Analysis of classification hydrologic soil group distribution based on infiltration rate of horton method in the upper Ciliwung watershed

Runoff coefficient or Curve Number (CN) is a parameter value needed to describe runoff in accordance with the intended land use. In determining CN values, it is necessary to take account the Hydrologic Soil Group. The Hydrologic Soil Group (HSG) consists of 4 groups, which are: A, B, C, and D. In order to classify the appropriate HSG, several methods can be used, namely: soil properties, soil maps, or minimum infiltration rates. In this research, an HSG classification distribution analysis will be carried out based on the infiltration rate obtained from actual conditions found during observation in the research site. This research was conducted in 13 locations, situated in the Upper Ciliwung watershed. The division of 13 locations is based on the distribution map of the HSG according to the Geological Information Agency and also the map of the distribution of Upper Ciliwung sub-bases. In its classification, each HSG has a different infiltration rate value. In this study, an analysis of the distribution of HSG classification based on the infiltration rate was obtained from direct observation on the research site. The study was conducted using a double-ring infiltrometer. The data obtained from the study were then processed using parameter estimation and the Horton Method to obtain the Horton infiltration rate. When the infiltration rate value is known, the corresponding HSG can then be determined for the soil at that particular location. With Inverse Distance Weighted in ArcMap, a map of the spread of infiltration rate and classification of HSG will be obtained in the Upper Ciliwung watershed. The infiltration rate obtained in the Upper Ciliwung watershed ranges from 0.15-12.6 cm/hour. The distribution of HSG is also found in the Upper Ciliwung watershed, consisting of groups A, B, and C.