Floodplain Zone Modeling by Using HEC-RAS Model in Rushikulya River Basin of Ganjam District, Odisha, India

Mapping sensitivity of flood prone zones is one of the foremost activities for managing them. Keeping this in view, the present study was conducted with the main objective is to map the flood prone zone of River Rushikulya basin of Ganjam district in Odisha. The floodplain zone was modeled by using HEC-RAS in order to identify the total flood prone area as well as agricultural area that will be affected by flood at various water levels. With an increase of water level by 4.5 metre (m) from the River Rushikulya banks, about 99, 051 ha. area can be flooded. Among this around 80% of this area is under agriculture. Flood prone area progressively increased from about29, 504 ha (3.5 per cent of district geographical area) at a water level of0.5 metre above river bank to about 99, 051 ha (11.9 per centof district geographical area) at4.5 metre. The analysis reveals that Aska block is the most sensitive area for increase in river water levels. Besides Aska, Purushottampur, Ganjam, Kabisuryanagar, Bellaguntha, Hinjiliand Jagannath prasad are identified as the most flood prone blocks with substantial area under agriculture. From this analysis, we conclude that the HEC-RAS model can be used for mapping floodplain zones of river systems in India even with limited input data sets. The first-flooded area is located in Kabisuryanagar block which may be taken as the warning point for flood risk. Using this approach, sensitive and first flood-prone regions can be identified for making flood management decisions and also to alert the subsequent flood sensitive regions.