Abstract:
Through out the human history floods have been an integral part of the civilization. Still,
men have not quite coped well to live with floods. Flooding is the most frequent global
natural disaster; rural areas are becoming more vulnerable to flooding due to effect of
climate change. Flash flood is one of the most prominent phenomena caused by heavy
rains. In developing countries drainage channels is the most common strategy
employed for flood control. The failure of preventive measures has led to most authors
and researchers to advocate a shift in thinking from preventive measures to flood risk
and structural management measures. On the other hand, areas on the lee ward side of
the mountain like Karamoja experience water scarcity and basing on the flooding
conditions, this excess water causing flooding can be diverted. Recently, The
advancement in computer-aided technology has been extensively used in formulating
models used for flood calculation and hazard analysis. This study focuses on using a
hydraulic model HEC-HMS and HEC-RAS in a GIS environment for the affected areas
of Elgon zone i.e.Bulambuli and Kween, generates the inundation area and the return
period for the specified flood events. The research involved studying various literatures
and collecting data in form of journals and reports. This helped to formulate the
methodology for the whole project.
It was followed by the modelling stage. This started with data collection from various
Sources i.e .from offices. Data collected included:-DEM, discharge flow data, land
use/land cover data, rainfall data and soil data. These datasets were conditioned and
processed in the GIS environment using the ArcGIS software. Land use and soil data
was used to generate Curve number grid and later GeoHMS was used to set up a project
which involved basin characteristics and processing and exported into HMS to generate
hydrograph (peakdischarges) to be used in the HECRAS.The GeoRAS file was
exported to the HEC-RAS program to compute for a steady flow simulation. The RAS
mapper export from HEC-RAS program was then imported into ArcMap to delineate a
flood plain map which was overlaid to a Google image to determine flood prone areas.
The villages included among others like Chepsikunya,Ngenge,and along Mbale
Moroto road. This was followed by design of the system components like pipes,
reservoir tank, trapezoidal flood channel and sluice gates and there after simulating the
flow in Epanet.
