Abstract:
Flood is the devastating natural events as it causes massive destructive of life, economy and infrastructure. The main objective
of this study was food inundation mapping using HEC-RAS model: the case of Awash Bello food plain, Upper Awash River
basin, Ethiopia. River geometry, annual peak food, and boundary conditions are the most important input parameters for
RAS preprocessing. The river cross-sections along the food plain were extracted using HEC-Geo RAS. Annual peak food
frequency analysis for diferent recurrence intervals (i.e., 2, 5, 10, 25, 50, and 100 years) was computed using the calibrated
and validated HEC-HMS model based on a 25 years (1990–2015) hydro-meteorological data collected from Ministry of
Water Resources Irrigation and Electricity and National Meteorological Agency, respectively. The model result depicted the
food extreme value for the respective recurrence interval was 526, 610, 828.8, 1072.8, 1263.6, and 1461.3 m3
/s, respectively.
For more reliability, the HEC-HMS model outputs were compared with the food extreme value obtained from Log Pearson
type-III, General Pareto and Gumbel extreme value distribution function and it was found the HEC-HMS model result for
every recurrence interval was higher than the extreme value distribution function outputs. After verifying the acceptability
of the HEC-HMS model result, the verifed peak food was inserted into HEC-RAS model and food inundation mapping
for diferent recurrence intervals were executed. The HEC-RAS model outcome indicated that the food inundation mapping
area for 2, 5, 10, 25, 50, and 100-year recurrence intervals, respectively, was 71.475, 76.630, 89.150, 100.290, 105.160, and
109.462 km2
. Finally, it was realized that the whole Awash Bello food plain is under the infuence of food inundation due
to the intensive rainfall event.
