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Carlos Drews & Ana Fonseca
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Produced by Communications Department
WWF Central America
2009
Graphic Design:
Jeffrey Muoz
Production:
Zeidy HidalgoMarianne Fish
Carlos Drews
Ana Fonseca
Edition:
Carlos Drews
Ana Fonseca
Translation:
Lucinda Taft
Cover Photo:Aerial photograph of Playa Grande, Las Baulas National Park, taken on May 1st, 2009 .
Carlos DREWS / WWF
Cite as:
Fonseca, A. & C. Drews. 2009. Rising sea level due to climate change at Playa Grande,
Las Baulas National Park, Costa Rica: inundation simulation based on a high resolution, digital elevation model and
implications for park management. WWF / Stereocarto Report, San Jos, pp. 20.
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Summary
Flooding models under dierent sea-level rise
scenarios are needed to better plan or coastal
development and protected areas, in a way such
that both marine turtles and local communities
beneft. Playa Grande, the most important nest-
ing site o the Eastern Pacifc or the critically
endangered leatherback turtle, is located in Las
Baulas National Park, Costa Rica. It is realisticto expect a 1 m sea-level rise by the end o
the century due to climate change. This would
imply a 50 m retreat o the beach landwards.
Additionally, the high-resolution, digital eleva-
tion model reveals that or the most part the
inundation o the Playa Grande area will occur
rom behind. As sea level rises, the water will
advance through the mouth o the Tamarindo
estuary, and into the surrounding wetlands, in-
undating part o the land bordering the current
mangroves. The uture o Playa Grande depends
on its ability to retreat as sea level rises and
at the same time maintain adequate ecological
conditions or the nesting o leatherbacks. This
implies that existing and uture inrastructure
does not hinder the retreat o the beach and that
the buer zone o the national park warrants e-
ective environmental mitigation measures in
the light o the uture locations o the beach
and o the retreat o the mangroves. The law
proposal to rectiy the boundaries o the park
that would reduce its width to a ringe o 50 m
would imply that the park would be underwater
by the end o the century. The beach would be
located inside the proposed wildlie reuge and
turtles and their nests would compete or space
with houses and other inrastructure. Once the
beach retreats against the inrastructure, the
wave action against roads and buildings will
cause erosion and, consequently, loss o nest-
ing area. In relation to rising sea levels, the pro-
posal to rectiy the boundaries o the national
park is shortsighted and not precautionary. It
would compromise in the mid- and long-term
its ecological role as leatherback nesting area,
and as such, the very reason or the creation o
this particular park. Implementation o adapta-
tion measures to counter the impacts o climatechange in turtle nesting beaches is an interna-
tional commitment under the Inter-American
Convention or Marine Turtle Protection and
Conservation, to which Costa Rica is a signatory
party. With the implementation o such mea-
sures, Costa Rica has the opportunity to main-
tain its regional leadership in the conservation
o marine turtles and its status as a world-class
reerence in biodiversity conservation.
Inundation simulation based on a high
resolution, digital elevation model and
implications for park management
Carlos Drews and Ana Fonseca
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Results and discussion
Simulation o the inundation o Playa Grande
One important preliminary step toward the denition
o adaptation measures or sea level rise and globa
warming due to climate change are accurate loca
inundation models that take the greatest number o
atmospheric, terrestrial and oceanographic variables
into account. Inundation modeling is a complex process that involves several analytical stages o the
marine-coastal and atmospheric dynamic. As a rs
stage, a digital land model was generated using LI-
DAR technology, an aerial sensor that scanned the
beach with laser beams, yielding high-resolution data
on topographical elevation. A possible inundation was
simulated statically based on this topography, ortho
photography and dierent sea level rise scenarios (0
to 150 cm)8. These simulations, images and maps are
useul tools or raising awareness and helping gov
ernmental and civil society decision makers plan the
incorporation o sea level rise into protected area and
coastal development management. The next stage o
this project will gather and add data on wave action
tides, bathymetry, currents, tectonics, precipitation
temperature, and more to the topographic data, to
analyze a wide range o vulnerabilities and generate
a more accurate, dynamic model o beach movemen
and inundation due to the impact o climate change
on these beaches.
