Environmental Change Monitoring at Mwatate Watershed: A Local Scale Gully Erosion Mapping

Widespread concern about the state of the environment and the impacts of physical and human activities on the ecosystem has highlighted the need to identify the causes and map them at a scale in order to monitor the changes caused to the environment. Gully erosion in remains a critical concern worldwide. As a consequence of recent overgrazing, mining activities, farming, and deforestation, gully erosion at the Mwatate Watershed have become rampant. This research presents a methodological framework for mapping and analyzing the gully erosion at the Mwatate watershed utilizing GIS and Remote sensing techniques. For this purpose, vector datasets were used to quantify the local scale land cover change by analyzing the gully density (m/ha) change between the year 2004 and 2020. Gullies were detected by visual interpretation from georeferenced aerial images for both years and manually digitized as polylines in ArcGIS and vector grid-based GIS modelling techniques done on the gullies. Binary modelling in GIS was done to quantify the presence/absence of the gullies in the study area. In addition, LULC analysis was done to quantify the changes in the land cover mainly driving the gully erosion. It was observed that the gully density in the study area changed from 740 (m/ha) to 1200 (m/ha) between year 2004 to 2020. The LULC changes for the area also showed a reduction in the vegetation cover by 26 % and an increase in the buildup area by 34 % for the same period. The state of the environmental degradation from the gully erosion was mainly aggravated by human activities that have progressively increased in the area. This study, therefore, puts into perspective the need for environmental monitoring practices at a local scale and the need for the governing authorities to regulate the environmental degradation activities such as deforestation