Infiltration Zonation Using Kostiakov Methods in Leftbank Jatigede District Indonesia
West Java Province is one of the vulnerable areas for having land movements in Indonesia. Sumedang Regency, the research area, has a varying level of soil movement, from low to high. Administratively it is located in the Eretan and surrounding areas, Jatigede District, Sumedang Regency, West Java Province. Based on the geological conditions and the engineering materials, the research area was divided into six engineering geological units, soft weathered rock units (SW), medium weathered rock units (MW), high weathered rock units (HW), sand gravel - perfect gravel units (CW), residual soil units (XW), and alluvial sediment units. Infiltration analysis can be carried out using an infiltrometer double ring and measurement and calculation. The study was aimed to determine the infrazation zone in each lithology in the study area. The data were analyzed by the infiltration method using the Kostiakov equation to obtain the final infiltration rate in the study area. The results showed that the infiltration rates at the surface of the ground were diverse, the infiltration zone of the tuffaceous breccia group at 0.0287 - 0.8375 cm/minute, the infiltration zone of claystone group, at 0.2754 - 0.6315 cm/minute and absorption zone the volcanic breccia group of sandstone inserts was 0.0852 - 0.2482 cm/minute. The final infiltration rate (f) was very diverse, from the lowest of 0.0852 cm/minute (5.11 cm/hour) to the highest 0.8375 cm/minute (50.25 cm/hour). The value could be used as a reference to determine the level of water saturation on the ground and the ability of the soil for passing the water.