Dam Breach Modeling and Flood Inundation Mapping For Middle Awash Dam
No Thumbnail Available
Date
2016-11
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
Addis Ababa University
Abstract
Analysis of dam breach events and the associated flooded area are helpful in the risk assessment
of dams. Because sudden failure of dam causes risk of flooding hazard to downstream area. The
objective of this study is to model the dam break and map flood inundation areas to be used for
estimating the potential consequence of dam breach and emergency planning purpose.
To meet these objectives materials used are HEC-RAS model in conjunction with
HECGEORAS an extension of ARCGIS for the case of Middle Awash Multipurpose Dam
which is located in Middle Awash sub-basin and DEM 30m of the area was used because of its
availability for the extraction of river geometries in HECGEORAS then exported to HECRAS.
In HEC RAS dam feature is entered as inline structure, and breach parameters were estimated
using the built-in parameter calculator in HEC-RAS and the PMF flow data is entered and
unsteady flow simulation is run. The flood map is done with RASMAPPER in HECRAS and
Exported to ARCGIS for further work.
Accordingly the Middle Awash dam has been checked for both overtopping and piping mode of
failure in HECRAS. The out flow hydrograph result was different for each breach method and
breach parameters which in turn affects the inundation area and hazard. It is also different for
both mode of failure in HECRAS.
The Middle Awash Dam was checked for overtopping failure with the PMF inflow and for
piping starting elevation at the center of dam which occur due to internal erosion of dam
material. The peak outflow hydrograph was routed down stream and flood inundation mapping
was produced. Failure with overtopping inundate 31000ha area and the failure of the dam with
piping inundate 30840 ha. The inundation extent, depth and hazard map of dam breach flood
shows that the towns at downstream Melkasedi, MelkaWerer and the cultivated area,
infrastructures, the animal and human life in the downstream can be affected with inundation
caused due to flood from dam failure.
The flood inundation map helps in estimation of the severity and extent of dam break flood,
warning time, consequence classification for emergency action planning and to alert the
government body. Therefore, damages that could occur in the surrounding settlements,
agricultural areas, on both lives and infrastructure can be minimized and even controlled
Description
Keywords
Accordingly the Middle Awash dam