using aerial photographs taken in 1960 (provided by Nicaragua and
Costa Rica on 20 October 2016, Fig. 67). This map was previously georeferenced in NAD27 (North
America Datum of 1927) and converted to WGS84 with ArcGIS v10.3 software. We also used as a
basemap the satellite image of 18 December 2009 acquired by RapidEye sensor, which was already
georeferenced when purchased from Digital Globe (Fig. 68).
177. The Map of Greytown Harbor of 1899 was georeferenced selecting eight GCPs (Fig. 69)
and applying a linear (affine) transformation, obtaining a total Root Mean Square (RMS) error of
12.46 m. Despite the low number of GCPs and their uneven distribution, mostly concentrated in the
western part of the map, the georeferencing was acceptable as indicated by the spatial correlation
between the natural and man-made features represented in the 1899 Map of Greytown Harbor and
the corresponding ones in the basemaps (Figs. 70, 71, 72, 73). The reliability of the georeferencing is
also supported by the alignment of the co-ordinates measured in the site visits along the northern
boundaries of the cemeteries with the southern edge of a street (Fig. 71), and the northern edge of the
high vegetation south of the landing strip of San Juan del Norte Airport (Fig. 73).
- 60 -
Figure 65. Georeferenced Map of Greytown Harbor of 1899, produced by the Nicaragua Canal
Commission.
Figure 66. Georeferenced Map of Greytown of 1888 showing the center of Plaza Victoria and the
corners of the cemeteries measured with GPS by the Parties.
- 61 -
Figure 67. Georeferenced Map of San Juan del Norte of 1966 produced by the US Army, used as
basemap for georeferencing the Map of Greytown Harbor of 1899.
Figure 68. Georeferenced satellite image of 18 December 2009 acquired by RapidEye sensor, used
as basemap for georeferencing the Map of Greytown Harbor of 1899.
- 62 -
Figure 69. Ground Control Points used for georeferencing the Map of
Greytown Harbor of 1899 (top) using as basemaps the Map of San Juan del
Norte of 1966 (center) and a satellite image from 2009 (bottom).
- 63 -
Figure 70. Transparent overlay of the Map of Greytown Harbor of 1899 on the Map of San Juan del
Norte of 1966 with the corners of the cemeteries measured by the Parties, depicting the estimated
center of Plaza Victoria.
Figure 71. Transparent overlay of the Map of Greytown Harbor of 1899 on the Map of
San Juan del Norte of 1966 showing the alignment of the corners of the cemeteries
measured by the Parties with a street (enlargement of the previous figure).
- 64 -
Figure 72. Transparent overlay of the Map of Greytown Harbor of 1899 on the satellite image of 2009
with the corners of the cemeteries measured with GPS by the Parties, depicting the estimated center of
Plaza Victoria.
Figure 73. Transparent overlay of the Map of Greytown Harbor of 1899 on the satellite
image of 2009 showing the alignment of the corners of the cemeteries measured with
GPS by the Parties with the linear edge of the high vegetation south of the landing strip
(enlargement of the previous figure).
178. The validity of the georeferencing was also checked using the map of Punta de Castilla of
1988 by the Instituto Geográfico Nacional of Costa Rica (produced with aerial images of 1961 and
updated with images of 1987), which was georeferenced in NAD27 and converted to WGS84
- 65 -
(provided by Costa Rica and Nicaragua), the aerial images of 1961 and 1987 provided by Nicaragua,
and the aerial image of 1961 provided by Costa Rica (Fig. 74). These aerial images were previously
georeferenced using the satellite images of 2009 and 2016 obtained from Digital Globe.
Figure 74. Transparent overlay of the Map of Greytown Harbor of 1899 on the aerial photograph of
1961 provided by Costa Rica, with the corners of the cemeteries measured with GPS by the Parties,
depicting the estimated center of Plaza Victoria.
179. The precise position of the center of Plaza Victoria was estimated by georeferencing the
Map of Greytown of 1888 (Fig. 66) using the previously georeferenced Map of Greytown Harbor of
1899 as a basemap. The configuration of the urban area is quite similar on both maps. The
georeferencing was implemented using 20 evenly distributed GCPs in the urban area (Fig. 75) and
applying a linear transformation, resulting in a total RMS error of 3.44 m.
180. The centroid of Plaza Victoria was positioned at 10°55'12.462"N, 83°42'12.413"W in
WGS84, which is 204483.237 Easting, 1208469.486 Northing in UTM 17N. This point is located in
the landing strip of San Juan del Norte, within the central sector of the area investigated with GPR
and metal detector during the second site visit. An error margin of 20 m can be approximately
estimated for these co-ordinates considering the accumulated errors of the two georeferencing steps
and the errors associated with the historical maps (inaccuracies, distortion, scale). Overlays of the
georeferenced Map of Greytown of 1888 on the 1961 aerial image (provided by Costa Rica on
20 October 2016) (Figs. 76, 77) and the 2009 satellite image (Figs. 78, 79) are shown below.
- 66 -
Figure 75. Map of Greytown of 1888 (top) and Map of Greytown Harbor of 1899 (bottom)
indicating the 20 GCPs used for georeferencing the 1888 map and depicting the estimated
location of the center of Plaza Victoria.
