Assessment of shafique haor and sonamoral haor schemes against flash flood in greater Sylhet area

Abstract

Flash flooding is one of the most recurring natural disaster over the northeastern region of Bangladesh. Haors are important areas for Boro cultivation as almost 80% of haor areas are covered by Boro rice. The farmers usually plant Boro crops in the floodplain in December and harvest from April to the first week of May. The Boro crop largely damage when flash flood occurs early May. For better water management and to facilitate crop production, Bangladesh Water Development Board (BWDB) has implemented about 118 schemes in the haor area to mainly protect Boro crop with some other functions like, drainage, irrigation, full flood protection. So, it is of utmost importance to understand and evaluate the performance of pre and post scenario of the implemented schemes against the flash flood frequency and Boro crop production. Therefore, a study has conducted to assessment the impact after implementation of the Flood Control, Drainage and Irrigation (FCDI) schemes against flash flood frequency and Boro crop production in greater Sylhet area. In this study, Shafique Haor scheme in Sylhet District and Sonamoral Haor scheme in Sunamganj District have been selected. To carry out the study, data of rainfall, discharge, water level, agricultural and Landsat satellite images have been collected from Bangladesh Meteorological Department (BMD), Bangladesh Water Development Board (BWDB), Center for Environmental and Geographic Information Services (CEGIS), Department of Extension (DAE) and United States Geological Survey (USGS) accordingly. In this study, hydrological and agricultural analyses have been carried out to assess the performance of Shafique Haor scheme and Sonamoral Haor scheme. Trend analysis, frequency analysis and Landsat satellite images analysis have been carried out under hydrological analysis. Under frequency analysis, Normal Distribution, Log-normal Distribution, Log-pearson type III and Gumbel’s Distribution have been considered. Normalized Difference Water Index (NDWI) has been calculated from the Landsat satellite images. In case of agricultural analysis, cropping pattern, cropping intensity, crop damage and crop production has been calculated. Impact has been assessed andsummarizedon changes in flash flood frequency and Boro crop production of Shafique Haor scheme and Sonamoral Haor scheme. In this regard, baseline has been created for pre-scheme scenario and post-scheme scenario for the identified indicators. Later, impact has been assessed by subtracting or comparing pre-scheme scenario status from post-scheme scenario status. It has been found that after implementation of the scheme interventions, risk of entrance of early flash floods reduced significantly. From the study, it has been also revealed that additional 5,466 ton and 1,327 ton crops have been produced in Shafique Haor scheme and Sonamoral Haor scheme accordingly during the post-scheme period. Therefore, Shafique Haor scheme and Sonamoral Haor scheme can be considered as complying with the objective to protect Boro crop from early flash floods and to facilitate crop producti