Upstream Watershed Degradation and Increased Risk of Flash Floods Amid Climate Change

Asikin Muchtar

doi:10.55927/fjst.v5i3.27

Authors

Asikin Muchtar Universitas Indonesia Timur

DOI:

https://doi.org/10.55927/fjst.v5i3.27

Keywords:

Jeneberang Watershed, Upstream Degradation, Flash Flood, Climate Change, Spatial Analysis, Disaster Risk.

Abstract

Land cover change in the upstream area of the Jeneberang Watershed, South Sulawesi, has altered river hydrological dynamics and amplified the impacts of increasingly intense extreme rainfall associated with climate change, thereby elevating the risk of flash floods in downstream regions. This study aims to examine the relationship between upstream watershed degradation, trends in extreme rainfall, and the escalation of flash flood risk through an integrated spatial–temporal analysis. A quantitative approach was employed using secondary data, including multitemporal satellite imagery from 2003–2023, 20 years of daily rainfall records, documented flood events, and population data. The analysis involved land cover classification and change detection using GIS, trend testing of extreme rainfall with the Mann–Kendall method, estimation of runoff coefficients and peak discharge, and risk modeling based on the Hazard–Vulnerability–Exposure framework. The results indicate a 17.8% decline in forest cover in the upstream area, associated with a 19% increase in the runoff coefficient and a 24% rise in estimated peak discharge during high-intensity rainfall events. Maximum daily rainfall intensity also shows a statistically significant upward trend (p<0.05). Risk mapping reveals a 29% expansion of high-risk zones, particularly in densely populated downstream areas. These findings demonstrate that the interaction between land use change and intensifying extreme rainfall exacerbates watershed hydrological vulnerability, providing a scientific basis for upstream restoration policies and ecosystem-based climate change adaptation strategies in the Jeneberang Watershed

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