How vulnerable is the Lower Niger Delta to inundation from Sea Level Rise? ZAHRAH N. MUSA, IOANA POPESCU, ARTHUR MYNETT UNESCO-IHE, Institute for Water Education Delft, The Netherlands 1

Focus on coastal areas 2 44% of world's population lives –UN within 150 km of the coast o high coastal population growth o high economic productivity o economic hubs of their countries (e.g. Rotterdam, Mumbai, Lagos, Guangzhou, etc)  Low elevation  Gentle slopes

Focus on coastal areas 3 Climate change o Rise in atmospheric temperature o Rise in sea surface temperature Consequences of climate change o Global warming o Change in precipitation patterns Increase/decrease o Increased frequency of floods o Rise in sea levels Increased frequency of storm surges Cyclones Flooding Intrusion of sea salts Inundation

Focus on coastal areas 4 o Loss of dry land o Loss of wetlands o Conversion of fresh water regimes to salt water regimes o Loss of natural biodiversity o creates a need for adaptation Dry land becomes a wetland, swamp or a part of a river, ocean /sea. Inundation from SLR  impeding drainage of river flood waters  inland movement of the shoreline  uplifting the groundwater table

The lower Niger delta 5  Area ~ 20,000 Km 2  450 km of coastline  Made up of nine states in the southern part of Nigeria  Nigeria’s economic hub  rich in oil and gas  main source of foreign exchange

The lower Niger delta 6 Environmental problems Natural o River flooding (Niger, Imo, Qua Iboe) o Erosion due to river and coastal flooding o Subsidence Man-made o Wood logging o deforestation o Oil spills o land loss o Contamination of surface water o Acid rain from gas flaring o corrodes roofing sheets o destroys biodiversity o Subsidence from oil and gas extraction

The Lower Niger Delta 7 Hydrology: Rivers, Creeks, Lakes, Estuaries

Physical properties Low elevation Gentle slope Subsiding due to oil and gas exploration estimated at mm/yr The Lower Niger Delta 8

9 Vulnerability to inundation Method: Modified Bath Tub approach using GIS to map inundation from sea level rise  SRTM DEM  NigeriaSat1 image  tidal surface  projected SLR values Rahmstorf predicted values Tidal surface: the longitude, latitude and water levels of 15 tide gauges located in the Niger delta. o Interpolate a raster

Vulnerability to inundation 10 SLR inundation process Total surface area = 23,623.4 km 2 Subset from NigeriaSat 1 image SLR values 2030 = 0.12 m m 2050 = 0.23 m m Tidal surface+ SLR = new water level New water level – SRTM value = inundated area

Vulnerability to inundation 11 SLR only inundation extents 0.12 m by 2030 = km 2 = 2.3% of the total surface area m by 2030 = km 2 = 2.6% of the total surface area.

Vulnerability to inundation 12 SLR only inundation extents 0.23 m by 2050= km 2 = 2.4% of the total surface area m by 2050= km 2 = 3.2% of the total surface area.

Vulnerability to inundation 13 SLR plus Subsidence inundation extents Land subsidence value = 25 mm/yr 2030 =0.75 m, and 2050= 1.25 m Land subsidence value +SLR + surface grid = new water level New water level – SRTM = inundated area

Vulnerability to inundation 14 SLR plus Subsidence inundation extents SLR (0.12 m ) + subsidence (0.75 m ) by 2030 inundation extent = km 2 = 3.4% of the total surface area. SLR (0.41 m ) + subsidence (0.75 m ) by 2030, inundation extent = km 2 4.6% of the total surface area.

Vulnerability to inundation 15 SLR plus Subsidence inundation extents SLR (0.23 m ) + subsidence (1.25 m ) by 2050 inundation extent = 1,511 km 2 = 6.4% of the total surface area. SLR (0.65 m ) + subsidence (1.25 m ) by 2050 inundation extent =1,759.5 km 2 = 7.5% of the total surface area.

Vulnerability to inundation to 3.2% of the Niger delta could be inundated due to SLR by to 7.5% of the Niger delta could be inundated due to SLR and land subsidence by Places affected… Implication

Vulnerability to inundation 17 Places affected….

Vulnerability to inundation 18 Population density…

Conclusion 19  The Niger delta is vulnerable to inundation by SLR o 2.3 to 3.2% could be inundated due to SLR by  Land subsidence will exacerbate the inundation effect of SLR on inland areas o 3.4 to 7.5% could be inundated due to SLR + land subsidence by  Based on projected population census data, 460,000 to 2.4 million people could be affected by SLR by the year 2050.

Thank you 20