According to the most recent estimates o a one-meter sea-
level rise anticipated or the end o the century, the beach
at Playa Grande will retreat some 50 meters during this
period 9, as the beach is pushed landwards by wave actio
as the sea level rises. Under this assumption, Figure 9 rep
resents the landward displacement o the beach, relative to
the current tide line. The public zone o 50 meters and the
maritime-terrestrial zone will gradually shit landwards too
I there were buildings in this zone, in the uture nesting
turtles would compete directly or space with houses and
other inrastructure as the beach shited to surround those
buildings. In theory, this could turn out to be the case with
regards to some o the buildings now in existence (Fig. 10)
although it is unknown whether the nesting zone preerred
by the leatherbacks will include these specic stretches o
8 Modications to the littoral zone during the periodcontemplated in the simulation are not illustrated. This
simulation is also known as a bathtub model o sea leve
rise. It does not take the retreat o the beach as sea leve
rises into account.
9 Source: Daz-Andrade, J.M. 1996,Anlisis de la
vulnerabilidad de la zona costera ante el ascenso de
nivel del mar por un cambio climtico global Costa
del Pacfco de Costa Rica, Inorme fnal del Proyecto
Centroamericano sobre Cambio Climtico, Comit Re
gional de Recursos Hidrulicos. San Jos, Costa Rica
ever, we also discuss the management implications o
projections or beach retreat based on published ac-
counts by other authors. A subsequent stage is expect-
ed to generate a dynamic model o the inundation that
also considers bathymetry, wave action and the littoral
zones response in shape and size. The latter will allow
calculation o eventual reorientations o the beach in the
uture and the range o extreme storm surges.
Methodology
Playa Grande beach is approximately 4.3 km long with
white sand, located in Guanacaste province. Its geo-
graphic coordinates are: northern end 10 20 44 N,
85 51 37 W and southern end 10 18 30 N, 85
50 11 W. The beach is protected within Las Baulas
Marine Park that also includes Ventanas, Langosta and
Carbn beaches, the San Francisco and Tamarindo es-
tuaries, and 125 m landward rom the regular high tide
line. Leatherbacks nest mainly in the center o the beach
where there is very little inrastructure at present.
On June 6, 2009, a fy-over o Playa Grande and Junquil-
lal Beach was done in a Piper Azteca PA-23-250 aircrat,
equipped or fights with simultaneous LIDAR and digital
photography technology. Flight hours or Playa Grande
were 08:04 to 08:16 am and or Junquillal rom 08:21 to
08:28 am, which determines the tide level shown in the
photographs. At the time o the overfight on that day, low
tide was at 7.35 h (46 cm) and high tide was at 13.52 h
(265 cm) in Puntarenas as a point o reerence. Thus, the
photographs portray low tide conditions. During the fight
laser data were captured with a LIDAR Leica ALS 50 II
sensor or generating the Digital Terrain Models (DTM,
see Fig. 4) and Digital Surace Models (DSM) rom the
lowest low tide point to 500 m landward, with a resolution
o 4 to 5 points/meter2 and an altitudinal precision o 15
cm. Additionally, aerial photos were taken on a 1:30,000
scale with a medium ormat RCD 105 digital camera that
were then ortho-rectied (Figs. 3, 5-10). The images
were integrated into a tridimensional vision system called
Stereocaptor to produce animations7 o the possible in-
undation o Playa Grande under dierent sea level rise
scenarios (rom 0 to 150 cm, every 10 cm).
The anticipated 50-m retreat o the beach landward has
not been refected in the simulations o simple inunda-tions. In order to illustrate this retreat, the orthophoto-
graph o the uture scenario in Figure 8 was edited us-
ing Adobe Photoshop, moving the beach landward and
maintaining current building locations as points o reer-
ence. In Figures 9 and 10, lines are used to indicate the
modied boundaries o the beach as a consequence o
their eventual uture displacement.
7 These animations are not included in this report
and are distributed by WWF upon request.
sures. This report graphically presents the results o
simple models to simulate inundation due to sea level
rise at Playa Grande and it mentions the implications
o the expected landward retreat o the beach or the
management o the national park.
Purpose and scope o this study
Massive hotel development and the parceling o real
estate or condominiums are exerting major ecosys-tem pressures in Guanacaste province that are most
intensive on the coastal-marine environments, where
aquiers, wetlands and mangroves are being aected.
