Flood characterisation of the Haor region of Bangladesh using flood index

Abstract

The paper presents the flood characterisation of the Haor region in the north-east of Bangladesh. The region consists of a system of Haors, each of which is a saucer-shaped depression and interconnected by a river system. A portion of the Haor area, known as the deeply flooded area, consisting of about 15 Haors, was chosen as the study area. A 1D2D model, with one-dimensional model for the rivers and a two-dimensional model for the Haors, was developed. Flood hydrograph characteristics such as the rising curve gradient, flood magnitude ratio (with respect to the average discharge) and time to peak were assessed for different river floods. Using these characteristics an integrated flood index (FI) was developed. The FI is an aggregated indicator based on the flood hydrograph characteristics and indicates the relative overall severity of a flood. The spatial and temporal variations of the index were investigated as well. The computed FI at different locations of the region and for different flood hazard frequencies provide a broad understanding of the flooding characteristics of the region. The developed methodology can also be applied to other river basins to analyse flooding risk provided some historical flood data are available.