This chapter evaluates flood inundation area in Fogera-Dera floodplain under future climate change in Lake Tana basin. Downscaling of the Global Climate Model (GCM) to watershed level was done by Linear Scaling (LS) bias correction method. Parameter-efficient semidistributed watershed (PED-W) model was used to simulate streamflow under baseline and future climate projections. Two-dimensional (2D) BASEMENT hydrodynamic model was used for flood inundation area evaluation. Calibration and validation of PED-W indicated very good agreement with R 22 =0.77 and NSE=0.76, respectively, on daily basis. Inundation area increased from 36.76 to 38.4, 41.91, and 46.36km2 in RCP 2.6 and 40.12, 44.15, and 48.21km2 in RCP 8.5 for 2020s, 2050s, and 2080s, respectively. Flooding in Dera-Fogera areas would be aggravated under future climate change. Flood monitoring and management systems have to be developed taking into consideration climate change scenarios.