- 67 -
Figure 76. Transparent overlay of the georeferenced Map of Greytown of 1888 on a
georeferenced aerial photograph of 1961, with the corners of the cemeteries measured by the
Parties and the estimated center of Plaza Victoria.
Figure 77. Transparent overlay of the georeferenced Map of Greytown of 1888 on a georeferenced
aerial photograph of 1961, with the corners of the cemeteries measured by the Parties and the
estimated center of Plaza Victoria (enlargement of the previous figure).
- 68 -
Figure 78. Transparent overlay of the georeferenced Map of Greytown of 1888 on the
georeferenced satellite image of 2009 with the corners of the cemeteries measured by the Parties
and the estimated center of Plaza Victoria.
Figure 79. Transparent overlay of the georeferenced Map of Greytown of 1888 on the
georeferenced satellite image of 2009 with the corners of the cemeteries measured by the parties
and the estimated center of Plaza Victoria (enlargement of the previous figure).
- 69 -
ii. Location of the Initial Marker (Mojón Inicial)
181. The co-ordinates of the Initial Marker (Mojón Inicial) were calculated using the Cartesian
co-ordinates (4268.28 m. East, 2004.54 m. North) and polar co-ordinates (distance 4715.55 m., south
azimuth 244°50'23") from the center of Plaza Victoria indicated in Proceedings X of the
Demarcation Commissions (Fig. 52). The co-ordinates calculated for the Mojón Inicial are
10°56'18.898"N, 83°39'52.536"W in WGS84, corresponding to 208751.395 Easting, 1210474.312
Northing in UTM 17N (Fig. 80).
182. The co-ordinates of the rest of the points depicted in the triangulation sketch included in
Proceedings X were also calculated following the same approach.
183. Subsequently, we calculated the co-ordinates of Punta de Castilla using the triangulation
data between the Initial Marker and Punta de Castilla indicated in Proceedings XX of the
Demarcation Commissions (Fig. 81). The co-ordinates calculated for Punta de Castilla are
10°56'21.191"N, 83°39'54.44"W in WGS84, corresponding to 208694.17 Easting, 1210545.321
Northing in UTM 17N. The error margin associated with the location of these points can be grossly
estimated at 20 m.
Figure 80. Transparent overlay of the sketch of Proceedings X of the Costa Rica-Nicaragua
Demarcation Commissions (1897-1900) on the satellite image of 2009. The overlay was produced
using the co-ordinates calculated for the center of Plaza Victoria and the triangulation data
included in Proceedings X.
- 70 -
Figure 81. Triangulation sketch included in Proceedings XX of the Costa Rica-Nicaragua
Demarcation Commissions (1897-1900) projected on a Worldview image of 2016. I stands for
Initial Marker and C for Punta de Castilla.
iii. Land point which most closely approximates the Initial Marker
184. The closest land points to the locations estimated for the Initial Marker and Punta de
Castilla have been determined using the most recent available satellite image of 22 January 2016.
The closest land point to the Initial Marker is located at a distance of 909 m on the spit-barrier of Los
Portillos/Harbor Head Lagoon at 10°56'18.898"N, 83°39'52.536"W in WGS84, or 208751.398
Easting, 1210474.305 Northing in UTM 17N (Figs. 82, 83). The closest land point to Punta de
Castilla is located at a distance of 941 m on the spit-barrier of Harbor Head/Los Portillos Lagoon at
10°55'54.122"N, 83°40'8.93"W (WGS84), or 208246.568 Easting, 1209716.975 Northing in UTM
17N (Figs. 84, 85). The error margin in the location of those points is equivalent to the error margin
estimated for the positioning of the Initial Marker and Punta de Castilla. Nonetheless, the position of
the closest land points changes due to the frequent variations in the spit-barrier of Los
Portillos/Harbor Head Lagoon.
- 71 -
Figure 82. Distances between the location estimated for the Initial Marker to the closest
land point on a satellite image from 22 January 2016 and points Plw and Ple measured
during the first site visit.
Figure 83. Distances between the location estimated for the Initial Marker to the closest
land point on a satellite image from 22 January 2016 and points Plw2 and Ple2
measured during the second site visit.
- 72 -
Figure 84. Distances between the location estimated for Punta de Castilla to the closest land
point on a satellite image from 22 January 2016 and points Plw and Ple measured during the
first site visit.
Figure 85. Distances between the location estimated for Punta de Castilla to the closest land
point on a satellite image from 22 January 2016 and points Plw2 and Ple2 measured during the
second site visit.
- 73 -
(3) Answer to the third question
185. In the Order of 31 May 2016, the third question put by the Court to the authors of the
present Report read as follows:
“(c) Is there a bank of sand or any maritime feature between the points referred to in
subparagraphs (a) and (b) above? If so, what are their physical characteristics? In
particular, are these features, or some of them, permanently above water, even at high
tide? Is Los Portillos/Harbor Head Lagoon separated from the sea?”
