Vulnerability of the Nile Delta to Recent and Future Climate Change

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Yasser Eldeberky, Birgit Hünicke

Tuesday 30 june 2015

17:15 - 17:30h at South America (level 0)

Themes: (T) Flood risk management and adaptation, (ST) Flood risk assessment

Parallel session: 7J. Floodrisk - Assessment

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The impacts of natural risks on low-lying coastal areas receive increased attention worldwide. The Fifth Assessment Report (AR5) of the Intergovernmental Panel on Climate Change (IPCC, 2014) indicated that global sea-level will continue to rise at a rate very likely to exceed the rate of the past four decades. Rising sea level could submerge some low-lying coastal plains; intensify wave action in the near-shore areas; and cause shoreline retreat. In addition to expected inundation events, wind storms may cause surges in coastal areas. Storm surges represent a major natural hazard in coastal zones in terms of wave run-up and over-topping. Thus, reducing natural risks in coastal lowlands is of utmost importance in coastal management under the current and future climate change. This paper presents observations and simulation of surge levels in the Mediterranean offshore the delta. The TRIM-NP model, which is based on Cartesian coordinates, has been applied to hindcast hourly water-levels throughout the region for 63 years from 1948 to 2011. The Mediterranean is modeled as a closed basin without water exchange with neighboring seas and water outflow from the river Nile. The spatial grid has been configured with a 5 km resolution, including 760 by 360 grid points. The temporal resolution of the simulation is 4 minutes. These spatial and temporal resolutions are adequate to capture the occurrence of highest water-levels in the region. This high-resolution hindcast represents an added value when compared to the previous simulation of the HIPOCAS project. The model was driven by wind fields and atmospheric pressure generated by the climate model CLM (with spectral nudging) for the Mediterranean region provided by coastDat (a model based regional meteorological reanalysis generated at the Helmholtz-Zentrum Geesthacht, Germany). Simulation of surge levels offshore the Nile delta during a recent severe storm indicated a surge value of 1 m similar to the value observed during the storm on December 11th, 2010. This surge level is relatively high compared to the typical surge (0.5 m) observed previously offshore the delta. The potential implications of rising sea-level on the Nile delta coast would be manageable if adaptation measures are established such as institutional coastal monitoring capabilities and imposing laws and regulations.