Extreme Weather and Flood Forecasting and Modelling for Eastern Tana Sub Basin, Upper Blue Nile Basin, Ethiopia

Abstract

River flood is a natural disaster that occurs each year in the Fogera floodplain causing enormous damage to the human life and property. Overflow of Ribb and Gummara rivers and backwater effects from Lake Tana has affected and displaced thousands of people since 2006. Heavy rainfall for a number of days in the upper stream part of the catchment caused the river to spill and to inundate the floodplain. Three models were used for this research; the numerical weather prediction model (WRF), physical based semi distributed hydrological model SWAT) and the LISFLOOD_FP 1D2D flood inundation hydrodynamic model to forecast the extreme weather, flood and flood modeling. Daily rainfall, maximum and minimum temperature for the forecasted period ranges from 0 to 95.8mm, 18 to 28oc and 9 to 18oc, respectively. The maximum forecasted flow at Ribb and Gummara rivers were to be 141m3/s and 185 m3/s, respectively. The flood extent of the forecasted period is 32km2; depth ranges 0.01 to 3.5m; and velocity ranges from 0 to 2. 375 m/s. This technique was shown to be an effective way of flood forecasting and modeling. Integrating Rainfall Runoff model with hydrodynamic model provides thus good alternative for forecasting and modeling.

Keywords: SWAT, LISFLOOD, WRF, Extreme weather, forecasting and modeling.