Assessment of Flood Discharge Variability Due to Land Use Changes in the Konto River Basin with HSS Nakayasu and HEC-HMS Modelling

¹ Departement of Civil Engineering, Universitas Islam Malang, Malang, East Java, Indonesia
² Faculty of Civil Engineering, Universiti Teknologi MARA, 40450 Shah Alam, Selangor Darul Ehsan, Malaysia

Abstract

Flood disasters in watershed regions are highly influenced by changes in land use, which directly affect the hydrological response of a basin. This study assessed the variability of flood discharge in the Konto River Basin, Malang Regency, under different land use conditions using the HSS Nakayasu method and HEC-HMS hydrological modelling. Land use data from multiple years were analyzed to identify conversion patterns from forested and agricultural areas into settlements and other uses. These changes were incorporated into hydrological parameters to simulate peak discharge and runoff characteristics. The results show that land use change significantly increased peak flood discharge and reduced the natural retention capacity of the watershed. The HSS Nakayasu method provided an empirical estimation of hydrograph response, while HEC-HMS simulations offered a more detailed analysis of rainfall-runoff processes. Both methods confirmed a rising trend in flood discharge associated with land conversion, with HEC-HMS yielding higher accuracy in reflecting observed hydrological conditions. This research highlights the critical role of sustainable land use planning in mitigating flood risks and provides valuable insights for watershed management strategies.