Sea Level Rise and Storm surges: High Stakes for a Small Number of Developing Countries

Transcription

1 Sea Level Rise and Storm surges: High Stakes for a Small Number of Developing Countries Susmita Dasgupta Benoit Laplante Siobhan Murray David Wheeler DECEE The World Bank March, 2009

2 Objective of our Study Estimation of the potential impact of a large (1- in-100 year) storm surge by contemporary standard. Comparison of the above with intensification of storm surge expected in this century. In modeling future climate, we considered changes in sea level rise, geological uplift and subsidence along coastlines. Scope of the study: 84 coastal developing countries in 5 Regions. Impact/ Exposure Indicators: Affected territory, Population, GDP, Agricultural Land, Wetlands, Major Cities other Urban Areas.

3 Methodology Hydrologically conditioned elevation data set was used to identify inundation zones from alternative storm surge (wave height) scenarios. Storm surges were calculated following the method outlines by Nicholls (2008). A distance decay function of 0.3m per 1 km distance from coastline was used to estimate the wave height for each inland cell. Low elevation coastal zones were defined following McGranahan et al. (2007) A country surface for each vulnerability indicator (population, GDP, Urban extent, cropland, wetlands, major cities) were constructed. Indicator surfaces were overlaid with the inundation zones to determine the spatial Exposure of each vulnerability indicator under storm-surge conditions.

4 Details on Inundation Zones For elevation, hydrologically conditioned SRTM data was used. All 5 0 x 5 0 coastal tiles of 90m SRTM data was downloaded. Following Nicholls (2008), storm surges (wave heights) were calculated as follows: Current storm surge = S100 Future storm surge = S100 + SLR + (UPLIFT * 100 yr ) / SUB + S100* x where: S100 = 1-in-100-year surge height (m) SLR = sea-level rise (1 m) UPLIFT = continental uplift/subsidence in mm/yr SUB = 0.5 m (applies to deltas only) x = 0.1, or increase of 10%, applied only in coastal areas currently prone to cyclone/hurricane. -vector coastline masks were extracted from SRTM version 2; Coastal attributes: S100, DELTAID, UPLIFT were downloaded from the DIVA GIS database. Surge associated with current and future storms with the elevation values of inland pixels w.r.t a coastline was used to delineate potential inundation area.

5 Limitations of our Study Relative likelihoods of alternative storm surge scenarios have not been assessed. We restrict our analysis mostly to coastal segments where historical storm surges have been documented. Small islands are excluded from the analysis. Absence of a global database on shoreline protection has prevented us from incorporating the effect of existing protection measures. Impacts of storm surges have been assessed using existing population, socio-economic conditions and patterns of landuse.

6 Data Sources Dimension Dataset Name Unit Resolution Source(s) Coastline Elevation Watersheds Coastline Attributes Population SRTM v2 Surface Water Body Data Hydrosheds conditioned SRTM 90m DEM Hydrosheds Drainage Basins DIVA GIS database GRUMP 2005 (prerelease) gridded population dataset NASA km 2 90m e/hydrosheds/viewer.php km 2 GDP 2005 GDP Surface Million US$ Agricultural Land e/hydrosheds/viewer.php. Counts 1km CIESIN 1km Globcover 2.1 km 2 300m World Bank, obcover Urban Areas Grump, revised km 2 1km CIESIN Wetlands GLWD-3 km 2 1km Cities City Polygons with Population Time Series Urban Risk Index*, Henrike Brecht, 2007

7 Global Impacts Current Storm Surge Coastal Land Area (Total= 2,012,753 km 2 ) With Intensification Exposed area 391, ,255 % of total coastal area Coastal Population (Total= 707,891,627) Exposed population 122,066, ,073,563 % of total coastal population Coastal GDP (Total =1,375,030 million USD) Exposed GDP 268, ,794 % of total coastal GDP