186. Between the points referred to in questions (a) and (b), we have identified the following
geomorphic features (described in section II.2) along the coastline during our site visits and using
satellite images from multiple dates (Table 3, Fig. 21):
Acquisition date Satellite sensor Spatial Resolution (m)
18 December 2009 RapidEye 5
10 March 2011 Worldview2 0.5
26 November 2013 Worldview2 0.5
4 March 2014 Worldview2 0.5
26 September 2014 Worldview2 0.5
22 January 2016 Worldview3 0.5
Table 3. Satellite images provided by Digital Globe.
— The sand spit-barrier that encloses or semi-encloses the Los Portillos/Harbor Head
Lagoon (Figs. 24, 25, 33, 37)
187. The observations carried out during out site visits and the available data (e.g., satellite
images, aerial photos) indicate that Los Portillos/Harbor Head Lagoon is commonly separated from
the sea by the sand barrier. However, high energy waves related to storms or hurricanes can breach
temporary channels in the barrier or in the beach allowing surface water circulation between the
lagoon and the sea (Figs. 29, 30, 31, 36, 37).
188. During our first visit, Los Portillos/Harbor Head Lagoon was draining towards the sea
through a channel breached around 200 m west of the northwestern corner of the lagoon, most
probably opened by Hurricane Otto, which made landfall in the area on 24 November 2016
(Figs. 29, 30, 31).
189. During our second visit, the channel was closed (Fig. 36). The extent of the sand barrier
is determined by the extent of the water body of the Los Portillos/Harbor Head Lagoon, which
experiences slight changes governed by variations in the water level. The western edge of the lagoon
and the sand barrier was measured during the first and second site visits, respectively, at points Plw
(highest water level reached after Hurricane Otto; Fig. 28) and at Plw2 (Fig. 34). The eastern edge of
the lagoon and the sand barrier were measured in the first and second site visits at points Ple
(Fig. 27) and Ple2 (Fig. 32), respectively. Point Pleb (Fig. 35), measured in the second site visit,
represents approximately the intersection between the shoreline at low tide and the projection of the
northeastern corner of the Los Portillos/Harbor Head Lagoon perpendicular to the coast.
— The coastal stretch of the portion of land designated in this Report as Isla Portillos and
its beach (Fig. 21), which can be divided into three main sections with different
characteristics, from east to west:
(1) West of the northwest corner of Los Portillos/Harbor Head Lagoon there is section which
was largely affected by active retreat in the first visit, including the channel that drained
the lagoon (Figs. 39, 40);
- 74 -
(2) West of point 17P 0207176E 1210255N (WGS1984), the coast is made up of a broad
sandy beach with discontinuous and coast-parallel enclosed lagoons in the backshore
(Figs. 41, 42);
(3) In the westernmost portion, close to the mouth of the San Juan River, there are no lagoons
with free-standing water in the backshore (Fig. 43).
190. Off the coastline, there are no features above water even at low tide, as it was observed
during the two site visits. Some satellite images reveal the presence of coast-parallel shoals. These
are the typical submerged sand bars that develop in the nearshore zone of sandy beaches by wave
action.
(4) Answer to the fourth question
191. In its Order of 31 May 2016, the Court finally asked the authors of the present Report the
following question:
“(d) To what extent is it possible, or probable, that the area concerned will undergo
major physical changes in the short and long term?”
192. Multiple lines of evidence clearly indicate that the coast has experienced a rapid retreat in
historical and contemporaneous times:
— General Alexander, in his first Award dated 20 December 1897, stated that “[t]he exact
spot which was the extremity of the headland of Punta de Castill[a] [on] April 15, 1858,
has long been swept over by the Caribbean Sea, and there is too little concurrence in the
shore outline of the old maps to permit any certainty of statement of distance or exact
direction to it from the present headland. It was somewhere to the northeastward, and
probably between 600 and 1,600 feet distant, but it can not now be certainly located.”
— On 13 June 1899, the Costa Rica-Nicaragua Demarcation Commissions recorded that “the
monument that is the starting point in Harbor Head has been tipped over by the sea”
(Proceedings of the Costa Rica-Nicaragua Demarcation Commissions (1897-1900),
Proceedings XVI, reproduced at Ann. 8 of Nicaragua’s Counter-Memorial). That
monument had been placed on 23 December 1898 (Proceedings of the Costa Rica-
Nicaragua Demarcation Commissions (1897-1900), Proceedings XIV and XV,
reproduced at Anns. 6 and 7 of Nicaragua’s Counter-Memorial).
— The cartographic sketch included in Proceedings X of the Costa Rica-Nicaragua
Demarcation Commissions from 1898 was georeferenced in WGS84 using the coordinates
calculated for the Initial Marker and the Cartesian and polar co-ordinates
included in the Proceedings. The comparison of the georeferenced sketch with a satellite
image from 2009 allows to roughly estimate a coastal retreat of 940 m on the east side of
Los Portillos/Harbor Head Lagoon, yielding an average recession rate of around 8.5 m/yr
(Fig. 86).
- 75 -
Figure 86. Overlay of the georeferenced sketch of Proceedings X of the Costa Rica-
Nicaragua Demarcation Commissions from 1899 on a satellite image acquired in 2009,
showing a coastal retreat of around 940 m on the eastern side of Los Portillos/Harbor Head
Lagoon.
