JBS Vol 20. Num 2. 2018 - Underlying Causes of Early Floods in the Haor Region

Md. Khalequzzaman

Four haor (vast wetlands) districts (Sunamganj, Sylhet, Netrokona, and Kishoreganj) in NE Bangladesh suffered an unprecedented flood in late March-early April of 2017. Though not as extensive, parts of the haor region was affected by hail storm and early flood in April of 2019. 

This study analyzed underlying causes of these untimely floods using the rainfall data available in public domain for Cherapunji, West Garo Hills, West and East Khasi Hills, and Jaintia Hills in Meghalaya State of India, and Sunamganj in Bangladesh for the period of 1901–1917. Geomorphic analyses of stream cross sections in the haor region indicate that water carrying capacity of these streams are critically insufficient to effectively discharge the generated surface water run-off that results from major rainfall without causing flooding.

The results of data analysis reveal that the rainfall patterns during the months of April and May have changed during 1959–2017 period when compared to the rainfall patterns during 1901–1958 period. Analysis of monthly rainfall data indicates that flooding in early April is likely to become more common in the future, which is compatible with the concerns expressed in the IPCC reports. The study also concludes that the carrying capacity of rivers in the haor region has substantially declined over the last few decades due to siltation in riverbeds and land-use changes in the watershed area, which is likely to be responsible for an increase in flood inundation and duration in recent years. This study recommends to increase water carrying capacity of haor rivers through widening and deepening of river channels, especially at Bhairab Bridge outlet point, to accommodate expected surface run-off. Adopting an integrated water-sediment-land-use management plan at watershed scale involving all stakeholders and co-riparian nations is essential for successful solution of flooding problems in the haor region.