Institute of Technology

Permanent URI for this communityhttps://etd.hu.edu.et/handle/123456789/66

The Institute of Technology focuses on education, research, and innovation in engineering, technology, and applied sciences to support sustainable development.

Browse

Search Results

Now showing 1 - 10 of 13

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 ABEBE
The 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.
ASSESSMENT OF THE RUN OF THE RIVER HYDROPOWER POTENTIAL AT THE DOWN STREAM OF KOKA DAM AND FORECASTING THE LEVEL OF FLOODING AT SELECTED SITE (CASE STUDY OF AWASH RIVER BASIN, ETHIOPIA)
(Hawassa University, 2023-10-26) ASHENAFI AYZA ASELE
Energy demand is increasing exponentially. This is because of rapid population growth, urbanization, the higher standards of living, industrial and agricultural expansion. Nevertheless, the available energy supply is not reliable due to sedimentation problem. So, it is advisable to use the nearby available natural resources (i.e. river and suitable topography) for potential assessments without adverse effect to cope with increasing and diversified energy demands. This study aims to investigate the assessment of river run of hydropower potential at 50km downstream of Koka Dam. To achieve the goal, Stream flow data were collected from 1991-2016 and height information was quantified from contour map and 3D spatial analyst tool in ArcGIS. Initially, the study was identified three possible potential sites and from these sites; site one was selected as the most prioritized site using MCDA method. The study included the Flood level forecasting at mostly prioritized site for further precaution using HEC-GeoRAS for preprocessing of geometric data and HEC-RAS for post processing of hydraulic modeling. Following the aforementioned model, methods and data the study computed the theoretical power at site one was (8981kw and 4197kw), technical power was (6960kw and 3253kw) and the annual energy output was (60.9GWh/year and 28GWh/year) are the maximum and minimum power at Q30 and Q95 respectively. The most preferred site had dependable flow of 19.71m3/s and is occur 95% of the year and the design flow was 42.17m3/s and is occur 30% of the year. The flood inundation area and the maximum flood depth at mostly prioritized river station 1100 where the study starts head measurement (i.e. upstream full reservoir level) and around 1km upstream of R.S. 1100 (i.e. at R.S.2050) were (145.79m 2 , 4.96m) and (204.09m 2 , 5.62m) respectively for 100 year return period. The validation of spatial information for site one tested were 0.71 for RMSE and hydraulic model performance for R.S.1100 and R.S.2050 were (0.7, -8.29 and 0.97) and (0.83, 5.92 and 0.96) for ENS, PBIAS and R for return period of 100 year and show the applicability of the model was good. To encapsulate we can get the site at 50km downstream of Koka Dam that have the capacity to produce annual energy of 60.9GWh/year. Consequently, it is possible to minimize the problem of highly increased and diversified electric demands at the target area. Hence, it is recommended that the government at national as well as local level or any other agency should look over it in detail and finding to implement thorough investigation of the area
FLOOD MAPPING ON GREAT AKAKI RIVER IN ADDIS ABABA, AKAKI KALITY SUB-CITY
(Hawassa University, 2019-12-19) BERHANU BALTA HADARO
In 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.
PERFORMANCE ASSESSMENT OF STORM DRAINAGE SYSTEM, THE CASE OF WELKITE TOWN ,CENTRAL ETHIOPIA REGION,ETHIOPIA
(Hawassa University, 2023-10-16) TAMIRAT AMDE
Most storm water drainage problems investigated with respect to its hydraulic performance.In Wolikite town drainage structures are not well-designed to carryout the runoff due to blockage & capacity on size of the ditch.The objective of this study is ,to assess storm water drainage system performance of the town. The study employed both primary and secondary data collection. To achieve the specific objective HEC-RAS model analysiss has been used to calculate peak discharge and the averge rainfall using log pearson type III, in order to develop the Intensity Duration Frequency (IDF) curve for the rainfall intensities recorded in different duration and analyzed for a period of 1991-2021. Detail evaluation of drainage channels is required to control damages on high storm. For sizing of existing and proposed drainage channels manning formula is used and the hydrological peak flow was determined by using Rational Method. It was found the discharge using rational method is that 1.78mcu , and the result from the HEC RAS model 0.08mcu compared with existing hydraulic capacity of the channels . It shows that study area storm water was higher with respect to the drainage channels to carry the expected runoff during high rainfall events, make incapable to carry the runnoff for drainage ditches of the study area. To resolve these problems BMP’s have been recommended and finally, the analysis from this study permits future work on re design of the town storm drainage ditches and resettlement of flood affected areas and amend land use of the town for residential should be considerd in connection with town master plan development
