Hydraulic Modeling and Flood Mapping Of Fogera Flood Plain: A Case Study of Gumera River

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Addis Ababa University


Nowadays, extraordinary floods are common many parts of Ethiopia causing a lot of losses to human lives as well as damage to property. Historically, Fogera/Dera flood plain has been vulnerable to flash flooding from rainfall, in particular of the Gumera catchment which passes in between the Fogera -Dera weredas. The tributary rivers are originating from the southern highlands of Debretabor with a steep slope. The Fogera –Dera flood plain is located east of Lake Tana in North West Ethiopia about 625 km from the capital city Addis Ababa and the terrain is fairly flat. The Gumara catchment drained by Gumara River is part of Nile basin The over flow of the river affects part of the Fogera /Dera flood plain but mainly the Fogera part at lower reach near to Lake Tana. Hence, this thesis is to identify peak flood and delineate and produce flood inundation mapping areas that can be affected by extraordinary floods and to recommend mitigation measures. This thesis tries to consider more options and fills the gaps not covered by others, adopting more than seven application soft wares like Arc GIS, Global Mapper, HEC-HMS, HEC-DSS, HEC-GeoHMS, HEC-RAS and HEC-GeoRAS. 30m*30m resolution DEM for the catchment and 2m contour interval for Fogera flood plain are used to analyze terrain information. For precipitation modeling, the daily rain fall basis is used for HEC_HMS calibration and ERA Intensity-frequency-duration curve is used for frequency storm analysis. The hydrologic frequency model is used for determining the peak flow discharge for return periods of 2, 5, 10, 50 and 100 years and the result is found to be 197.7m3/s, 246.8 m3/s, 265.4m3/s, and 306.0m3/s and 319.60m3/s respectively. For the 100 year flood frequency the maximum depth of flood is 7.94m and this depth of flood is extended to the flood plain up to 10km of the flood area which affects mainly the Wageta, Kidist Hana, Shina, Quhar Michael and Bebeks Tana mistily and Jigna Weredas .The total area affected by this flood is31.36 km2 and the area affected by the 2year flood inundation of 7.36m is 22.27 Km2.