IMPACTS OF SAND MINING ON RIVER MORPHOLOGY

Current global rate of sand mining in river channels is unsustainable, and in Malawi the activity going on unregulated. This study established the morphological effects of sand mining in Luchenza by addressing the following objectives: To determine the: extent of sand mining; morphological factors influencing abundance of sand; effects of sand mining on the morphology of Luchenza River. Systematic sampling was used on this section to select the areas to collect data. Data on channel depth, width, vegetation cover, erosion status, sand volume status, channel slope angles, and bank position were obtained through physical measurements in the field. ArcMap GIS was used to map the spatial extent of sand mining along Luchenza river. The binary logistic regression analysis was employed to show factors influencing abundance of sand in Luchenza river channel. The study established that river channel width (P=6.47e-05), depth (P=7.00e-07), slope angles (P=3.36e-06) and bank position (P=2.2e-16) were significant in influencing sand abundance in the river channel as indicated by the respective marginal effects and pvalues. Additionally, sand mining had modified the river channel morphology through causing increase in depth (P=7.19e-02), width (P=9.95e-03) and slope angles (P=9.37e03) at the active mining sites, compared with the control sites as shown by the respective p-values. Field data analysis was combined with google earth imagery data for 2013, 2016 and 2024 using ArcGIS 10.8 software to see changes in river morphology, formation and extent of point bar and channel bar, as well as changes in the area of river water bodies and non-water river bodies. The results showed that the changes in morphology and physical dynamics conditions of the Luchenza River showed their own pattern. If sediment deposits forming point bars or channel bars were reduced, the area of river water bodies tended to increase. Or in other words, the width of the river is inversely proportional to the increase in the area of the river water body if the area of sediment deposits that form the point bar and channel bar tends to decrease

This study established the morphological effects of sand mining in Luchenza by addressing the following objectives: To determine the: extent of sand mining; morphological factors influencing abundance of sand; effects of sand mining on the morphology of Luchenza River. Additionally, sand mining had modified the river channel morphology through causing increase in depth (P=7.19e-02), width (P=9.95e-03) and slope angles (P=9.37e03) at the active mining sites, compared with the control sites as shown by the respective p-values. Field data analysis was combined with google earth imagery data for 2013, 2016 and 2024 using ArcGIS 10.8 software to see changes in river morphology, formation and extent of point bar and channel bar, as well as changes in the area of river water bodies and non-water river bodies. Or in other words, the width of the river is inversely proportional to the increase in the area of the river water body if the area of sediment deposits that form the point bar and channel bar tends to decrease

This research was conducted in Luchenza River which forms a boundary between Thyolo district and Chiradzulu district. Luchenza river section on which this study focused lies between longitude 8241373 and 8242425, and latitude 740155 and 736036 (Figure 1). Luchenza river is located in a mountainous area (refer to figure 3 below) which cause a lot of water to be directed to it during rainy season. This indicates that all eroded sediments are deposited in this river. Luchenza river was selected because sand mining is taking place unregulated thus causing negative environmental effects on the river

District: Chiradzulu

Coordinates: -15.76315, 35.21105