TITLE:
Dam Breach Analysis Using HEC-RAS and HEC-GeoRAS: The Case of Kesem Kebena Dam
AUTHORS:
Abimael Leoul, Nebiyou Kassahun
KEYWORDS:
Dam Breach Analysis, Flood Mapping, HEC-RAS, HEC-GeoRAS
JOURNAL NAME:
Open Journal of Modern Hydrology,
Vol.9 No.4,
October
11,
2019
ABSTRACT: Ethiopia has been booming with active construction of
dams within the past few decades for different infrastructural needs, but has
never experienced demolition or failure of dams in its history; hence little
attention is being given to possible breach scenarios of dams and the resulting
floodings. This paper makes analysis of the possible breach of kesem dam and
the resulting flood inundation. In this study, the dam has been checked for
both overtopping and piping failure modes using one dimensional river analysis
model called HEC-RAS. Empirical equations were used to predict dam breach
parameters of the two failure modes for use in this model. PMF inflow with a
peak 9237.77 m3/s is used as an input to the reservoir to check if
overtopping failure was possible. The spill way has proven to have adequate capacity
for the flood due to the PMF. Therefore, breaching of the embankment was not
possible. Piping failure was also simulated in HEC-RAS and the resulting breach
due to piping failure, was analyzed and flood hydrograph was obtained at
different cross sections along the river. These are flood hydrographs at 20 km,
40 km and 60 km at the downstream. The resulting flood plain was also mapped
using HEC-GeoRas to show the extent of flooding.