Temporal changes in extent and duration of flooding in the Ganges-Brahmaputra Delta, Bangladesh

Abstract:

Bangladesh is a country that comprises much of the world’s largest delta containing the Ganges and Brahmaputra Rivers. Flooding is a fact of life in Bangladesh where up to two-thirds of the country is flooded annually from combined monsoonal rains and Himalayan snowmelt. For this reason, understanding flood dynamics on both local and regional scales is critical. However, flood hazard studies to date typically rely on single flooding events to create flood maps and to evaluate flood hazards using satellite imagery. We use geographic information systems (GIS) to analyze hydrological time series data from the Bangladesh Water Development Board. Weekly data from 304 river gauges and over 1,200 groundwater gauges were used to map and model annual flooding events from 2003-2012. These data are useful because of the large temporal detail they will provide, which some satellite imagery can not. Spatial and temporal analysis techniques give insight into flooding and precipitation trends at the country and administrative district level. While precipitation has remained relatively constant through the time series, the average country-wide inundation depth has been decreasing. This trend could possibly be associated with improved flood management strategies in not only Bangladesh, but surrounding countries that are within the Ganges-Brahmaputra watershed.