ANNOUNCEMENTS
Basin of Mahanadi river experience very high frequency of flood and faces devastating impact of flood almost every year. This study is performed for a stretch of Tel river, a tributary of Mahanadi river which is a flood prone river. The study reach of river consists two gauging stations Kesinga (upstream) and Kanatamal (downstream). This study aims to show the important characteristics of Terrain based index over a physical model, and also how flood frequency analysis can be integrated into this. Flood plain mapping has been done in this study with use of both the above-mentioned models. ‘Height Above Nearest Drainage (HAND)’ is used as Terrain based index and HEC-RAS is physical model in which hydrodynamic modelling has been performed. ‘Flood Frequency Analysis’ has been performed using ‘Gumbel’, ‘Log Normal’ and ‘Log Pearson type 3’ distribution methods. To know the best suited distribution for the data, R2 and NSE values were considered between observed and expected data, on basis of it appropriate method was selected. Sensitivity analysis, Calibration and Validation has been done for the HD model. Flood hazard maps has been prepared for 2008 and 2010. The scenario generated by HD modelling for 100-year return period with the discharge value estimated by flood frequency analysis has been compared with the map developed with the help of HAND for same extreme event (100-year return period). At last Accuracy assessment was performed to check the similarity of flood plain developed from HAND with that of HEC-RAS. It was seen that HAND is giving good and reliable results, which means HAND was able to create almost similar flood extent with respect to HD modelling from the aspects of Meandering, Confluence, etc. But there are some limitations with threshold value determination for HAND. Overall HAND can be considered as an alternative for flood mapping for disaster management and near real time results.
Keywords: Hydrodynamic modelling, HEC-RAS, Terrain indices, HAND, Flood Frequency Analysis, Sensitivity Analysis, Calibration and Validation.
