Two-Dimensional Simulation Of Upper Sungai Langat Using HEC-HMS, HEC-RAS And RRI Model
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Date
2019-08-01
Authors
Mohamad Faudzi, Siti Multazimah
Journal Title
Journal ISSN
Volume Title
Publisher
Universiti Sains Malaysia
Abstract
Flood is one of the natural disasters occurring in Malaysia. Floods usually occur due
to the overflow of water from the riverbanks which inundates the surrounding area.
Hulu Langat district, located in Selangor was severely affected by floods. Sungai
Langat is the main river flowing from Banjaran Titiwangsa into the Strait of Malacca
with a length of approximately 141 km. The study area is focused on the upper
Sungai Langat basin area where main cities such as Kajang, Bangi, Seri Kembangan
and Dengkil are situated. These cities which are located at the downstream area of
upper Sungai Langat were frequently inundated during heavy rainfall events. This
scenario had caused a nuisance to the surrounding people of the inundated areas.
Thus, HEC-HMS, HEC-RAS and RRI models were used to simulate the rainfall-runoff
occurrences in the upper Sungai Langat basin. The objectives of this study are
to (a) simulate the flood inundation in upper Sungai Langat using HEC-HMS and
RRI models; (b) compare the results of HEC-HMS and RRI models based on
discharge values and; (c) produce flood maps using HEC-RAS and RRI models. The
rainfall and discharge data which were used as the input data for HEC-HMS and RRI
models were provided by the DID. DEM data of 1 arc-second and 30 arc-second
resolutions were used in the HEC-RAS and RRI models respectively. Simulation of
five rainfall events using HEC-HMS and RRI model were conducted to calibrate
particular parameters. The calibrated parameters were used to validate three rainfall
events using HEC-HMS and RRI models. The graphs of observed versus simulated
discharges were plotted to find the correlations between both data using the
correlation coefficient, 𝑅². All plotted graphs showed that the range of 𝑅² values was
between 0.5 - 1.0. (0.3 - 0.7 = moderate; 0.7 - 1.0 = strong). Overall, the data were
found correlated to each other. Flood maps were generated using the HEC-RAS and
RRI models based on the simulated discharge data. Based on the maps produced by
the HEC-RAS model, highest precipitation and discharge of 11.5 mm and 132 m³/s
respectively had inundated some areas in Kajang. Inundation maps produced by the
HEC-RAS model were clearer and easy to understand compared to the maps from
RRI model due to low resolution of the DEM. Thus, the simulation of rainfall-runoff
using HEC-HMS and HEC-RAS models is found more practical.