DAM BREACH MODELING and INUDATION MAPPING A CASE STUDY OF JEMA DAM, ABAY BASIN, ETHIOPIA
(Hawassa University, 2018-08-13) AMDEMARIAM SHIFERIE MULU
Preparing 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 dam
DAM BREACH ANALYSIS AND FLOOD INUNDATION MAPPING FOR GIDABO DAM
(Hawassa University, 2019-03-15) FIRAOL BEFEKADU GELETA
This 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 dam
FLOOD RISK MAPPING USING HEC-RAS MODEL: CASE STUDY ON WAJA WATERSHED IN RIFT VALLEY BASIN CENTRAL ETHIOPIA REGION, ETHIOPIA
(Hawassa University, 2024-04-22) ATEREFE TAMIRAT DEBOCH
Flood is among the most devastating natural disasters worldwide, significantly affecting human lives and property. The current study conducted on the Waja River floodplain aimed to model and maps the flood inundation, flood hazard, flood vulnerability, and flood risk associated with flooding in the area. To achieve this objective, various data sources were utilized, including meteorological, hydrologic, and topographic data collected from different organizations. The study employed several tools and materials, including the HEC HMS and HEC-RAS models, GIS software, GPS devices, and metering tape. The HEC HMS model was used to analyze flood hazard and risk by developing inflow design floods for different return periods. The model was calibrated and validated using actual stream flow data. During model calibration the NSE value was 0.75, Percent Bias (PBIAS) was 2.02, coefficient of determination (R2 ) was 0.78, and Relative Mean Square Error (RMSE) was 2.03. During the validation period, the model achieved an R2 of 0.77, NSE of 0.76, PBIAS of 1.64, and RMSE of 1.3. After calibration and validation, the annual maximum precipitation from rainfall data was extracted to develop frequency storms for different return periods. These storms were then used as input for the HEC HMS model to generate flood hydrographs. The HEC-RAS model, combined with the flood hydrographs, was used to produce flood inundation maps, which were visualized in ARC-GIS software for detailed analysis. The results of the study indicated that for return periods of 10, 25, 50, and 100 years, the areas inundated by floods were 3030 ha, 3364 ha, 3520 ha, and 3683 ha, respectively. Additionally, the maximum flood depths were found to be 6.3m, 9.2m, 12.6m, and 14.45m for the respective return periods. The maximum flood velocities were 3.8 m/s, 4.7 m/s, 5.5 m/s, and 6.8 m/s for the same return periods. Flood hazard maps were derived from the depth, velocity, and duration of floodwaters, revealing that 35% of the flooded area was categorized as having very high and high hazard, while approximately 65% was classified as medium and low hazard. The flood vulnerability map classified approximately 17% of the flooded area as having high and very high vulnerability. About 18% of the flooded area fell into the moderate vulnerability class. The majority of the flooded area, approximately 65%, had low and very low vulnerability. By combining the flood hazard and vulnerability information, the study developed a flood risk map. The results showed that 24% of the area fell into the high and very high-risk categories
FLOOD INUNDATION MODELING AND RISK MAPPING OF BIG AKAKI RIVER, ADDIS ABABA, ETHIOPIA
(Hawassa University, 2023-03-06) GIZACHEW MUSIE ALENBO
The occurrence of floods as natural disasters has severe consequences worldwide, including loss of life, the spread of diseases, property damage, economic hardships, and social and psychological impacts on affected individuals. This study focused on modeling and analyzing the flood inundation and associated risks of the Akaki River, located in Addis Ababa, the capital city of Ethiopia. The primary objective of this study was to create models and maps that depict the extent of flood inundation and the risks associated with flooding events. To accomplish this, both primary field data and secondary data from various sources was collected. The materials utilized in this study included the HEC-RAS model, GIS software, GPS, and metering tape. The study involved conducting a hydrologic flood frequency analysis for different return periods, which served as input for flood inundation modeling and risk analysis. The HEC-RAS model was employed to develop flood inundation, flood hazard, flood vulnerability, and flood risk maps, which were subsequently mapped using ARC-GIS software. The results of the study revealed that the areas affected by floods varied depending on the return period. For return periods of 10, 25, 50, 100, and 200 years, the areas inundated by floods were measured to be 7.58 km², 9.79 km², 11.2 km², 12.45 km², and 13.83 km², respectively. The study also determined the maximum flood depths and velocities for each return period, with values ranging from 10.21 to 15.02 meters and 3.12 to 5.26 meters per second, respectively. Based on the flood hazard map