EVALUASI PREDIKSI DEBIT RENCANA Qt BERDASAR PANJANG DATA HUJAN YANG BERBEDA

Abstract

Design flood based on Return Period reference (Qt) of a Hydraulics structure was calculated ten or more years ago, then calculating now with recently data ( with longer data at the same station), the result is difference. Cause of flooding- eg some structures are damage- usually recalculate is needed to know how much the actual discharge flows. The Author here will compare the result of discharge calculation based on return period between set of short data A: 14 years (1980-1993) with set of long data C: 27 years (1980-2006) at the same station, and also set of data B:13 years (1994-2006) with set of long data C:27 years (1980-2006) at the same station. The result is shown that with the same value of return period – eg Q5,Q10- calculated with set data A, B, and C respectively are difference. So, checking discharge isn’t recommended to return period (T) as reference, but its better use value of discharge (m3/sec) as reference. From the calculation above, the facts are: - Average of Rain fall set data, be influence to amount (much) of Qt, especially for short return period (t : small than 50 years) - Trend of set data, will be influence value Qt for longterm return period. Discharge calculation based on Rational Method, location of study : Tulis Weir, Banjarnegara. Keywords: Return Period, Rational.