The Impact of Land Cover Changes on Flood Hydrograph Characteristics (Jragung dam Case Study)

Abstract

Demak and Grobogan Regency are areas where a flood frequently happen during the rainy season. PUPR Ministry built the Jragung Dam for flood management which was planned using the 1998 - 2017 data series. The Jragung River discharge tends to experience an increase in a period of 10 years, with one possible cause is changes in land cover. Therefore, to determine the effect of land cover changes on the flood hydrograph characteristics of Jragung Reservoir, a flood tracking analysis was carried out in Jragung Reservoir. This study use the HEC-HMS program with the Soil Conservation Service (SCS - CN) method. and the land cover change index used was curve number and impervious. The results of the analysis show that there is a change in land cover in the Jragung Reservoir catchment area of 2,5%, which is dominated by an increase in residential area of 55,6%. As a result of conducted, the Jragung Reservoir catchment all n-year return periods flood discharge has increased from design year (2017) and latest year (2022). QPMF increased from 1586,1 m3/s to 1689,6 m3/s which resulted in an increase in the Jragung Reservoir flood water level from planned QPMF in +118,6 m become +118,7 m.