Analisis Hidrograf Satuan Terukur Sub DAS Way Besai

Mega Astriyana, Dyah Indriana Kusumaastuti, Ofik Taufiq Purwadi


Way Besai River is the largest river in west lampung district. High sedimentation in this river
affects the performance of Hydroelectic Power Plant (HEPP) owned by PLN which is located in
Way Besai River. In order to know the condition of Way Besay’s catchment area, a research is
conducted on each of Way Besai’s sub catchment area. One of the sub catchment area is located in
Talang Bandung Village, Pekon Sindang Pagar, Kel Tugu Sari Kec Sumber Jaya West Lampung
District named Talang Bandung Catchment and Air Anak Catchment. In order to make the survey
of Catchments condition easier, the research uses measured unit hydograph analysis method. The
purpose is to analyse the measured unit hydograph in order to get the value of Peak Discharge,
Peak time, basic time, and analysing the flood hydrograph.
In this researc the data needed are automatic rainfall data, automatic water level data, velocity
data, and the stream cross section. From these data will be used to make Rating Curve to turn the
hydrograph of water level into flow hydrograph. The separation of the components of base flow
and direct runoff using straight-line approach and calculate the efective rainfal to get the ordinate
of unit hydrograph. From the average of unit hydrograph combined with periodic rainfall will
obtain the periodic flood hydrograph.
From the analysis result it is, obtained an average of hydrograph unit for each catchment area. On
60 minutes period, the average of unit hydrograph of Air Anak Catchment and Talang Bandung
Catchment have average peak discharge average (Qp) of 0,340 m 3 /sec and 0,394 m 3 /sec, the time
of rise are 560 minutes and 660 minutes. The result shows that for return period of 25 years, flood
discharge for Air Anak is 16,832 m 3 /sec and for Talang Bandung is 20,179 m 3 /sec.
Keywords: Measured Unit Hydrograph Analysis, Sub Catchment Area of Way Besai.

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ISSN: 2303-0011