The main challenge at Playa Grande is to achieve en-
vironmental compatibility o present and uture coastal
development with the ecological unction o the national
park. Some properties are still held within the park
boundaries and the government as per the correspond-
ing legal ruling should expropriate these. A drat law
has been submitted by the Presidency o the Republic
or the consideration o the Legislative Assembly that
proposes a reduction in the width o the park in order
to exclude these properties rom the area o maximum
protection and avoid the extensive costs o the expro-
priation. WWF has expressed its opposition to this drat
law based on considerations o the implications o sea
level rise, arguments that up until now did not gure
in the debate. Furthermore, a technical document rom
SETENA is in preparation about the park buer zone
(500 m wide, see Fig. 9) that will recommend mitiga-
tion measures or the environmental impact on the park
o development. Construction permits have been para-
lyzed in this zone until the Constitutional Court makes a
ruling on SETENAs recommendations. Consideration o
sea level rise is pertinent in these processes because
this will determine the location and condition o the
beach in the medium and long term.
The purpose o this study is to generate inundation
simulations or some scenarios o sea level rise due to
climate change, which can be used to raise awareness
in coastal communities about this problem and aid the
management authorities o protected wildlands in de-
signing inrastructure-ree setbacks that will allow Las
Baulas National Park to ulll its ecological unction in
the long term. We made a tridimensional, high-reso-
lution digital land model o Playa Grande using LIDAR
technology6
. At this stage the study has been limited togenerating a simple bath tub fooding simulation or
the sea level rise projected or the end o the century,
based on detailed topography o the littoral zone. How-
6 LIDAR (Light Intensity Detection and Ranging):
This is an active laser system that works in the visible,
ultraviolet and near inrared spectrum. It has applica-
tions in studies o the atmosphere and as an altimeter
in overfights that generate very accurate digital eleva-
tion models.
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a periodic record should be made o the distance
rom several points on the beach to xed points on the
coast, such as buildings and boundary markers These
records are necessary or designing the inclusion o set-
backs (zones behind the beach with no inrastructure
in land-use regulatory plans as an adaptation measure
to sea level rise. Las Baulas National Park has still not
designed the setbacks that are technically necessary to
compensate or sea level rise, such that the beach can
retreat landward and continue exercising its unction asthe most important nesting site o the Eastern Pacic o
leatherbacks, a critically endangered species.
The setback zone is essential to maintain the integri
ty o the coastal vegetation strip, which will also shi
arther inland; the vegetation unctions as a natura
barrier or mitigating the eects o articial lighting
rom buildings that disorients the turtles, and also
provides shade that can reduce the probability o
nest overheating13. Furthermore, prudent setbacks
must also be established to allow the gradual retrea
o this parks mangroves without harming their eco
logical unction. National parks should be designed
to ull their protective unction long-term. WWF is
preparing to work in coordination with SINAC and the
authorities o Las Baulas precisely to address this
challenge.
International commitment to adaptation to
climate change
In April 2009, during the 4th Conerence o the Par
ties to the Inter-American Convention or the Protec
tion and Conservation o Sea Turtles held in San Jos
the government o Costa Rica (a signatory nation
proposed resolution CIT-COP4-2009-R5 Adaptatio
o sea turtle habitats to climate change, which was
approved by consensus. This trailblazing resolution
urges signatory nations to design, identiy and imple
ment stronger corrective measures and adaptations
to climate change in management plans, regulatory
plans, and programs or the protection and conserva
tion o sea turtles and their habitats, among others
The implementation o corrective and adaptation mea
sures is an international commitment, in which Costa
Rica is already showing clear leadership with regard to
sea turtles, as demonstrated by the conservation proj
ect at Junquillal Beach where adjustments in management are now being implemented on the beach to
mitigate the impacts o climate change. This kind o
initiative is pending or Las Baulas National Park and
the other Costa Rican nesting beaches o regional and
global importance.
13 Measurements made by WWF at Junquillal Beac
indicate that the coastal vegetation strip can reduce in
cubation temperature by 2-3 degrees Centigrade along
the higher elevation stretch o the beach.
ta Rica, spring tides can reach up to 1 m above the level
o ordinary high tides12. This preliminary fooding simula-
tion does not refect that a 1-meter sea level rise by the
end o the century, considered realistic by the scientic
community, would probably also completely inundate the
50-meter strip o the current public zone. Figure 8 re-
constructs the eventual location o the beach by the end
o the century, displaced some 50 m landward, and it
illustrates how some buildings would be immersed on the
beach (also see Figs. 9 and 10). The estimated 50-me-ter retreat o the beach by the end o the century due to
sea level rise means that the current public zone will be
totally submerged by that time (Fig. 9). The drat law or
rectiying the boundaries o Las Baulas National Park11
(in review by the Permanent Special Commission or the
Environment o the Legislative Assembly) would reduce
the park to this 50-meter strip, condemning it to be under
water in the uture and, thus, to disappear by the end
o the century. In addition will be completely within the
proposed wildlie reuge, in immediate confict or space
with buildings and other inrastructure. Under these con-
ditions, the ecological unction o the beach as a leather-
back-nesting site would be seriously compromised.