— Figure 87 illustrates the position of the coastline mapped using satellite images from
different dates (1940, 1961, 1981, 1987, 2002, 2009, 2016). It shows an overall rapid
recession of the coastline.
- 76 -
Figure 87. Satellite image from 2016 showing the position of the coastline
mapped with images from multiple dates (1940, 1961, 1981, 1987, 2002, 2009,
2016).
193. This rapid coastal retreat is probably caused or favoured by the substantial reduction in
discharge of the San Juan River at the expense of the Colorado River in 1861 (González, 1994). It is
very likely that this trend will remain in the short and long term and that the coast will be affected by
further retreat. The main physical changes that may result from the currently active coastal recession
include:
(1) Reduction in the extent of Los Portillos/Harbor Head Lagoon, and eventually its
disappearance;
(2) Eastward shift of the San Juan River mouth of around 1 km as a result of the eventual
intersection between the coastline and the outer side of a meander currently located at ca.
300 m from the coast (Fig. 88).
Figure 88. Hypothetical scenario considering a general 300 m retreat of the
coastline. The mouth of the San Juan River could shift around 1 km to the east.
- 77 -
194. The spit of Isla Portillos at the mouth of the San Juan River will be affected by
continuous changes like in the previous decades (Fig. 44) and as documented in our site visits
(Figs. 46, 47). Most probably there will be periods of sediment accumulation and spit growth and
periods of spit destruction mainly related to erosion caused by strong waves and fluvial currents.
Such alterations in the spit will be accompanied by shifts in the position of the San Juan River
mouth.
195. Other potential physical changes to take into consideration include sharp deviations in the
path of the San Juan River (avulsion) taking advantage of secondary channels (caños) located on its
right margin in Isla Portillos and the topographic depression of Los Portillos/Harbor Head Lagoon
(i.e. the lagoon might become the mouth of the river).
* *
*
This Report was drawn up in English in one copy on 30 April 2017.
Eric Fouache Francisco Gutiérrez
___________
- 78 -
REFERENCES
Alvarado, L.F., Alfaro, E.J. (2003). Frecuencia de los ciclones tropicales que afectaron a Costa Rica
durante el siglo XX. Top. Meteoro. Oceanog., 11, 1-11.
Bergoeing, J.P. (2014). Geomorfología regional de Costa Rica. Gerüst Creaciones, 263 p.
Conyers, L.B., Goodman, D. (1997). Ground-Penetrating Radar: An Introduction for Archeologists.
Altamira Press. London.
González, C. (1994). Temblores, terremotos, inundaciones y erupciones volcánicas en Costa Rica
(1608-1910). Editorial Tecnológica de Costa Rica, Cartago, 239.
National Hurricane Center (2017). Hurricane Otto, 20 – 26 November 2016. Tropical Cyclone
Report, 26 p.
Neal, A. (2004). Ground-penetrating radar and its use in sedimentology: principles, problems and
progress. Earth-Science Reviews, 66, 261-330.
Nieuwenhuyse, A., Kroonenberg, S.B. (1994). Volcanic origin of Holocene beach ridges along the
Caribbean coast of Costa Rica. Marine Geology, 120, 13-26.
Parkinson, R.W., Cortés, J., Denyer, P. (1998). Passive margin sedimentation on Costa Rica’s North
Caribbean coastal plain, Río Colorado. Rev. Biol. Trop, 46, Supl. 6, 221-236.
Rabella, J. (2004). Aproximación a la Historia del Río San Juan. MARENA, Managua, 98 p.
Scheffers, A., Browne, T. (2010). Caribbean Coasts, Panama to Belize. In: Bird, E.C.F. (Ed.),
Encyclopedia of the World’s Coastal Landforms. Springer, 265-267.
*
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LIST OF FIGURES
Number Title Page
Figure 1 Annotated satellite image from December 2011 (U.S. Geological
Survey) showing the location of San Juan del Norte village, Río Indio
Lodge, the airport of San Juan del Norte built where Greytown used
to be located, the San Juan River and its mouth (its position is highly
variable), Isla Portillos, and the Los Portillos/Harbor Head Lagoon.
3
Figure 2 Drainage channel encountered during the first site visit, in which
water was draining from the Los Portillos/Harbor Head Lagoon to the
sea.
4
Figure 3 Image taken on the eastern corner of
Los Portillos/Harbor Head Lagoon, showing the marker known as
“A2”.
4
Figure 4 Steps presented by Nicaragua as possibly being those of the church
that would have been built on Plaza Victoria. Arrows indicate the
orientation of the stairs, ascending to the south (co-ordinates
measured with a hand-held GPS: 17P 0204495E, 1208408N).
6
Figure 5 Sketch-map included in Proceedings XX of the
Costa Rica-Nicaragua Demarcation Commissions (1897-1900),
showing the location of Punta de Castilla and auxiliary markers Am
and A1, as well as their relative positions indicated by distances and
azimuths
7
Figure 6 Exploration area around a point established assuming that the
average of the co-ordinates measured on 25 November 2003
correspond to the location of auxiliary marker Am and using the
triangulation values indicated in the sketch-map included in
Proceedings XX of the Costa Rica-Nicaragua Demarcation
Commissions (1897-1900).
