1D Unsteady Hydraulic Modelling of Purna River Reach to access Urban flood using HEC- RAS

Flood is the most common and widespread disaster which cause damage to property, crops and other negative impacts on human society. The understanding of the processes behind floods is required to provide a good and efficient way to protect areas at risk. In this study, 1- D unsteady model of Purna River is performed using HEC-RAS. The Purna River passess through densely populated Navsari city which is more vulnerable to flood. In this study, cross-section and past observed flood data have been used to develop 1-D integrated unsteady hydraulic model of Purna River. The flow computations are carried out for Past flood event of 2004 for High tide and low tide condition separately for Purna Basin. To developed 1-D model, 453 cross-sections on main river and 135 cross-section on tributary were taken into consideration. From the analysis, the critical villages and near by areas of purna river which submerged was identified. The calibrated HFL value was also validated with observed HFL value also.The result shows that selected study area is more affected by flood. To avoid the lossess due flood it is recommended to increase height of embankment, to provide stone pitches and embankment along study reach to prevent flooding of adjoining areas.