Figures 8, 9 and 10 are approximations o the possi-
ble impact o the retreat o the beach due to sea level
rise but this estimate could be made more accurate in
a one-to-two year investigation o Las Baulas National
Park10 that would consider the evolution o wave ac-
tion, winds, tides and the topography under climate
change scenarios in a way that would also refect the
intrusion o peak high tides, to generate a dynamic in-
undation model with probability levels or normal and
extreme events. Inrastructure-ree setbacks must be
designed to reduce the vulnerability o the investments
in coastal development to the fooding due to rising
sea level and so as not to block the ormation o new
beach inland, thus maintaining conditions suitable or
nesting sea turtles. Such setbacks are a undamental
tool in sea turtle conservation, particularly in the con-
text o adaptation to climate change12.
Inrastructure-ree setbacks to compensate
or sea level rise
The Manual sobre tcnicas de manejo y conservacin
de las tortugas marinas en playas de anidacin de Cen-
troamrica, published in 2008 by the Inter-AmericanConvention or the Protection and Conservation o Sea
Turtles, o which Costa Rica is a member, indicates that
11 Expediente No. 17.383, Recticacin de Lmites
del Parque Nacional Marino Las Baulas y Creacin del
Reugio de Vida Silvestre Las Baulas de Propiedad Mixta
12 Fish M.R., I.M. Ct, J.A. Horrocks, B. Mulligan, A.R.
Watkinson and A.P. Jones. 2008. Construction setback
regulations and sea-level rise: mitigating sea turtle nesting
beach loss. Ocean and Coastal Management 51:330-341.
the beach in the uture. However, once the beach reaches
the inrastructure, wave action on roads and/or buildings
will cause erosion and loss o beach area. In Bonaire, or
example, it is estimated that 32% o the beach area will be
lost with a sea level rise o 50 cm, due to the inrastruc-
ture and natural obstacles that would impede the gradual
retreat o the beach10. It is essential that the current size
o Las Baulas National Park is maintained and buer zone
measures are dened to compensate or beach displace-
ment so that the park best ullls its ecological unction inthe short as well as the long term.
According to the preliminary simulation or a 1-meter
sea level rise, it is very probable that a large part o the
inundation o the Playa Grande zone would occur rom
behind, as sea level rises and water advances via the
mouth o the Tamarindo estuary and the surrounding
wetlands, fooding some lands adjacent to the current
mangrove area (Figs. 1, 2, 5 and 6). The small estuary
zone o Ventanas Beach will be signicantly inundated,
making the road parallel to the beach and the buildings
in this sector highly vulnerable (Figs. 7 and 10).
A quantitative assessment o the current tectonic ten-
dency in the area is still pending, in order to estimate
the component o sea-level rise due to the subsidence
o the continental platorm. The west coast o the Nicoya
peninsula, on which Playa Grande is located, is subsid-
ing. Observations in Junquillal beach suggest, that in
act, the mean sea level is rising along this stretch o
the coast. It is evident that the ocial landmarks o the
public zone need to be relocated inland, since their dis-
tance to the ordinary high tide line is noticeably less
than 50 meters. The tendency o the relative sea level
in Puntarenas or the period 1941-1978 is a net rise,
with a total increment o 51 mm over that period . The
current high tide level (usually drawn and dened as the
boundary between the maritime and terrestrial domains
or cartographic and legal purposes) is inundated ap-
proximately 8% o the time. However, i average sea
level rises by 1 m, this value increases to 51%, which is
the percentage o inundated time currently correspond-
ing to the mean tide level (mean between the average
low and the average high tide). Unortunately, there is
lack o data series or changes in sea level along the
Pacic littoral o Costa Rica, which have the continuity
and duration needed to estimate with more precision
these tendencies or several locations along the coast(A. Gutirrez, personal communication).
Sea level rise is a gradual process. Extreme tidal action
will increasingly reach those areas that today seem sae
rom inundation. Along the northern Pacic coast o Cos-
10 Fish, M.R., I.M. Cote, J.A. Gill, A.P. Jones, S.
Rensho and A.R. Watkinson. 2005. Predicting the
impact o sea-level rise on Caribbean sea turtle nest-
ing habitat. Conservation Biology 19:482-91.