8
Figure 7 Row of delegates probing of the sand with iron rods. 9
Figure 8 Museum of San Juan del Norte. 10
Figure 9 Area of the airport with locations of the corners of the cemeteries, the
area of the airport that was investigated and the church steps
presented by Nicaragua.
11
Figure 10 Placing of colored ribbons every 1.55 m on the cords marking off the
eastern and western extremities of the initial research area, covering a
60 m long section of the landing strip.
12
- 80 -
Number Title Page
Figure 11 Acquisition by Nicaragua of GPR profiles using a GSSI system
equipped with a 200 MHz shielded antenna.
12
Figure 12 Surveying of the landing strip with the Nicaraguan metal detector
(VALLON model VMH3CS).
13
Figure 13 Area of the river mouth with the points of interest measured during
the two site visits plotted on an aerial photograph dated
22 January 2016, when the sand spit was largely diminished.
14
Figure 14 Initial research area established on the western side of
Los Portillos/Harbor Head Lagoon using the co-ordinates given by
Nicaragua for the marker found on 26 November 2003
(10° 56' 2.3"W, 83° 40' 24.4"N). The location of that point was
marked with a wooden stick (see arrow). The Nicaraguan operator of
the metal detector is standing next to the stick. In the foreground, the
GSSI GPR system of Costa Rica with a 400 MHz shielded antenna.
15
Figure 15 Piercing the sand with 2 m long iron rods. 15
Figure 16 Lowering the higher portion of the beach with shovels and piercing
systematically the sandy ground with 2 m long iron rods. The sticks
mark the investigated points, forming a grid with a spacing of around
0.4 m.
16
Figure 17 Map of Greytown Harbor (1899). The enlargement shows the
rectangular excavation at which co-ordinates were taken. The black
lines along the shore depict the path of the old railway.
18
Figure 18 Area of the lagoon with the points of interest measured during the
two site visits projected on a satellite image of 22 January 2016.
19
Figure 19 Annotated satellite image (Landsat, December 2016) showing the
main geographical-geomorphic features of the lower reaches of the
San Juan fluvial system associated with the Caribbean coast.
22
Figure 20 Effects of Hurricane Otto in the cemetery of Greytown. Image taken
during the first site visit on 6 December 2016 (twelve days after Otto
made landfall in the area).
24
Figure 21 Sketch illustrating the geomorphological-geographical units of the
analysed area relevant to the case.
24
Figure 22 Cartographic overlay of the coastline as represented in a historical
map produced by George Peacock in 1832 and updated in 1840, on a
satellite image taken on 5 October 2013. Note the retreat of the
coastline and the reduction of the extent of
Los Portillos/Harbor Head Lagoon (Figure 2 of the Statement from
March 2015 prepared by Prof. Colin Thorne in relation with the case
concerning Certain activities carried out by Nicaragua in the border
area Costa Rica v. Nicaragua).
25
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Figure 23 View of the relatively firm and stable land covered by coconut trees
that forms the eastern edge of Los Portillos/Harbor Head Lagoon. In
the background and to the left, the spit-barrier of
Los Portillos/Harbor Head Lagoon is visible. Image taken during the
second site visit on 15 March 2017.
25
Figure 24 Sand spit-barrier between Los Portillos/Harbor Head Lagoon (left)
and the Caribbean Sea (right). View looking to the west. Image
taken during the first site visit on 6 December 2016.
26
Figure 25 Sand spit-barrier between the Caribbean Sea (left) and
Los Portillos/Harbor Head Lagoon (right). View looking to the east.
Image taken during the first site visit on 5 December 2016.
27
Figure 26 Portions of the 1970 and 1988 editions of the 1:50,000 scale
topographic maps of Punta de Castilla (sheet 3448 I) of the Instituto
Geográfico Nacional de Costa Rica. The maps reveal that there used
to be in recent times a channel-like water gap connecting the
Los Portillos/Harbor Head Lagoon with the San Juan River. Note
that at that time the spit associated with the mouth of the San Juan
River was attached to Punta de Castilla, not to the western extremity
of Isla Portillos (see Figure 3 for comparison).
27
Figure 27 Point Ple located at the base of the sand spit-barrier of the
Los Portillos/Harbor Head Lagoon. This point is located at the
contact between the relatively stable surface covered by tree
vegetation on the eastern margin of the lagoon, and the accumulation
of loose sand that forms the spit-barrier. The GPS receiver of
Costa Rica is located at the base of a coconut tree. The flooded
coconut trees in the background reveal the high water level that
reached the lagoon after Hurricane Otto. Image taken during the first
site visit on 6 December 2016.
28
Figure 28 Point Plw measured during the first site visit at the western extremity
of Los Portillos/Harbor Head lagoon. The point was located at a
high-water mark defined by stranded vegetation indicating the
maximum level reached by the water of the lagoon after Hurricane
Otto. Image taken on 6 December 2016.
