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Please use this identifier to cite or link to this item: http://hdl.handle.net/123456789/2832

Title: Flood Mapping and Modeling on Fogera Flood Plain: A Case Study of Ribb River
Authors: Zelalem, Abera
Advisors: Dr. Ing. Dereje Hailu
Keywords: HEC-HMS
Copyright: Jun-2011
Date Added: 9-May-2012
Publisher: AAU
Abstract: Flood occurs repeatedly in Ethiopia and cause tremendous losses in terms of property and life, particularly in the lowland areas. The majority of flood disasters’ victims are poor people living in nearby stretch of floodplain. Therefore, the study was carried out to perform floodplain analysis and risk assessment of Fogera and nearby areas. This research involves the integration of HEC-Hydrologic Modeling System (HECHMS) and HEC-River Analysis System (HEC-RAS) with Geographic Information Systems (GIS) to develop a regional model for floodplain determination and representation. The study describes the flood extent and depth in the area for different flow conditions derived from the historical flow data of the Ribb River. The hydrologic model is calibrated using HEC-HMS for hourly time series data for return periods of 2, 10, 50 and 100 years. The value derived by the hourly data of the HEC-HMS is compared with different frequency analysis methods. One dimensional hydraulic model HEC-RAS with HEC-GeoRAS interface in co-ordination with ArcGIS was applied for the analysis. Triangulated Irregular Network (TIN) was prepared from shape file generated from spot elevations of the floodplain through field survey data and the DEM of the study area in ArcGIS. Required data sets as stream centerline, banks, flow paths and cross sections were prepared in HEC-GeoRAS thus, creating import file and imported in HEC-RAS. In HEC-RAS, boundary condition for downstream were defined. Similarly, flood discharges for different return periods were also inputted and steady flow analysis was done for the results. The result of hydrologic model by HEC-HMS shows a flow value of 91.8m3/s, 202.4 m3/s, 273.1m3/s, and 308.4m3/s for return periods of 2, 10, 50 and 100 respectively. The result was compared with the frequency analysis using event flow values of the Ribb River. According to the food map, the flooded area for the return periods 2, 10, 50 and 100 years are 12.63km2, 18.63km2, 21.31km2 and 22.5km2 respectively. The classification of flood depth area showed most of the flooding area had water depth less than 1.5m. On the other hand 88% of agricultural land, 11.6% of agro-pastoral land and 1.36% River is inundated by the flood.
URI: http://hdl.handle.net/123456789/2832
Appears in:Thesis - Civil Engineering

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