The Impact of Land Use Change on Surface Runoff at Air Dingin Sub-watershed, Padang City Indonesia

Abstract

The land load in the Air Dingin Sub-watershed is increasing due to the relocation of the Padang City administrative center to the district. Subsequently, this not only reduces the catchment area but also increases the surface runoff, because the open green space, which originally served as a catchment area, has been converted into settlements. A random measurement of the infiltration rate with a double-ring infiltrometer was used as a method and analyzed using the Kostiakov technique. The infiltration capacity obtained is then classified quantitatively into infiltration zoning. The runoff discharge was analyzed using Modeling System of hydrology, while the flow coefficient was determined by analyzing topography, land use, and soil type data with HEC-HMS modeling, the HSS SCS CN Method and ArcGIS 10.6. The Kostiakov method is used to calculate the capacity value in field filtration. This method took into account the physical properties of the soil and land cover. The performed analysis showed that the runoff discharge was 788.70 m3/sec, while the design discharge (2010) was 600.0 m3/sec. The runoff discharge increased by 188.70 m3/sec or an increase of 31.45%. The average infiltration rate in this area was 0.000002-0.5 cm/minute, and there was a residual discharge after the infiltration and percolation process of 499.31 m3/second. This residual discharge caused flooding in Air Dingin Sub-watershed with an initial inundation of 5.72 minutes after the rain. In terms of zoning division of the catchment area based on the value of the infiltration rate, the Air Dingin Sub-watershed area is in a very low infiltration rate zone.