3 june 2002 aiacc v&a training workshop, trieste, 3-14 june 20021 v&a studies on coastal...
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3 june 2002 AIACC V&A Training Workshop, Trieste, 3-14 june 2002
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V&A Studies on coastal zones: the case of Senegal
Dr Isabelle NIANG-DIOPDepartment of Geology, Faculty of Science and
TechnologyUniversity Cheikh Anta Diop, Dakar (SENEGAL)
3 june 2002 AIACC V&A Training Workshop, Trieste, 3-14 june 2002
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The Senegal example
Two studies realized (1991 and 1999)
Conditions Results (for a sea level rise of 1 m
by 2100) What to deduce ?
3 june 2002 AIACC V&A Training Workshop, Trieste, 3-14 june 2002
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Conditions
First study Study in
collaboration with USA
All the Senegalese coastline
EPA funding (17,391 – 26,087 US$ )
10 months (may 90 – february 91)
Video recording (AVVA)
Second study Pluridisciplinary
team (11 experts) Case studies : Cap
Vert and Saloum Netherlands funding
(86,000 US$ ) 2 years (97-99) Remote sensing
and GIS
3 june 2002 AIACC V&A Training Workshop, Trieste, 3-14 june 2002
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Methodologies used The Common Methodology (IPCC, 1991),
basis for the IPCC methodology (Carter et al., 1994). The seven steps methodology
Based on scenarios Climate change scenarios
Sea level rise scenarios (used in the 2 studies) Inundation levels Other climate parameters (temperature,
precipitations,..) Socio-economic scenarios
Population growth Economic growth
3 june 2002 AIACC V&A Training Workshop, Trieste, 3-14 june 2002
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Sea level rise scenarios
Sr, t = Sg, t + So, t + V. t
avec Sr, t : relative sea level rise in t years
Sg, t : global mean sea level rise in t
So, t : regional changes in sea level due to oceanic circulation (currents, …)
V : earth movements (m/year) t : number of years considered
3 june 2002 AIACC V&A Training Workshop, Trieste, 3-14 june 2002
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Sea level rise with the SRES
See IPCC Third Assessment Report (2001)
3 june 2002 AIACC V&A Training Workshop, Trieste, 3-14 june 2002
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Inundation levels (Hoozemans et al., 1993)
D = MHW + Sf + Wf + Pf
MHW mean high water levelSf sea level rise
Wf heigth of storm waves of a givenreturn period
Pf rise in sea level due to barometric pressure
3 june 2002 AIACC V&A Training Workshop, Trieste, 3-14 june 2002
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Socio-economic scenario
the discount rate
Controversial question (utilitity, rate)
Multiplicator factorDt = 1 / (1 + r)t
Dt is discount factor in year t and r the discount rate used (2 to 7%)
3 june 2002 AIACC V&A Training Workshop, Trieste, 3-14 june 2002
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Scenarios generation Climate change scenarios
See the training workshop CC scenarios generators (MAGICC-
SCENGEN, regional CC models) Downscaling, national CC scenarios
Socio-economic scenarios National scenarios (to be preferred) United Nations and others scenarios (WB,
UNDP, WRI,…)
3 june 2002 AIACC V&A Training Workshop, Trieste, 3-14 june 2002
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Scenarios used First study
Climate change scenario Sea level rise by year 2100 : 0.2; 0.5; 1 and 2
m Inundation levels
2m1m
0.5m
No socio economic scenario
3 june 2002 AIACC V&A Training Workshop, Trieste, 3-14 june 2002
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Scenarios used Second study
Climate change scenario Sea level rise
2050 : 7, 20, 39 cm 2100 : 20, 49, 86 cm
Inundation levelsThe minimum inundation level by 2100 is calculated for minima values of themean high sea level, mean swell heights and the low estimation of sea level rise.The maximum inundation level considers mean values of the mean high sealevel, storm waves with a 1/100 return period and the high estimation of sea
level rise. Coast north of Dakar : 2 and 8 m Coast south of Dakar and Saloum : 2 and 6m
Other parameters Temperature rise : 1° and 1.9°C by 2050 Precipitation decrease : -1 to –10% in Cape Verde ; -1 to
–15% in Saloum
