Runoff Volume Simulation Ciujung Watershed to Outlet Discharge (Case Study: Various Vegetation Cover Conditions and Precipitation)

摘要

Landuse change and precipitation can affect runoff volume associated with the discharge outlet of a watershed. Large volume of runoff makes environmental issues associated with runoff which is the impacts to surface water, especially floods. Ciujung watershed is a watershed in the Province of Banten, Indonesian, that categorized as critical watershed with frequent flooding in the area around the outlet stream. The objective of this research was to simulate runoff volume in Ciujung watershed in various vegetation cover and precipitation to calculate quantities of runoff, primarily for flood forecasting. The method used was rational method whereby the discharge of runoff (Q) was precipitation volume per unit time which didn't undergo infiltration so that it had to be flowed through drainage channel. Measurement of physical characteristic data of Ciujung Watershed included wathershed morphometry, flow density, soil infiltration, and vegetation. The data were obtained from remote sensing data with thematic maps and data from the agency. The result was that the precipitation which fell in Ciujung Watershed approximately 50% to be runoff, by the simulation that watershed with 90% vegetation cover, affected runoff by 15%. Therefore, various vegetation cover was inversely proportional with the runoff volume and the runoff volume was proportional with the main river discharge outlet. The results also showed that design rainfall was the most influential factor to the increasing trend in main river discharge outlet.