Analisis Hidrologi dan Hidrolika pada Saluran Drainase Ramanuju Hilir Kotabumi (Menggunakan Program HEC-RAS)

Abstract

The calculation is done using the rainfall data obtained from BMKG Kotabumi North Lampung,
from 1998 until 2011 with time increment in minutes. The Log Pearson III method is used to find
the design rainfall with return period 2 years, 5 years and 10 years. Then the result is
implemented in the Intensity-duration-frequency (IDF) curves. Time of concentration is linked into
the IDF curves to determine rainfall intensity. Based on the calculated rainfall intensity, the
design discharge for each return period can be calculated using the rational method.
The values of design discharge are then inputted as upstream boundary condition in HEC-RAS.
Model output are presented in cross and long section to determine at which return period the
drainage capacity is overflowed. Simulation using HEC-RAS were also done to determine the
channel capacity.
Based on the results of this research, it can be concluded that rainfall intensities are 52,6918
mm/hour, 65,7820 mm/hour and 75,9032 mm/hour, for 2, 5, an 10 year return period respectively.
The capacity of the drainage channel is 2.02 m 3 /hour and is expected to be exceeded on 5 years
return period.
Key words : Intensity, Rasioanal method, HEC-RAS, capacity