FLOOD ROUTING ANALYSIS OF THE WAY SEPUTIH RIVER, CENTRAL LAMPUNG, INDONESIA

Abstract

Lampung is currently vulnerable to flooding. There were 16 flood events in Lampung with the
latest major flood, which occurred in February 2018, inundated 10 sub-districts. One of the main causes of
flooding in Lampung is flash flooding caused by heavy rainfall on the upstream area. The villages along Way
Seputih (Seputih River), one of the main rivers in Lampung, Indonesia, have been affected by flash flood for
the last three years. One of the possible solutions to control the flood from causing heavy causalities is to create
a flood route model of Way Seputih, which is the main focus of this study. In this study, a hydraulic model of
Way Seputih is built by using HEC-RAS 4.1 software to simulate the effect of extreme rainfall and how it
causes flooding along the Way Seputih. The hydraulic model is based on field topographic measurement,
simulated tides, and synthetic hydrographs generated by rainfall data and validated by field water surface
elevation measurement. The output of HEC-RAS 4.1 in form of water surface elevation time series of locations
along the Way Seputih is then used to build a flood route model. By using this model, the flooding time interval
between villages along the Way Seputih can be predicted which can be used as the basis for an early warning
system or planning for flood defense infrastructures such as dikes and pump systems.