The impact of land cover change on runoff coefficient at Upper Garang Watershed, Jawa Tengah Province, Indonesia

Abstract

The Upper Garang Watershed serves as a vital water catchment area and supplier for the surrounding regions. Changes in land cover particularly the conversion of vegetated areas to built-up spaces or the reduction of high-density vegetation to low-density coverage can increase the runoff coefficient and disrupt the water supply. This research aims to analyze the impact of land cover change on the runoff coefficient in the Upper Garang Watershed. The data in this research was the topographic map of Indonesia (RBI), the Upper Garang Watershed map, the soil map, the river flow map, and Landsat imagery. The land cover changes in 2013 - 2023 were analyzed from Landsat imagery. The runoff was analyzed by calculating using Cook method based on mapping slope, soil infiltration, vegetation density, and river flow density. The results showed that in 2013 – 2023, vegetated areas of forest and agriculture decreased, however, plantation and settlement increased. Land cover changes from vegetated areas becoming built-up areas was about 28.36% of the Upper Garang Watershed area. Land cover changes affected the runoff coefficient. The runoff coefficient changes about 2%.