Thesis Paper On Application of GIS in Cross Drainage Structure (Case study taken on major drainage structure on Goro-Akaki road)

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Addis Ababa University


Cost of most highway projects can be attributed to the design and construction of drainage facilities such as bridges, culverts, storm drains etc. The design of these structures involves hydrologic analyses to determine the design discharge and hydraulic analyses to determine the conveyance capacity. Although most hydrologic and hydraulic calculation procedures are now available as computer programs, which can significantly reduce the mathematical effort involved, substantial effort is still necessary to manipulate the data required for input into these programs. Traditionally the data generated to support these programs have been extracted manually from maps and cross-sections presented on paper drawings, however by building a digital spatial database of the hydrologic features, a GIS in conjunction with this database, the extraction of data and application of design procedures will become automated and more efficient. In this research study a GIS support system has been developed to assist in the design of highway drainage facilities. The selected case study is on tributary of the main Akaki River which is located in Addis Ababa. By utilizing hydrologic spatial data to calculate the input parameters such as catchment area and flow direction for standard hydrologic software packages. This GIS support system reduces the analysis time and improves the analysis accuracy by integrating digital spatial data that describe the watershed of interest with hydrologic theory. This helps in selecting methods of hydrological analysis based on the existing situations. Hydrology model is an essential tool for use in simulation, planning and management of rainfall and runoff processes. It is designed in a simplified way for quantitative and qualitative modelling at the hydrological processes. In this study, HEC-HMS version 3.2 is used to simulate stream flows for the tributary of Akaki river catchment which is located in Goro-Akaki road. Precipitation data used for calibration is collected from IDF curves of the region for 10, 25, 50 and 100 return periods the results obtained for return period of 100 is 504.3m3/sec and the high-water mark is 2164m which is lower than manually computed peak discharge and high water mark. The accuracy of simulation is highly dependable on the suitability of the parameters and accuracy of data used in the calibration and validation process. Results of simulation can be generated in hydrograph, summary table and time series table. The correlation of coefficient (R2) and root mean square (RMSE) are used to evaluate the prediction of HEC-HMS model. Key words: GIS, hydrological analysis



GIS, Hydrological analysis