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Figure 1. Inclined orthophotograph o Playa Grande
illustrating the inundation area corresponding to a 1-meter
sea level rise, probable by the end o the century.
Figure 2.DTM image o Playa Grande topographyillustrating dierences in elevation details in relie with
15-cm vertical resolution and the inundation area
corresponding to 50-cm and 100-cm sea level rises.
Conclusion
Flooding models are needed or dierent sea level rise
scenarios in order to better plan or coastal develop-
ment, in a way that would benet both sea turtles and
local residents. This project aims to contribute case
studies to enhance knowledge o the coastal process-
es associated with climate change on beaches o the
tropical Eastern Pacic that will allow better manage-
ment o the challenges o erosion, territorial manage-ment, conservation o marine-coastal biodiversity and
responsible development. The uture o Playa Grande
beach depends on its capacity to retreat rom rising
sea levels while maintaining ideal ecological condi-
tions or leatherback nesting. This implies that existing
and uture inrastructure must not block this retreat
and that the buer zone o the national park ensures
eective environmental mitigation measures or the
uture landward location o the beach. Due to the ore-
cast retreat o the beach, a rectication o the park
boundaries that would reduce its current width and
allow continued development o inrastructure withinthe 125-meter strip above the current regular high
tide level is neither a precautionary nor a preventa-
tive measure and it would compromise in the medium
and long term its ecological unction as a leatherbac
nesting site, the very reason or which this protected
area was declared. The implementation o adaptatio
measures or climate change on nesting beaches is
an international commitment under the Inter-Ameri
can Convention or the Protection and Conservation o
Sea Turtles, to which Costa Rica is a signatory party
In implementing such measures, Costa Rica has the
opportunity to maintain its regional leadership in seaturtle conservation and as a global reerence in biodi
versity conservation.
Figures
Year 2009
Year 2009 + 50 cm + 100 cm
+ 100 cm
Source:WWF/Stereocarto
So
urce:WWF/Stereocarto
Source: WWF / Stereocarto
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Figure 3. Inclined orthophotograph o Playa Grande, taken
on June 6, 2009.
Figure 4. DTM image o Playa Grande topography
illustrating details o dierences in elevation in relie with
15-cm vertical resolution. Note the low elevation o the
mangrove zone around the Tamarindo estuary and the
estuary behind Ventanas Beach. The beach dune stands
out with an elevation a little higher than the landward
terrain behind it.
Source:WWF/Stereocarto
Source:W
WF/Stereocarto
Actual sea level
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Figure 5. Comparison o vertical image orthophotographs o the eastern sector o Playa Grande illustrating current
sea level (above) and the inundation area with a 100-cm sea level rise, estimated or the end o the century. This
image does not include the expected 50-m displacement o the beach landward (see Fig. 9).
Source:WWF/
Stereocarto
Source:WWF/Stereocarto
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Figure 7. Comparison o vertical image orthophotographs o Ventanas Beach, western sector o Playa Grande, illustrating current sea level (above) and the inundation area
with a 100-cm sea level rise, estimated or the end o the century (below). This image does not include the expected 50-m displacement o the beach landward (see Fig. 10).
Source:WWF/Stereocarto
Source:WWF/Stereocarto
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Figure 8. Comparison o vertical orthophotographs o Playa Grande illustrating current sea level (above) and a 100-cm sea level rise, estimated or the end o the
century (below). This image recreates the expected 50-m displacement o the beach landward in response to sea level rise. Some buildings would end up on the
beach, subject to the impact o storm surges. Note that the road parallel to Ventanas Beach is highly vulnerable to eventual erosion, as it is situated on a narrow
sand bank, lanked by water on both sides and exposed to the beating o the waves and storm surges (let side o the image).
Source:WWF/Stereocarto
Source:WWF/Ste
reocarto
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Figure 9. Vertical orthophotograph o Playa Grande, illustrating areas o Las Baulas National Park in this sector, as well as the expected landward
displacement zone o the beach o 50 m in response to sea level rise, estimated using the Bruun rule (see the text).
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Figure 10. Vertical orthophotograph o Playa Grande and Ventanas Beach, illustrating areas o Las Baulas National Park in the northwestern sector, as
well as the expected landward displacement zone o the beach o 50 m in response to sea level rise, estimated using the Bruun rule (see the text).
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