Hydrological and Hydraulic Behavior Studies about Urban Flood through Part of the Sari City

Urban watershed shows quite different hydrological and hydraulic behavior from natural watershed. Cities, that located along the Caspian coastline, have been flooded annually several times by relatively extreme storms and it creates a negative outlook in the cities. Comprehensive planning, design and management of surface water drainage systems are essential for creating a safe environment for the citizens. Computer models control urban run-off. Studying area is 39.64 (ha) that it was divided into 51 sub-basins. The simulation of flooding in urban catchment basins for this study was required information such as climatic, topographic, hydrologic regime, current status of surface water collecting network and hydraulic properties. In this study, urban flooding is simulated by MIKE SWMM model. By applying this model, in term of hydrologic and hydraulic data of the drainage systems, capability of surface water collecting system were evaluated for safe passage wandering water with design storm for 2, 4 and 6 hours and return periods of 2, 5, 10 and 25. The critical nodes and channels were identified after simulation. In result, simulation also showed that some existing water channels in this region, have not capability of passing design floods and this inability causes extra load and creates flooding condition in ending nodes over critical routs. Thereby, this long-time condition creates serious difficulties in transportation system and make inundation in the roads.