The objective of the study is to assess adequacy of Drainage structures of Bila town. The studyrnemployed both primary and secondary data collection. The primary data collection were observationrn(field visit), and photographs that show the existing drainage structure conditions and information thatrnwere gathered from the residents about the drainage structures during the rainy season. The secondaryrndata sources were master plan of the town, rainfall data, and demography of the area, socio economyrnof the town, land use land cover information and climatic condition. rn Daily rainfall data is obtained from nearby Nedjo rain gage station. Consistency of the rainfall wasrnchecked With Double mass curve analysis using rain gage stations Gimbi, Dengero, Deddessa, Ayirarnand Dembidollo and fitting distribution frequency is checked using log Pearson type III method. rnThe catchment is divided in to 5 small sub catchments, 13 conduits, with 13 junction nodes and 5rnoutfall. Tape meter and GPS is used to obtain dimension width, depth and elevation of each drainagernstructures. Sub catchment Imperviousness is obtained using land use land cover data and percentagernof imperviousness for different land surface. rnHydrologic analysis and hydraulic analysis was carried out by EPA SWMM 5 in which used tornsimulate response of catchment to rainfall events in which runoff, water depth profile, node surcharge,rnoutfall loading, node flooding ,link flow and conduit surcharge are obtained. Runoff is also obtainedrnfrom rational formula for comparison purpose. Parameters needed for rational method are taken fromrnERA manual. And selected extreme daily event was disaggregated into hourly events using reductionrnformula. At point culvert found is where outfall loading obtained therefore maximum discharge andrnpeak discharge is used to analysis culverts using HY-8 culvert analysis tool. rnThe results from the model show that there are nodes flooded, storm water network system has beenrnnot well planned and has not sufficient carrying capacity to satisfy the simulated rainfall event. rnThen storage facilities Detention pond was proposed for reduction of flooding effect at downstreamrnwhere coffee plant is affected rnFinally appropriate recommendation is given in order to have a standardized and harmonized urbanrndrainage systems