Analisis Curah Hujan untuk Pendugaan Debit Puncak dengan Metode Rasional pada DAS Belumai dan DAS Bedagai

Abstract

The changes of land use at catchments area resulted in a significant impact on flood discharge. The impact of the change in the order of land use was the increase in the direct surface flow, at the same time, the decrease of water that penetrated in to the soil, and more run off as the river water discharge. If this river’s discharge is too high, and exceeded the capacity of the river, flood will happen. Realising the big impact that, caused by the climate anomaly, either in the form of flood or drought, the availability of data and quick climate information that accurate according to space and time were increasingly felt to be urgent for prediction and anticipation. In this case rainfall was calculated using frequency analysis, starting by determining the maximum mean daily rainfall with annual maximum series method, followed by calculating the statistical parameters to choose the best distribution. Rainfall data ware transformed to hours intensity rainfall with Monobe method to calculate the maximum flood discharge using rational method. Result of this research indicated that Log Pearson Type III distribution was fit to most data in the Belumai DAS and Bedagai DAS.