3 june 2002 AIACC V&A Training Workshop, Trieste, 3-14 june 2002
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Scenarios used Second study
Socio-economic scenario Population growth
Cap Vert : 2.99% Saloum : 2%
Agricultural production growth rateO.41%
Discount rates3 and 6%
3 june 2002 AIACC V&A Training Workshop, Trieste, 3-14 june 2002
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Impacts assessment Biophysical impacts
Land losses due to Coastal erosion Inundation
Salt water intrusion in coastal aquifers Coastal ecosystems Halieutic resources and fisheries
3 june 2002 AIACC V&A Training Workshop, Trieste, 3-14 june 2002
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Impacts assessment Socio-economic impacts
Population at risk Economic value at risk
Buildings Infrastructures Agricultural production
3 june 2002 AIACC V&A Training Workshop, Trieste, 3-14 june 2002
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Coastal erosion induced by SLR
The Bruun rule (1962)
A simple rule but based on a number of assumptions (equilibrium profile)
R = G L s (B + d)
R is the coastal retreat, L the width of the active profile, B the dune heigth, d the depth of closure, s the sea level rise and G a overfill ratio
3 june 2002 AIACC V&A Training Workshop, Trieste, 3-14 june 2002
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The Bruun rule (1962)
Bs
d
L
R
Profile translation
3 june 2002 AIACC V&A Training Workshop, Trieste, 3-14 june 2002
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Coastal inundationIn the second study Inundation levels considered as contour
levels. Digitalization of contour levels Satellite images transformed and land-
use maps Use of a GIS : combination of the two
types of information Generation of areas and types of
inundated coastal zones
3 june 2002 AIACC V&A Training Workshop, Trieste, 3-14 june 2002
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Other biophysical impacts (1)
Salt water intrusion in the coastal aquifers the Ghyben-Herzberg formula : determine the
depth and distance to the coast of the interface sea water / freshwater (see UNEP guidelines)
the FEFLOW model was calibrated and used to determine the evolution of the salt water intrusion in the Dakar aquifer (Faye et al., 2001)
Coastal ecosystems (expert judgement) « niayes » ecosystem : based on the comparison
with historical data Mangroves : analogue study
3 june 2002 AIACC V&A Training Workshop, Trieste, 3-14 june 2002
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Other biophysical impacts (2)
Halieutic resources (expert judgement) Marine resources
Diminution in the intensity of upwellings and surface waters warming
Modification in coastal habitats (mangroves) Estuarine resources
Increase of salinity Increase of the dynamics Disparition of mangroves
3 june 2002 AIACC V&A Training Workshop, Trieste, 3-14 june 2002
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Socio-economic impacts
First study Based on the video recording and
analysis of buildings Types of buildings with value attribution
economic value at risk Rate of occupancy : 1O people in 100
m2population at risk
3 june 2002 AIACC V&A Training Workshop, Trieste, 3-14 june 2002
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Socio-economic impacts Second study
Based on the analysis of inundated areas Population density by zones and growth rate
population at risk Density of inhabitants by house (7.5 in Dakar and
9.6 in the Saloum estuary) habitat at risk Capital and added value by hectare Industrial
value at risk (only for the Mbao industrial zones) Road lengths and types identified, value per km
and type applied road infrastructures at risk area of agricultural production multiplied by
yields and a growth rate agricultural production at risk
3 june 2002 AIACC V&A Training Workshop, Trieste, 3-14 june 2002
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Adaptation assessment
First study Two options considered:
Protection of important areas Total protection (coasts with10 inhabitant per
km2) Two types of protection options
Seawalls : unit costs For a 0.5 m SLR : 0.12 to 2 million US$ per km For a 1 m SLR : 0.33 to 2.30 million US$ per km
Beach nourishment : unit costs : 6 US$ per m3 plus costs of terminal groins
