Flood Hazard Zonation in Jiadhol River Basin of Assam

Jiadhol River is one of the most frequently flooded north bank tributaries of Brahmaputra. It has a basin area of 1094.93 sq kms, of which 38 % lies in Arunachal Pradesh and 62 % in Assam. There are many factors responsible for the intensification of floods in this basin. Flood management is very important in this river. Flood hazard zonation of the basin helps in proper management and adaptation of the floods in the basin. This paper aims to develop a simple method for flood hazard zonation of the basin by applying GIS. The method used here is multi-criteria weighed overlay analysis of GIS. This method includes many factors such as geomorphology, elevation, slope, drainage density, drainage network, flow accumulation, soil, groundwater table and land cover/land cover, lithology and also proximity to drainage, confluence, and embankment breaching point for flood hazard zonation. All factors are weighted according to their role in the occurrence of floods. Using the mentioned method, four hazard zones are derived, they are the severely flood-prone zone, moderately flood-prone zone, less flood-prone zone and flood free zones consisting 31 % 18 %, 15 % and 36 % of the basin respectively. Most of the upper basin comes under flood free zone except the river valleys. There are two distinct severely flood-prone zones in the lower part of the basin. The hazard zonation derived in the paper has been validated with the real-time flood data collected at the block level and is found relevant in identifying the severely flood-prone areas.