Alluvial Deposits and Their Effects On the Physical L Environment and Socio-Economic Activities On the Lower Course of River Kuja, Nyatike Division- Nyatike District, Kenya

Abstract

Alluvial deposits are features resulting from river deposition. They consist of gravel, sand and silt particles, formed on the lower course of a river. Deposition of sediments at the lower course of a river increases because of a decrease in the river flow and hence a reduction in the competence of the flow. This study focused on the lower course of River Kuja, approximately 5 km from the river mouth and 4 km away from the river channel on both sides of the floodplains. Continuous accumulation of sediments on the river channel makes the channel to become shallow in depth, thereby forcing water in the channel to go over the river bank, into the floodplains, carrying the river load into the farmlands and hence, an increase in soil fertility. Floods emerging from over bank flow can cause erosion of fertile soil along steep river banks, destroying crops, livestock and drowning homesteads of the inhabitants. The objectives of the study were to: identify types of alluvial deposits on lower course of River Kuja; determine the effects of alluvial deposits on the physical environment; find out the effects of alluvial deposits on socio-economic activities on lower course of River Kuja. A sample size of 384 households was obtained from a total of 20,000 households from the study area by the use of simple random sampling technique. Primary data was collected through Household Survey, Focused Group Discussions, Key Informant Interviews, Observation and Photography. Secondary data was collected by reviewing documented literature including reference books and from the internet. Quantitative data were analyzed by using descriptive statistics such as percentages. The study identified river channel deposits, the river bank and the floodplains deposits. Alluvial deposits can cause deep river channels to become shallow, cause over bank river flow into the floodplains, pools of stagnant water, soil erosion on steep river valley, drowning of homesteads and displacement of inhabitants from the floodplains. On socio-economicactivities alluvial deposits affects crop farming, livestock keeping, fishing and trading activities. The results indicated that alluvial deposits are found on the channel, on the river bank and on the floodplains, where they affect the physical environment and socio-economic activities. Research study recommends that the roads leading to the river bank be improved, to enable trucks to reach the river bank and collect coarse sand from the river channel; deepen the channel and hence reduce over bank river flow that causes floods on the floodplains, encourage cultivation of farms along the contours, give early warning to the inhabitants to vacate areas prone to floods. This will reduce losses incurred when their properties are destroyed by the floods and finally encouraging the farmers, fishermen and traders to join co-operative societies to help them in identifying appropriate market for their produce even during flooding events. This will discourage the farmers from selling their produce to the middlemen who exploits them during flooding events when they are faced with limited market. Consequently, this will help in improving the livelihood of the inhabitants and hence, economic growth of Nyatike Division.