Physiographic Study for Hydrology of Embung Hendrosari Region, Gresik Regency

This study aims to determine physiographic characteristics based on the slope and land use which affect water control in Embung Hendrosari area, Gresik. The data used in this study are DEM data, Landsat 8 image data, and river data. The slope data processing is carried out through slope classification analysis. The Landsat 8 data processing is used for land use classification analysis. The slope classification maps and land use classification maps are used to classify flow coefficients. There are five land classifications obtained in land cover classification map including agriculture, settlements, industrial areas, plantations, and waters. There are 5 classifications obtained on the slope classification map, including flat, sloping, slightly steep, steep and very steep. The flow coefficient analysis is performed from the combination of land use data and slope data. The flow coefficient is influenced by the characteristics of the land cover and the slope of the slope. The average flow coefficient of Embung Hendrosari area is 0.31, which classified as medium flow coefficient. This indicates that 31% of the water is run off on the ground surface and 69% of the water is absorbed below the soil surface. There are changes in land function in Embung Hendrosari area, for example, agriculture area which changed into settlement and/or industry, which will significantly affect the value of the flow coefficient. The change in land use causes more water to run off the surface. This runoff water management requires a water reservoir that can be directed toward reservoir. The results of this study show such an initial step in hydrological engineering by its development, improvement, utilization, and control of water flow by utilizing the function of Hendrosari Gresik reservoir.