Morphological and Socio-Economic Effects of Sand Mining on River Tyaa in Kitui County, Kenya
Muiruri, Philip Gathogo
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Current global rate of sand mining in river channels is unsustainable, and in Kenya the activity going on unregulated. This study established the morphological and socio-economic effects of sand mining in river Tyaa 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 River Tyaa and Socio-Economic effects of sand mining in river Tyaa. Random sampling technique came up with an active sand mining site. Systematic sampling was used on this section to select the areas to collect data. Stratified sampling was used to select respondents using the records from M.S.M.C.S. This sample size comprised of 100 households, 50 sand miners and 5 land owners. 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 while data on sand quantity mined per year for a decade was obtained from secondary sources. Structured questionnaires were used to obtain socio-economic data. ArcMap GIS was used to map the spatial extent of sand mining along river Tyaa. Descriptive statistics was used to analyse the quantitative data and the results presented in graphs and percentages. The binary logistic regression analysis was employed to show factors influencing abundance of sand in river Tyaa’s channel. The multiple logistic regression analysis was used to examine the effect of sand mining to the river Tyaa channel morphology. Finally, chi-square test was used to test the hypotheses. Chi-Square test indicated that there were significant sand mining activities in river Tyaa (Df = 1, χ2= 9, P=0.003). 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 p-values. 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=9.37e-03) at the active mining sites, compared with the control sites as shown by the respective p-values. Finally, sand mining had caused positive economic effects (Df = 3, χ2= 201.65, P=0.000) such as reduced school dropout rates, infrastructural developments, enhanced livelihoods as well as affordability of medication. On the other hand, sand mining got associated with destruction of the riparian vegetation, lowering of water table in the sand reserves, prostitution, community conflicts and drug and substance abuse (Df = 3, χ2= 42.33, P =0.000). The study concluded that sand mining had over stretched on temporal, spatial and quantity basis; that sand abundance in a river channel is a factor of channel width, depth slope angles and the type of the bank. Further, the study concluded that sand mining had caused increased river channel depth, width and slope angle and that sand mining had caused significant Socio-Economic effects. The study recommended reduction in quantities of sand mined from river Tyaa through curbing illegal mining and closure of some mines; siting of mines on convex banks by regulatory authorities such as NEMA; Regular EIA as well as EA was recommended as a way of monitoring the activity. Lastly, the study recommended placement of an elaborate revenue collection system from sand mining industry by the county government to help give back to the community, and increasing involvement of the local area members in the sand mining industry to help resolve resultant conflicts.