28
Figure 29 Channel breached in the beach of Isla Portillos, west of the
spit-barrier of Los Portillos/Harbor Head Lagoon. The water of the
lagoon was flowing towards the sea through this channel. The star
indicates the location of point Pch. Image captured from a video
recorded by the Nicaraguan delegation during the first site visit in
December 2016.
29
Figure 30 Topographer of the Costa Rican delegation measuring the eastern
bank of the channel through which the lagoon was draining towards
the sea (point Pch). On the other side of the channel the tree
vegetation is in direct contact with the sea waves. Image taken during
the first site visit on 6 December 2016.
29
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Figure 31 Channel opened in the beach of Isla Portillos, close to the western
extremity of the Los Portillos/Harbor Head Lagoon. The water of the
lagoon was flowing into the sea. Flow direction is towards the
camera. Image taken during the first site visit on 8 December 2016.
30
Figure 32 Image of Point Ple2, which represents the easternmost edge of the
water body of Los Portillos/Harbor Head Lagoon on its northeast
corner during the second site visit. The point was marked with a
wooden stick, being measured by a topographer from Nicaragua
(right). The monument to the right corresponds to a marker whose
designation (Δ and a reversed s as subscript, referred to by the Parties
as the “A2” Marker) has not been identified in the Proceedings of the
Costa Rica-Nicaragua Demarcation Commissions of the end of the
19th century. Image taken during the second site visit on 15 March
2017.
30
Figure 33 Point Plw2 (asterisk) measured during the second site visit at the
western extremity of the water body of
Los Portillos/Harbor Head Lagoon and general view of its sand
barrier. Image captured by the drone of the Costa Rican delegation
in March 2017.
31
Figure 34 Topographer of Costa Rica (left) measuring the co-ordinates of the
western extremity of the water body of
Los Portillos/Harbor Head Lagoon (covered by floating debris)
during the second site visit. Image taken on 15 March 2017.
31
Figure 35 Point Pleb (wooden stick) measured during the second site visit at
low tide (15 March 2017, at 8:57 a.m.). This point represents the
intersection between the shoreline and the projection of the
northeastern corner of the Los Portillos/Harbor Head Lagoon
perpendicular to the coast.
32
Figure 36 Position of the channel opened by Hurricane Otto (arrow). The
channel was closed during the second site visit due to the recovery of
the sandy beach. Image captured by the drone of the Costa Rican
delegation during the second site visit in March 2017.
32
Figure 37 Oblique aerial photograph of the spit-barrier of
Los Portillos/Harbor Head Lagoon showing a temporary inlet
channel. Image taken on 3 August 2012 (provided by Costa Rica on
20 October 2016).
33
Figure 38 Map of San Juan del Norte Bay produced by George Peacock in 1832
and updated in 1840. The San Juan River used to flow into an open
lagoon through multiple distributary channels forming a small delta,
which nowadays roughly corresponds to Isla Portillos, as defined in
this Report.
34
Figure 39 Image of the coastal stretch of Isla Portillos affected by severe
erosional retreat. Here, the mangrove forest is in direct contact with
the sea and affected by wave action. Image taken during the first site
34
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visit on 5 December 2016.
Figure 40 Coastal stretch of Isla Portillos, which was affected by severe
erosional retreat during the first site visit. This image, taken during
the second site visit, illustrates the considerable recovery of the beach
by sand accumulation related to wave action under regular
conditions.
35
Figure 41 Discontinuous and elongated lagoons between the beach and the
relatively stable area covered by dense vegetation of Isla Portillos.
Image captured from a video recorded by Nicaragua with a drone
during the first site visit in December 2016.
35
Figure 42 Oblique aerial view taken by the Costa Rican drone during the
second site visit in March 2017, showing the discontinuous lagoons
between the beach and the area covered by dense vegetation of
Isla Portillos. Note that the lagoons were much less extensive than
during the first site visit (see figure 41 for comparison).
36
Figure 43 Western sector of the coast of Isla Portillos, close to the mouth of the
San Juan River, where the lagoons or coastal lakes terminate before
the mouth of the San Juan River. Image captured from a video
recorded by Nicaragua with a drone during the first site visit in
December 2016.
36
Figure 44 Sequence of maps illustrating the main changes in the coastline
identified comparing satellite images from different dates (January
1970, December 2011, June 2013, April 2014). The satellite images
were retrieved from the historical imagery of GoogleEarth. Note the
substantial modifications experienced by the spit of Isla Portillos at
the mouth of the San Juan River (right bank).
37
Figure 45 The Nicaraguan delegation measuring the geographical co-ordinates
at the base of the sand spit of Isla Portillos (point Pv). Image taken
during the first site visit on 5 December 2016.
38
Figure 46 Image captured by the drone of the Nicaraguan delegation in
December 2016, showing the spit of Isla Portillos and the mouth of
the San Juan River on its eastern bank. The spit was most probably
diminished by erosion associated with the Hurricane Otto
(24 November 2016). The star indicates the location of point Pv.
