One Dimensional Unsteady Flow Analysis Using HEC-RAS Modelling Approach for Flood in Navsari City

Abstract

Flood is a natural tragedy which occurs as a consequence of tremendous rainfall occurrence. Navsari city and part of villages nearby Navsari lie on the Purna river bank which is a flood affected region. The Purna River flood disturbs common people’s day to day life in the city as well as the surrounding villages nearby Navsari very frequently. The perception of the processes behind flood is required to provide a good and efficient way to protect areas at risk. The present study uses the Hydrologic Engineering Center’s River Analysis System (HEC-RAS 4.1.0) Model for the flood analysis. For the flood discharge of 2004 and 2013, water surface heights were calculated. The unsteady flow computations were carried out for the past flood events of the year 2004 and 2013 for High tide and low tide conditions separately for Purna Basin. A total of 128 cross sections along the main river close to the city were taken into consideration for unsteady flow simulations. The Purna river passes through the densely populated Navsari city which is more vulnerable to flood. In this study, cross-sections and past observed flood data have been used to develop a 1-D integrated hydraulic model of Purna River. The calibrated HFL value was also validated with the observed HFL value. The result shows that the selected study area was more affected by the flood. In order to avoid the losses due to floods in future, it is recommended to increase the height of embankment, to provide stone pitches and embankment along the study reaches to prevent flooding of the adjoining areas.

Keywords: Purna River, HEC-RAS, HFL, Navsari, Flood