Sand Dredging in Anyang River and its Implication on Morphological Structure in Edebom II, Nsit Ibom, Akwa Ibom State, Nigeria

Abstract

This study focused on sand dredging in Anyang Nsit River and its implication on morphological structure in Edebom II, Nsit Ibom, Akwa Ibom State, Nigeria, a third order tributary of Kwa Iboe river basin, which entails the morphometric parameters, dredging induced hazards, measurement and calculation of hydraulic parameters at two high dredging sites, are related to the dynamic nature of the river channel. Digital Elevation Model (DEM) of the study area with resolution 30x30m was obtained from United States Geological Survey (USGS) and the river channel was delineated. With the aid of Arc GIS 10.3 software package and Erdas Imagine 9.2 software reprojection and the map was produced in the layout view on a scale of 1:187500. The linear, areal and relief aspects of the sub-catchment were derived using strings and constructed grid lines placed on the map, while morphometric parameters of the river channel were calculated using relevant statistical package. The hydraulic parameters (bank full width, mean depth, velocity) of the two dredging sites were measured in a period of four months (MarchJune). The results showed that hydraulic parameters of these dredging points have changed significantly within this period. The calculated channel discharge had increased by 10m3/s and 7.42m3/s respectively at the two dredging sites. A total of 26,804 tonnes of dry weight sand is dredged both manually and mechanically (hydraulically) between March-June, 2021 which is consistent with the assertion that sand dredging is responsible for the change in the channel morphology especially in depth and deformation of channel configuration parameters. It was recommended that sand dredging in Akwa Ibom should be monitored by the Ministry of Environment as a statutory responsibility to maintain morphometric parameters in Akwa Ibom State, Nigeria.