The comparison of rainfall intensity analysis methods in upstream area of Belik Watershed, Yogyakarta

Abstract

Belik Watershed is one of a catchment which located in urbanized area of Yogyakarta. The upper stream part of this watershed have very important role as recharge area. However, vast land conversion occurrence in Sleman Regency threatened its function and cause several inundation case within the area. In other words, stream capacity unable to accommodate the surface runoff. This research intend to analyzed rainfall return period and compare rainfall intensity analysis methods to be implement in the research area. Furthermore, statistical analysis performed to carry out suitable method in the previous research aims. The comparison of rainfall intensity analysis in the short time series distance utilizes Talbot Method and Sherman Method. Rainfall data of short times series distance obtained from Automatic Water Rainfall (ARR). This Calculations of the standard deviatiornesearch analyse 2, 5, 10, 25 and 50 years of return period. Calculations of the standard deviation and error square mean root peak-weight (PWRMSE) determine to choose which method has a better result. The design of rainfall intensity result shown in the Intensity-Duration-Frequency (IDF) graph. Based on the calculation, the most appropriate method is the Sherman Method with standard deviation and PWRMSE for each return period in chronological order of 2 years (-0.27) (Z 3.52); 5 years (-0.67) (Z 3.83); 10 years (0.3) (Z 5.39); 25 years (0.6) (Z 7.56); and 50 years (-1.0) (Z 9.72).