38
Figure 47 Spit of Isla Portillos and the mouth of the San Juan River on its
eastern bank (arrow) during the second site visit. The spit
experienced a significant westward growth by sand accretion
between the first and the second visit (see Figure 46 for comparison).
Image captured by the drone of the Costa Rican delegation in March
2017.
39
Figure 48 Annotated satellite image from June 2013 (Digital Globe; U. S.
Geological Survey) indicating the approximate location of the
starting-points of the maritime boundary proposed by Costa Rica
42
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(CR) and Nicaragua (N).
Figure 49 Measurement of co-ordinates by Costa Rica (left) and Nicaragua
(right) of the point at which the right bank of the San Juan River
(Prmb) meets the sea at low tide (6 December 2016, at 11:25-11:27
a.m.).
43
Figure 50 Measurement of co-ordinates by Nicaragua (left) and Costa Rica
(right) of the point at which the right bank of the San Juan River
(Prm2) meets the sea at low tide (14 March 2017, at 8:16-8:17 a.m.).
43
Figure 51 Printed sketch-map attached to Alexander’s First Award. 45
Figure 52 Sketch included in Proceedings X of the Costa Rica-Nicaragua
Demarcation Commissions, showing the relative co-ordinates of the
Mojón Inicial (Initial Marker) with respect to the marker placed in
the center of Plaza Victoria.
47
Figure 53 Sketch of the San Juan River and Los Portillos/Harbor Head Lagoon
showing the first segment of the land boundary and the location of
the Initial Marker (Proceedings X of the Costa Rica-Nicaragua
Demarcation Commissions).
48
Figure 54 Triangulation measurements obtained in August 1899 between
Punta de Castilla (C), Initial Marker (I), Main Marker (A), and
auxiliary markers Am and A1. Note that Punta de Castilla is located
91.44 m to the NW (140º 52') of the Initial Marker (Proceedings XX
of the Costa Rica-Nicaragua Demarcation Commissions).
49
Figure 55 Sketch showing the geometrical features and parameters of the two
types of markers installed for facilitating the exact placement of
Punta de Castilla and the Initial Marker at any given time
(Proceedings XX of the Costa Rica-Nicaragua Demarcation
Commissions).
50
Figure 56 Marker found in the beach by the Sub-Commission on Limits and
Cartography on 21 February 2003 and on 25 November 2003. The
side exposed by the excavation was marked with a letter “A”
accompanied by another illegible symbol. This marker was
measured by both Parties for 2:50 hours with hand-held GPS devices.
52
Figure 57 Submerged marker found on 26 November 2003 in
Los Portillos/Harbor Head Lagoon. Co-ordinates were measured by
Nicaragua with a hand-held GPS.
52
Figure 58 Inscription on the western side of the monument located on the
eastern side of Los Portillos/Harbor Head Lagoon. Image taken
during the first site visit (7 December 2017).
54
Figure 59 Investigation by probing in an area around the point estimated for the
location of marker A1, assuming that the marker found in the beach in
2003 was marker Am and the average co-ordinates were the best
55
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approximation for its location. Image taken on 9 December 2016
during the first site visit.
Figure 60 Projection on a satellite image from 2003 of the co-ordinates
measured by Nicaragua and Costa Rica for the markers found in
2003 in the beach (square representing average co-ordinates and
triangles the measurements of the Parties) and submerged in the
lagoon (yellow circle).
55
Figure 61 GPR survey carried out in an area enclosing the co-ordinates
measured by Nicaragua for the marker found in 2003 submerged in
Los Portillos/Harbor Head Lagoon. A total of 12 GPR profiles 27 m
long were acquired with a spacing of 2 m. Pink flags indicate the
starting and end points of the profiles.
56
Figure 62 Partial view of the area investigated with GPR, metal detector and
iron rods around a point established with the co-ordinates measured
in 2003 by Nicaragua for the marker found submerged in the water.
The sticks driven into the sand, with a spacing of around 0.4 m, mark
the points investigated by probing with 2 m long iron rods.
Excavations were carried out at the location of the GPR and
metal-detector anomalies, as well as along the higher part of the
beach, in order to introduce the probes at a lower elevation and
increase the investigation depth.
57
Figure 63 Survey with the metal detector of Nicaragua of the selected 180 m
long portion of the airstrip at San Juan del Norte. Image taken during
the second site visit on 13 March 2017.
58
Figure 64 Prospecting for the marker of Plaza Victoria in the airstrip of the
San Juan del Norte airport with a GPR (Ground Penetrating Radar) of
the Nicaraguan delegation using a 200 MHz shielded antenna. The
vegetation in the northern flank of the airstrip was being cleared for
GPR and metal detector surveying. Image taken during the second
site visit on 13 March 2017.
58
Figure 65 Georeferenced Map of Greytown Harbor of 1899, produced by the
Nicaragua Canal Commission.
60
Figure 66 Georeferenced Map of Greytown of 1888 showing the center of Plaza
Victoria and the corners of the cemeteries measured with GPS by the
Parties.
60
Figure 67 Georeferenced Map of San Juan del Norte of 1966 produced by the
US Army, used as basemap for georeferencing the Map of Greytown
Harbor of 1899.
