Institute of Technology
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The Institute of Technology focuses on education, research, and innovation
in engineering, technology, and applied sciences to support sustainable development.
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Item HYDRAULIC MODELING AND FLOOD MAPPING OF HAROSHA RIVER WITH HEC-RAS AND HEC-GeoRAS MODELS IN TIGRAY, ETHIOPIA(Hawassa University, 2017-10-27) MULUGETA TAREKE ABEBEThe Harosha river catchment is found in Tigray region in Raya Valley. This study area is surrounded by Waja and Tumuga catchment in the south and Harosha, Limeat and Harle catchment in the North and also it is the upper south part of the Raya valley catchment. The area is also dominated by undulating terrain with relatively steep to moderately steep and flatter slopes in the downstream of the catchment. Harosha flood plain has been vulnerable to high flooding from rainfall during rainy season. Also the main causes of these damages are land use changes from years to years and the main objective of this study is to estimate peak flood for various return period and prepare flood inundation mapping that can be used as decision support system for future intervention. The data used for this study was annual daily maximum rainfall, DEM, land use land cover map, and soil map and the flood frequency analysis of annual maximum daily rainfall was analyzed. The SCS rain fall-runoff method, HEC-RAS, HEC-GeoRAS and ArcGIS environment are used to determine the peak flood for different return periods. The simulation result for return period of 5, 10, 25, 50 and 100 year floods magnitude are 347.4, 383.7, 420.8, 443.6 and 463.1m 3 /s respectively. The maximum flood hazard and flow depth maps for a return periods of 5, 10, 25, 50 and 100 year are 84.6 and 3.36; 86.1 and 3.84; 86.9 and 4.35; 87.1 and 4.91; and 87.7 hectare and 5.89 m respectively with a maximum velocity of 4.6 m/s.Item FLOOD MAPPING ON GREAT AKAKI RIVER IN ADDIS ABABA, AKAKI KALITY SUB-CITY(Hawassa University, 2019-12-19) BERHANU BALTA HADAROIn recent years, the patterns of flood across all continents have been changing and becoming more frequent, intense and leading the people to face risks. Therefore, the risk should be investigated and quantified properly. The objective of this thesis was to develop flood inundation maps of Great Akaki river in Addis Ababa, Akaki Kality sub-city. Streamflow, digital Elevation model (12.5*12.5 m) resolution and land use data were used as an input for the RAS mapper in HECRAS model. The 2D-HECRAS and ArcGIS models were used for mapping the flood extent, depth and velocity for various return periods. The Mann-Whitney and Wald-Wolfowitz statistical tests were used to hydrological data test. The basic assumption in statistical flood frequency analysis for its homogeneity, independency and stationarity of the time series at 5% significance level. The Easy fit 5.0 software was used to fit and identify the parent probability distribution for the streamflow data. The frequency analysis result depicts that Log-Normal probability distribution with 3 parameters best fitted the flood time series. The estimated quintiles for 2, 5, 10, 25, 50 and 100 years return periods were found to be 210.29, 333.04, 453.16, 626.19, 769.75, and 925.41 m3 /s respectively. The 2D-HECRAS model output indicated that about 86,123,156,228,285, and 350 ha land has been inundated for an event of 2, 5, 10, 25, 50 and 100 years of return period respectively. The 100 years flood magnitude inundated about 78, 272 and 34 ha of irrigated command area, swamp area and population settlement respectively. Flood risk map was developed based on hazard and vulnerability indicators. A preliminary alignment of structural flood protection dike was identified with length of 1.5km at downstream and 0.5 km at upstream of bridge which would make 95% of the settlement area on the left bank safe. The study has shown that the middle and lower part the study area is more inundated than upper parts. Therefore, the affected areas were whether to be free of infrastructure development, investment and residence of people or construct flood protection structure in order to avoid the risk of flooding in the area especially closer to the Great Akaki River.Item DAM BREACH MODELING and INUDATION MAPPING A CASE STUDY OF JEMA DAM, ABAY BASIN, ETHIOPIA(Hawassa University, 2018-08-13) AMDEMARIAM SHIFERIE MULUPreparing dam safety plans and hazard management strategies are unquestionably vital, since lots of human lives have been lost and tremendous amount of economic crisis have been recorded from dam failure events throughout the world in history. Setting out risk management, emergency action plans or evacuation planning system to protect both lives and materials during sudden dam failure phenomena and resulting flood waves is highly essential. This thesis analyzed the probable failure of a dam under a set of pre defined scenarios, within the framework of a case study, the case subject being the Jema dam located at Amhara Region of Ethiopia. A probable maximum flood of Gilgel Abay river (tributary of Jema River) has been computed using Hershfield’s technique .Breach parameters prediction, peak outflow hydrograph were determined by HEC-RAS model based on available technical and geometric data. Different maps such as flood areal extent map, flood depth map and velocity map have been produced by HEC-GeoRAS. The worst scenario was found to be scenario three (when Jema dam failed by overtopping with PMF of Gilgel Abay River). Probable maximum flood of Gilgel Abay river by Hershfield’s technique was found to be 1726.28 m3 /s. The maximum breach discharge resulted from HEC-RAS model was 79,886.37m3/sec and the maximum area inundated by this flood in downstream was found to be 41.6km2 . The areal maps show that the part of command area at right side and farm in left side, Bikolo Abay Town and settlement villages to be prone to flooding. The depth and