More developed means dangerous: spatial evidence of multi-decadal urbanising watershed and its impact to flash flood in metropolitan Semarang-Indonesia

Abstract

ABSTRACT This research conducts spatial verification of the watershed urbanisation phenomenon’s occurrence, which has implications for environmental problems and disasters. The evaluation employs a spatial analysis tool that incorporates variables such as changes in land cover, water run-off, flood risk, and stakeholders’ participation in watershed spatial planning. The study is supported by spatio-temporal data from remote sensing from 1970 to 2023, utilising various types of Landsat satellite imagery, including Landsat 5 TM, 7 ETM, and 8 OLI. The data is processed using GIS and several calculations assessing the impact of land cover changes on run-off discharge. The findings reveal significant differences in land cover in the upper area of the Garang Watershed-Metropolitan Semarang, Indonesia. This situation is exacerbated by overlapping interests in management, resulting in a watershed spatial plan that does not support land conservation efforts and prioritises the growth of upper-class settlements in the watershed area. These results demonstrate that the spatial policy in the Garang Watershed has yet to fully accommodate the interests of sustainable development, particularly in addressing the issue of watershed urbanisation.