61
Figure 68 Georeferenced satellite image of 18 December 2009 acquired by
RapidEye sensor, used as basemap for georeferencing the Map of
Greytown Harbor of 1899.
61
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Figure 69 Ground Control Points used for georeferencing the Map of Greytown
Harbor of 1899 (top) using as basemaps the Map of San Juan del
Norte of 1966 (center) and a satellite image from 2009 (bottom).
62
Figure 70 Transparent overlay of the Map of Greytown Harbor of 1899 on the
Map of San Juan del Norte of 1966 with the corners of the cemeteries
measured by the Parties, depicting the estimated center of Plaza
Victoria.
63
Figure 71 Transparent overlay of the Map of Greytown Harbor of 1899 on the
Map of San Juan del Norte of 1966 showing the alignment of the
corners of the cemeteries measured by the Parties with a street
(enlargement of the previous figure).
63
Figure 72 Transparent overlay of the Map of Greytown Harbor of 1899 on the
satellite image of 2009 with the corners of the cemeteries measured
with GPS by the Parties, depicting the estimated center of Plaza
Victoria.
64
Figure 73 Transparent overlay of the Map of Greytown Harbor of 1899 on the
satellite image of 2009 showing the alignment of the corners of the
cemeteries measured with GPS by the Parties with the linear edge of
the high vegetation south of the landing strip (enlargement of the
previous figure).
64
Figure 74 Transparent overlay of the Map of Greytown Harbor of 1899 on the
aerial photograph of 1961 provided by Costa Rica, with the corners
of the cemeteries measured with GPS by the Parties, depicting the
estimated center of Plaza Victoria.
65
Figure 75 Map of Greytown of 1888 (top) and Map of Greytown Harbor of
1899 (bottom) indicating the 20 GCPs used for georeferencing the
1888 map and depicting the estimated location of the center of Plaza
Victoria.
66
Figure 76 Transparent overlay of the georeferenced Map of Greytown of 1888
on a georeferenced aerial photograph of 1961, with the corners of the
cemeteries measured by the Parties and the estimated center of Plaza
Victoria.
67
Figure 77 Transparent overlay of the georeferenced Map of Greytown of 1888
on a georeferenced aerial photograph of 1961, with the corners of the
cemeteries measured by the Parties and the estimated center of Plaza
Victoria (enlargement of the previous figure).
67
Figure 78 Transparent overlay of the georeferenced Map of Greytown of 1888
on the georeferenced satellite image of 2009 with the corners of the
cemeteries measured by the Parties and the estimated center of Plaza
Victoria.
68
Figure 79 Transparent overlay of the georeferenced Map of Greytown of 1888 68
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on the georeferenced satellite image of 2009 with the corners of the
cemeteries measured by the parties and the estimated center of Plaza
Victoria (enlargement of the previous figure).
Figure 80 Transparent overlay of the sketch of Proceedings X of the Costa
Rica-Nicaragua Demarcation Commissions (1897-1900) on the
satellite image of 2009. The overlay was produced using the coordinates
calculated for the center of Plaza Victoria and the
triangulation data included in Proceedings X.
69
Figure 81 Triangulation sketch included in Proceedings XX of the Costa Rica-
Nicaragua Demarcation Commissions (1897-1900) projected on a
Worldview image of 2016. I stands for Initial Marker and C for Punta
de Castilla.
70
Figure 82 Distances between the location estimated for the Initial Marker to the
closest land point on a satellite image from 22 January 2016 and
points Plw and Ple measured during the first site visit.
71
Figure 83 Distances between the location estimated for the Initial Marker to the
closest land point on a satellite image from 22 January 2016 and
points Plw2 and Ple2 measured during the second site visit.
71
Figure 84 Distances between the location estimated for Punta de Castilla to the
closest land point on a satellite image from 22 January 2016 and
points Plw and Ple measured during the first site visit.
72
Figure 85 Distances between the location estimated for Punta de Castilla to the
closest land point on a satellite image from 22 January 2016 and
points Plw2 and Ple2 measured during the second site visit.
72
Figure 86 Overlay of the georeferenced sketch of Proceedings X of the Costa
Rica-Nicaragua Demarcation Commissions from 1899 on a satellite
image acquired in 2009, showing a coastal retreat of around 940 m
on the eastern side of Los Portillos/Harbor Head Lagoon.
75
Figure 87 Satellite image from 2016 showing the position of the coastline
mapped with images from multiple dates (1940, 1961, 1981, 1987,
2002, 2009, 2016).
76
Figure 88 Hypothetical scenario considering a general 300 m retreat of the
coastline. The mouth of the San Juan River could shift around 1 km
to the east.
76
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LIST OF TABLES
Number Title Page
Table 1 Geographical co-ordinates measured by the topographical teams of
Nicaragua and Costa Rica during the site visits and used in this report
(WGS 1984 coordinate system).
40
Tables 2 Geographical co-ordinates (WGS 1984) of the point at which the
right bank of the San Juan River meets the sea at the low-water line,
measured during the two site visits by the topographical teams of
both Parties
42
Table 3 Satellite images provided by Digital Globe. 73
___________