Analisis Curah Hujan untuk Pendugaan Debit Puncak dengan Metode Rasional pada Das Wampu Kabupaten Langkat

Abstract

Rainfall is the most important input component in the hydrologic process. Some of rainfall characteristics, are intensity (I), duration (t), depth (d) and frequency. Intensity that is related to duration and frequency can be expressed by Intensity-Duration-Frequency (IDF) curve. Data used in this research comprised of rainfall, land use data and catchment characteristics data. The data of rainfall used were daily rainfall recorded in Tanjung Jati station, Kwala Bingai station, Sawit Langkat station and Kwala Madu station. In the research, daily rainfall depth was calculated by frequency analysis, which was started by determining the daily maximum mean rainfall with Thiessen Polygons method to got thiessen coefficient. The daily maximum mean rainfall was used in calculating the statistical parameter to choose the best distribution in Wampu Catchment. Intensity could be calculated by Mononobe method based on return period. The result found in Wampu catchment was the Log Pearson Type III distribution. Multiplication among run off coefficient, rainfall intensity and all the flow width were used to get flood discharge with the rational method.