3 june 2002 AIACC V&A Training Workshop, Trieste, 3-14 june 2002
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Adaptation assessment
Second study Protection option
Coastal protection works (seawalls and groins)
Seawalls: 2.2 to 4.6 million US$ per km Dune fixation : unit costs per ha
Other types of measures
3 june 2002 AIACC V&A Training Workshop, Trieste, 3-14 june 2002
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Vulnerability assessmentvulnerability classes (Nicholls,
1995)Categories of impacts Vulnerability classes
Low Middle High Critical
Populations at risk (in % of total population) Economic value at risk (in % of GDP) Land losses (in % of total area) Loss of wetlands (in % of total area) Costs of protection/adaptation (in % of GDP)
< 1%
< 1%
< 3%
< 3%
< 0,05%
1 – 10%
1 – 3%
3 – 10%
3 – 10%
0,05–0,25%
10 – 50%
3 – 10%
10 – 30%
10 – 30%
0,25 - 1%
> 50%
> 10%
> 30%
> 30%
> 1%
3 june 2002 AIACC V&A Training Workshop, Trieste, 3-14 june 2002
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Results of the first study(for a 1 m SLR)
Land losses - Inundation - Erosion
5,987 km2
55 – 86 km2
Population at risk 112 000 –183 0001.4 – 2.3 % 1990
population
Economic value at risk 499 – 707 millions US$12 – 17 % PNB 1990
Protection costs (important zones)
255 – 845 millions US$
3 june 2002 AIACC V&A Training Workshop, Trieste, 3-14 june 2002
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Results of the second study(for a 1 m SLR)
Cap Vert(1597 km2)
Saloum(4309 km2)
Land losses - Inundation - Erosion
57 – 398 km2
2.9 – 4 km2
1,690 – 2,911 km2
0.8 – 4 km2
Population at risk (in 2100)
730,249 - 4,787,828
847,191 to 11,807,410
Economic value at risk (with a 3% DR)
4.4 – 29.7 milliards $
4 – 55.3 milliards $
Protection costs (with a 3% DR) 0,004 – 0,026 M$ 0.06 M$
3 june 2002 AIACC V&A Training Workshop, Trieste, 3-14 june 2002
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Comparison of the 2 studies(for a 1 m sea level rise)
1st study : Sénégal
2nd study: Saloum
Land losses by:InundationCoastal erosion
5,987 km2
55 – 86 km2
1,690 – 2,911 km2
0.8 – 4 km2
Population at risk
112,000 –183, 000 847,191 -11,807,410
Economic value at risk
0.5 – 0.7 milliard US$
4 – 55.3 milliards $
Protection costs 0.3 – 0.8 milliards$
0.06 milliard$
3 june 2002 AIACC V&A Training Workshop, Trieste, 3-14 june 2002
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Results of the second study
1. Other impacts
Lowering of piezometric levels and salinization of numerous coastal aquifers
Risks of disparition of the guinean vegetation typical together with apparition of halophyte species in the « niayes » and modifications of mangrove. The risks are less till a 0.5 m SLR
Diminution of the halieutic production and of landings. Changes in the species composition. Health problems, conflicts, employment
3 june 2002 AIACC V&A Training Workshop, Trieste, 3-14 june 2002
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Results of the second study 2. Other adaptation options
Need for ICZM Better management of coastal and
marine resources (water, halieutic and estuarine resources, ecosystems)
New institutional, legislative measures Promotion of technical measures
(recuperation of salted soils, creation of a CC research center)
No quantification of these measures
3 june 2002 AIACC V&A Training Workshop, Trieste, 3-14 june 2002
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The example of Sénégal : conclusions
Don’t expect to have more than you invest Big differences in the results depending on
the methods used specially for population and economic value at risk
Confirmation of the high vulnerability of the country (south coast and estuaries in particular)
Importance of monitoring, sustainable management of resources, …
But how to take these issues in the development agenda of the country?
3 june 2002 AIACC V&A Training Workshop, Trieste, 3-14 june 2002
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The example of Sénégal : conclusions
It is not finished! New scenarios, models are coming Still limitations in the studies : biophysical
impacts to be quantified, economic valuation of mangroves, consideration of other sectors
And how to take these adaptation options in the development agenda of the country?