Drivers and Effects of Gully Erosion on Communities in Suswa Catchment, Narok County, Kenya: a Geospatial Approach

Abstract

Soil erosion is a serious issue in Arid and Semi-Arid lands and affects community livelihoods and soil conservation efforts. This study was undertaken in Suswa Catchment, Narok County. The objective of the study was to assess land use and land cover changes(1985-2011) using satellite images, to establish the drivers of gully formation and development using participatory geographic information systems (PGIS) and also to determine the effect of gully erosion on the livelihoods of the local community. Land use and land cover change detection was established using ENVI Ex software. Changes in land use and land cover changes were determined using remote sensing and participatory geographic information systems (PGIS). Chi-square was used to determine if there were significant changes in land use and land cover changes. A questionnaire was used to investigate the effect of gully erosion on livelihoods (movement, infrastructure, livestock and farming practices). Chi-square goodness of fit was used to determine if there were significant effects on livelihoods. Results using satellite images showed that there were no significant changes in built up areas, agricultural land, bareland, grassland and shrubland during the period. It was however observed that the overall change of built up area, shrubland, bareland, agricultural land increased over the 26 years (1985-2011) period, while grassland decreased during the same period. Grasslands were therefore converted to build up areas, shrubland, bareland and agricultural areas during this period. An increase in built up area, bareland and agricultural land and a decrease in grassland are therefore likely drivers of gully erosion which is affecting the area. It was observed through PGIS that there were significant changes in shrubland which decreased in Eluai village and no significant changes in built up areas, bareland, agricultural land, waterbodies, xii grassland and shrubland in the three villages (Enkiloriti, Olepolos and Olesharo). PGIS therefore agrees with satellite images that a decrease in grassland was a driver of gully erosion in the study area. Results using the questionnaire showed that the effect of gully erosion on household activities differed significantly between the villages. This could be due to the fact that houses near the gully were the most affected by runoff. The effect of gully erosion on farming, livestock, level of income, water availability, firewood collection, building materials, health and mosquito breeding did not differ significantly between the four villages. This is because the effect on the mentioned livelihood activities was more or less the same in the 4 villages. There is urgent need to address gully erosion in order to safeguard community livelihoods and soil conservation in the catchment. A comprehensive land use plan needs to be developed in Suswa Catchment for effective rehabilitation of the gully and also reduce threats to livelihoods. Early warning signs of erosion particularly in highly prone areas should be emphasized. Community members also need capacity building particularly in the adoption of soil conservation measures in order to minimize the negative effects on their livelihoods