velocity of flood also depict that the downstream rural village near the river bank are under extreme hazard category and the maps reveals that Jema dam is categorized under high hazed damItem DAM BREACH ANALYSIS AND FLOOD INUNDATION MAPPING FOR GIDABO DAM(Hawassa University, 2019-03-15) FIRAOL BEFEKADU GELETAThis study presented the dam breach analysis and flood inundation mapping for Gidabo rock-fill embankment dam found in Southern part of Ethiopia. The geometrical data used for this study was extracted from the recently released ALOS PLASAR digital elevation model by Alaska Satellite Facility, which is having the spatial resolution of 12.5 by 12.5 meters. One dimensional unsteady flow simulation within HEC-RAS model was used to simulate dam breaching for both overtopping and piping failure scenarios. Dam breach parameters estimation was done for different empirical equations. Froehlich (2008) and Von Thun & Gillete methods was preferred since the results obtained for these methods are more approaches to the envelope curve developed for the historical dam failures for overtopping and piping failures, respectively. RAS mapper and ArcGIS tools was used to present the maps of spatial distribution of flood extent, flood depth and flood velocity, flood inundation, flood hazard maps of the study area. The breach parameters estimated for both overtopping and piping failure scenarios was provided the reasonable values. The maximum breach discharge simulated for overtopping and piping failure was obtained as 15,945.18 m3 /s and 14,904.18 m3 /s, respectively. Since the failure were tested for hydrologic failure and for normal water level condition, the magnitude of flood and the spatial distributions are obviously different. Developed inundation maps from this study could be possibly help as guidance for dam owners to develop the emergency action plan and for future expansion of irrigation project infrastructures, and other developmental activities around the downstream of the damItem FLOOD MAPPING ON GREAT AKAKI RIVER IN ADDIS ABABA, AKAKI KALITY SUB-CITY(Hawassa University, 2019-07-08) BERHANU BALTA HADAROIn recent years, the patterns of flood across all continents have been changing and becoming more frequent, intense and leading the people to face risks. Therefore, the risk should be investigated and quantified properly. The objective of this thesis was to develop flood inundation maps of Great Akaki river in Addis Ababa, Akaki Kality sub-city. Streamflow, digital Elevation model (12.5*12.5 m) resolution and land use data were used as an input for the RAS mapper in HECRAS model. The 2D-HECRAS and ArcGIS models were used for mapping the flood extent, depth and velocity for various return periods. The Mann-Whitney and Wald-Wolfowitz statistical tests were used to hydrological data test. The basic assumption in statistical flood frequency analysis for its homogeneity, independency and stationarity of the time series at 5% significance level. The Easy fit 5.0 software was used to fit and identify the parent probability distribution for the streamflow data. The frequency analysis result depicts that Log-Normal probability distribution with 3 parameters best fitted the flood time series. The estimated quintiles for 2, 5, 10, 25, 50 and 100 years return periods were found to be 210.29, 333.04, 453.16, 626.19, 769.75, and 925.41 m3 /s respectively. The 2D-HECRAS model output indicated that about 86,123,156,228,285, and 350 ha land has been inundated for an event of 2, 5, 10, 25, 50 and 100 years of return period respectively. The 100 years flood magnitude inundated about 78, 272 and 34 ha of irrigated command area, swamp area and population settlement respectively. Flood risk map was developed based on hazard and vulnerability indicators. A preliminary alignment of structural flood protection dike was identified with length of 1.5km at downstream and 0.5 km at upstream of bridge which would make 95% of the settlement area on the left bank safe. The study has shown that the middle and lower part the study area is more inundated than upper parts. Therefore, the affected areas were whether to be free of infrastructure development, investment and residence of people or construct flood protection structure in order to avoid the risk of flooding in the area especially closer to the Great Akaki RiverItem HYDRAULIC MODELING AND FLOOD MAPPING OF HAROSHA RIVER WITH HEC-RAS AND HEC-GeoRAS MODELS IN TIGRAY, ETHIOPIA(Hawassa University, 2017-03-10) MULUGETA TAREKE ABEBEThe Harosha river catchment is found in Tigray region in Raya Valley. This study area is surrounded by Waja and Tumuga catchment in the south and Harosha, Limeat and Harle catchment in the North and also it is the upper south part of the Raya valley catchment. The area is also dominated by undulating terrain with relatively steep to moderately steep and flatter slopes in the downstream of the catchment. Harosha flood plain has been vulnerable to high flooding from rainfall during rainy season. Also the main causes of these damages are land use changes from years to years and the main objective of this study is to estimate peak flood for various return period and prepare flood inundation mapping that can be used as decision support system for future intervention. The data used for this study was annual daily maximum rainfall, DEM, land use land cover map, and soil map and the flood frequency analysis of annual maximum daily rainfall was analyzed. The SCS rain fall-runoff method, HEC-RAS, HEC-GeoRAS and ArcGIS environment are used to determine the peak flood for different return periods. The simulation result for return period of 5, 10, 25, 50 and 100 year floods magnitude are 347.4, 383.7, 420.8, 443.6 and 463.1m 3 /s respectively. The maximum flood hazard and flow depth maps for a return periods of 5, 10, 25, 50 and 100 year are 84.6 and 3.36; 86.1 and 3.84; 86.9 and 4.35; 87.1 and 4.91; and 87.7 hectare and 5.89 m respectively with a maximum velocity of 4.6 m/s.