Assessing the Status and Effectiveness of dykes in Lower Karnali River Basin, Rajapur Municipality, Bardiya, Nepal

Different flood adaptation techniques have been employed in Rajapur to prevent and control flood, but flood is still a problem there. One of the adaptation measures is the construction of dykes along the Karnali River. This study examines the status as well as effectiveness of dykes in Lower Karnali River Basin, Rajapur. Firstly, the design of the dykes is compared with some guidelines and the coordinates of areas which are in need of maintenance are collected and mapped on QGIS. Similarly, the impacts before and after the construction of dykes are compared in this study. In less than a decade of construction of dykes, it has breached in multiple locations; flooding Rajapur on several occasions. In addition, the dykes is not continuous: resulting areas without dykes vulnerable to flooding. Moreover, the breakage of dykes as well as the run off coming from Geruwa Municipality might be responsible for flooding in Rajapur almost every year. The study also found that the poor drainage system for the accumulated water on the land ward side into the river causes water logging for a long time. Similarly, spurs were also deteriorating in multiple locations and sediment deposition was high between spurs. The erosion of agricultural land and complete destruction of houses was found to be significantly lower after the construction of dykes, although prevention of flooding has not been achieved. This study suggests for more research to identify and monitor weak points on the dykes using fluid dynamics principles and hydraulic engineering software.