APPLICATION OF A RAINFALL-RUNOFF MODEL FOR ASSESSING THE EFFECT OF LAND USE CHANGE ON FLOOD CHARACTERISTICS IN SERANG REGENCY, BANTEN

I A Rakhmatika^[1]*

¹Universitas Gadjah Mada

[1]^* Corresponding author’s email: [email protected]

DOI: https://doi.org/10.20885/icsbe.vol4.art33

ABSTRACT

A flood in Serang Regency is predicted to occur due to changes in land use in the Ciujung River Basin. Land cover conditions in upstream areas affect flooding in downstream areas. A study is needed to evaluate the runoff from the Ciujung River Basin that reaches the flood-prone area in Serang Regency. This research aims to identify the effect of land-use change on floods in the Serang Regency and identify sub-watersheds that have a dominant influence on floods. The effect of the land-use change was analyzed by determining the composite curve number (CN) values in 2010 and 2019. Composite CN values were used for simulating flood hydrographs with 5, 20, 50, 100, and 1000 return periods using a simple semi-distributed rainfall-runoff hydrological model. The results showed that all sub-watersheds experienced an increase in composite CN values. The upper middle sub-watershed has a dominant influence on floods in normal conditions ranging from 9.2%-19.6%, in wet conditions ranging from 2.4%-6.5%. Implementing the spatial pattern of the Banten Provincial Plan 2010-2030 can reduce the composite CN value and the peak discharge of flood by around 7.3%-13.3% for normal conditions, in wet conditions down by about 1.7%-4.1% for each return period.

Keywords: Flood; Hydrological Model; Effect of Landuse

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