Mapping and Analysis of Landcover Changes in the Upper Gucha Catchment using GIS and Remote Sensing

Abstract

Geospatial technologies and their capability to capture, store, manipulate and display data, have found great utility in the analyses of any geospatial phenomena with speed and accuracy anywhere on/above or below the Earth surface. One such field of application is watershed conservation and management. This study demonstrates the role of spatial technologies especially GIS (Geospatial Information Systems) and Remote Sensing, in the identification and analysis of human impact on the land cover through land use practices within the upper Gucha watershed. The upper part of the Gucha River has been harnessed for water supply development in Kisii and Nyamira towns and recently Keroka Township. It has a population growth rate of 2.75% per annum, poverty level of 51% and average population density of 874.7
persons per km2 leading to land fragmentation and clearing of primary vegetation within the catchment to accommodate the population. The methodology involved delineating the catchment using GIS Hydrology tools, by filling the DEM (Digital Elevation Model) and creating a flow direction, from which a flow accumulation was calculated so as to identify water pour points accurately for watershed delineation and channel generation. Preparation and processing of the satellite imageries for the years 1990, 2000 and 2013, was carried out in Erdas Imagine environment for onward change detection analysis. Results include Change Detection Maps of the watershed for visualization and quantification of land cover changes within the watershed over that period as tools for informed decision making by managers during conservation and management of the watershed. Some of the change detection analysis indicates that more forest land grassland is rapidly changing for crop land. The changes for forest land and grass land are 10.5% and 2.6% respectively for the period the study. Notably, 0.085% of the land changed from water bodies to forest land while the change from forest land to water bodies is 0.061%. A number of similar analyses have been presented. This study concludes by appreciating the importance of spatial technologies in not only mapping water
resources especially water channels in a watershed, but also in land cover/land use change detections for general management of resources.