8 Global Impacts (cont d) Current Storm Surge Coastal Urban Area (Total= 206,254 km 2 ) With Intensification Exposed area 40,189 55,180 % of total coastal Urban area Coastal Croplands (Total= 505,265 km 2 ) Exposed croplands 59,336 88,550 % of total coastal croplands Coastal Wetlands (Total = 663,930 km 2 ) Exposed area 152, ,508 % of total coastal Wetlands

9 Incremental Regional Impact (%) Land area Population GDP East Pacific Middle East North South Sub- Saharan Latin America Caribbean East Pacific Middle East North South Sub- Saharan Latin America Caribbean East Pacific Middle East North South Sub- Saharan Latin America Caribbean Extent of urbanization Wetlands Agricultural area East Pacific Middle East North South Sub- Saharan Latin America Caribbean East Pacific Middle East North South Sub- Saharan Latin America Caribbean East Pacific Middle East North South Sub- Latin Saharan America Caribbean

10 Top 8 Countries/Territories at Risk Rank Coastal Land Area Coastal Population Coastal GDP Coastal Cropland Coastal Urban Areas Coastal wetlands 1 Kuwait (81.1) Bahamas (73.0) Bahamas (65.7) Guyana (100.0) Bahamas (94.1) El Salvador (100.0) 2 Korea (61.7) Kuwait (70.0) Kuwait (65.3) UAE (100.0) Guyana (66.4) Belize (100.0) 3 Namibia (60.2) Djibouti (60.1) Belize (61.1) Nigeria (100.0) Djibouti (60.4) Kuwait (95.8) 4 Guinea (58.6) UAE (60.0) UAE (58.1) Qatar (85.7) UAE (60.2) Taiwan (95.2) 5 El Salvador (55.3) Belize (56.2) Mozambique (55.0) Korea (66.8) Togo (59.8) Namibia (81.6) 6 Chile (54.7) Yemen (55.7) Togo (54.5) El Salvador (66.7) Kuwait (56.4) Korea (78.8) 7 Bahamas (54.7) Togo (54.2) PuertoRico (52.7) Ghana (66.7) Yemen (55.4) Qatar (75.0) 8 PuertoRico (51.8) PuertoRico (53.8) Morocco (52.6) DPR Korea (58.3) Mozambique (55.1) Bahamas (71.4)

11 Major Cities at Risk Rank* EAP SAR AFR LAC MENA 1 Hai Phong (Vietnam) Barisal (Bangladesh) Bugama (Nigeria) Ciudad del Carmen (Mexico) Port Said (Egypt) 2 San Jose (Philippines) Mumbai (India) Okrika (Nigeria) Manzanillo (Cuba) Dubai (UAE) 3 Vung Tau (Vietnam) Cox s Bazar (Bangladesh) George (South ) Georgetown (Guyana) Rabat (Morocco) 4 Manila (Philippines) Khulna (Bangladesh) Quelimane (Mozambique) Bahia Blanca (Argentina) Kenitra (Morocco) 5 Roxas (Philippines) Bhaunagar (India) Mahajanga (Mozambique) Cienfuegos (Cuba) Aden (Yemen) * Indicator is percent of coastal area exposed.

12 Impact Zones and Likely Changes in Unprotected Shorelines Elevation (m) < > 40 Current storm surge Future storm surge SRTM current coastline New coastline Elevation (m) Less than one 1 2 More than 2 Elevation (m) < ,000 1,000 1,500 > 1,500 Current storm surge Future storm surge SRTM current coastline New coastline Elevation (m) Less than one 1 2 More than 2

13 Conclusions An increase in sea surface temperature is strongly evident at all latitudes and in all oceans. Scientific evidence to date indicates increased sea surface temperature will intensify cyclone activity and heighten storm surges. Millions of people in the developing world are likely to be exposed to inundation risk by sea level rise and storm surges within this century and accompanying economic and ecological damage will severe for many. Impacts are unevenly distributed across coastal countries with severe impacts limited to a few countries. A particularly striking finding is the concentration of highly-vulnerable large cities at the low end of the international income distribution.