Application of BRAHMA hydrodynamic model for flood forecasting

Abstract

Flood forecasting models are of paramount importance to predict the flood and thereby warning the community living near the floodplains or the vulnerable areas. In the quest for understanding the complex processes of a river, scientist and researchers have given importance to river modeling both analytically and physically by conducting experiments in the laboratory. The numerical model which is basically a mathematical model has gained popularity in the last few decades. BRAHMA (Braided River Aid: Hydro-Morphological Analyzer) is a hydrodynamic model for simulating the spatial variation in water depth, flows, and velocities in the unsteady free surface flow. It is developed by IIT Guwahati in collaboration with Brahmaputra Board, Govt. of India. The BRAHMA 1-D model is capable of simulating both prismatic as well as non-prismatic channel reach. It is also capable of simulating channels with varying width and varying slope. In this paper, an attempt has been made to use the BRAHMA 1-D model for determining the water surface elevation at certain flood-prone areas of Ranganadi River which covers Assam and parts of Arunachal Pradesh, North-East India. The Ranganadi hydroelectric dam is situated in Arunachal Pradesh, India. In this study, the length of the river reach considered is 77.09 km from the Ranganadi Hydroelectric power project. The cross-sectional width of the river in different sections is extracted from Google Earth and depth was obtained by approximate field measurement. The peak release from the dam, the downstream water level and initial water levels are given as input to the model. The water levels at the particular sections of interest are computed as output from the model. From the generated output data set, it is possible to assess the vulnerable areas by the water levels which will be generated from the model.