for the 200-year return period, it was identified that approximately 13.7% of the total flooded area was categorized as an extreme hazard, rendering it unsafe for all individuals, vehicles, and structures vulnerable to flooding. Additionally, 17.6%, 16.7%, 18.9%, and 33.1% of the total area fell under the categories of very high, high, medium, and low hazards, respectively. The flood vulnerability map highlighted five levels of vulnerability, ranging from very low to very high. The very high and high vulnerability classes covered 9.59% (1.21 km²) and 15.54% (1.96 km²) of the flooded area, respectively. Furthermore, the flood risk was classified into five levels, revealing that 3.6%, 12.6%, 18.5%, 19.8%, and 45.5% of the flooded area were associated with very high, high, moderate, low, and very low risks, respectively. Considering the high risk and danger posed, particularly to residents residing in the flood buffer zone, a proposed solution to protect the area from flood hazards involved the construction of a 5.83 km levee embankment along the settlements on the left side of the river, specifically in areas with high population density. Finally, the performance of the HEC-RAS model was evaluated using model evaluation statistics, resulting in a coefficient of determination (R2) value of 0.94 for the water surface elevation, indicating a strong correlation between observed and simulated data. This study provides valuable insights into the flood dynamics, risks, and vulnerabilities associated with the Big Akaki River in Addis Ababa. The findings can inform decision-making processes aimed at mitigating the impacts of floods, protecting vulnerable populations, and enhancing overall flood management strategies in the area
FLOOD HAZARD MODELING AND RISK MAPPING: CASE STUDY ON LOWER WEITO RIVER RIFT VALLEY BASIN SNNPR, ETHIOPIA
(Hawassa University, 2025-08-12) GELMA BORU
This study focuses on the modeling and mapping of flood inundation and associated risks in the Lower Weito River, a tributary of Lake Abaya by means of coupled hydrological and hydraulic models with different return periods. Meteorological, hydrologic, and topographic data were collected from various sources. Rainfall data from 1990 to 2015 were collected from the National Meteorological Agency and the stream flow data from 1990 to 2007 were collected from the Ministry of Water and Energy. DEM 12 * 12m resolution was downloaded from Alaska satellite facility, soil data was taken from FAO and LULC data were collected from the Ministry of Water and Energy. These data were integrated using modeling tools such as HEC-HMS and HEC-RAS, along with GIS software. To examine the accuracy of the HEC-HMS model, calibration and validation is performed using observed stream flow data. The results showed a strong relationship between simulated and observed data, with R2 and NSE values of 0.82 and 0.77, for calibration periods and 0.78 and 0.75 for validation period respectively which indicating a very good agreement between observed and simulated flow . The calibrated and validated model was then used to develop flood hydrographs for different return periods based on frequency storm analysis. The result of flood frequency analysis showed minimum peak flow of 77.9m 3 /s for a 2-year return period with 24-hour storm duration and, the maximum peak flow 606.2 m3 /s occurs with a 100-year frequency storm for the same duration. The HEC-RAS model was used to generate flood inundation maps, which revealed the extent of flooded areas and the maximum flood depths and velocities for various return periods. The results indicated that the areas inundated by floods ranged from 1711.2 hectares for a 10-year return period to 2763.3 hectares for a 100-year return period. The maximum flood depths varied from 5.2 meters for a 10-year return period to 7.5 meters for a 100-year return period. The maximum flood velocities ranged from 3.15 meters per second for a 10-year return period to 7.01 meters per second for a 100-year return period. Flood hazard maps were derived by considering the depth, velocity, and duration of floodwaters. The results showed that about 0.01% of the total flooded area was under extreme hazard, 14% under very high hazard, 29% under high hazard, 35% under medium hazard, and 21% under low hazard. The flood vulnerability map classified the flooded areas into five vulnerability classes. Approximately 44% of the flooded area was classified as high and very high vulnerability, 19% as moderate vulnerability, and 37% as low or very low vulnerability. The flood risk map was developed by combining the flood hazard and vulnerability information. The results showed that 16% of the area was classified as very high to high risk, 46% as medium risk, and 38% from low to very low risk.
FLOOD MAPPING ON GREAT AKAKI RIVER IN ADDIS ABABA, AKAKI KALITY SUB-CITY
(Hawassa University, 2019-07-08) BERHANU BALTA HADARO
In 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

Institute of Technology

Browse

Filters

Settings

Sort By

Results per page

Search Results