Diagnostic of the massive flood event and flood hazard mapping in Tons River basin

This study diagnoses the Satna flood event in the Tons River basin. The occurrence of this intense flood is attributed to the rainfall associated with the movement of the monsoon depression during the peak monsoon season. The study uses Weather Research Forecast (WRF) model to examine the origin, movement, and dissipation of the monsoon depression over India. The study also incorporates remote sensing techniques and field campaigns to better understand the impact on the areas. The model captures the origin of the monsoon depression and the highest precipitating days fairly well. However, it underestimates the rainfall magnitude with respect to different observations due to the limited ability of the model to capture the rainfall maxima spatially. Moreover, the conditional instability of the second kind (CISK) mechanism seems to drive the monsoon depression. A positive feedback mechanism is observed along the track of the depression between rainfall and convective activity leading to excess rainfall over the Tons basin. The remote-sensing-based analysis using Landsat 8 products shows that around 1309 km2 area of the Tons basin was inundated during the event. Based on the computed Flood Hazard Index values, the entire basin has been divided into the low, medium, high, and very high flood hazard zones with several affected hamlets 19, 178, 155, and 91, respectively. The flood hazard values are important for the planners to adopt appropriate adaptation and mitigation to minimize the impact of future flooding in the basin.