Developing Maximum Intensity Duration Frequency (IDF)Curve to WolaitaSodo City, Ethiopia

Modern integrated urban planning and development practice often includes time of concentration and Rainfall- Intensity-Duration [IDF] to derive storm runoff which is important to design capacity of drainage system, culvert, bridge and related hydraulic structure. Intensity-Duration-Frequency (IDF) curves describe the relationship between rainfall intensity, duration and return period. In Ethiopia, it is not usual to use IDF as basic hydrologic tools, in the planning and hydraulic design especially urban hydraulic related structure and often implemented based on assumptions. The aim of this study was to develop IDF curve which can be used in planning, design of hydraulic structure, estimation of flash flood risks and decision of protection measures at down part of town and updating rainfall characteristics for climate change in WolaitaSodoCity. To develop IDF curve annual maximum observed precipitation of 32 years [1986-2017] from ground located gauge in the town used. The IDF curves were established for return period of 2,5,10,25,50,100 and 200 to rainfall duration in minutes from10- 240 minutes by disaggregating daily observed rainfall to short duration and predicting extremes .To develop empirical equation formulated by using regression analysis fitting power expression and area constants are C,m,e are 271.57,0.1305 and 0.717 respectively.The study result recommended engineers and decision makers to use the IDF curve as decision support in need of related projects.