Calibration of soil moisture accounting (SMA) parameters in Sungai Johor river basin using hydrologic model HEC-HMS

Abstract

Heavy rainfall on the 19th to 31st December 2006 and 12th to 17th January 2007 has caused two major floods within Sg. Johor River Basin. Global climate change had contributed to this unexpected event of extreme flood. The disaster caused a lot of damages and losses to the residents of Kota Tinggi. The second wave flood caused more severe than the first wave flood. It was predicted that soil moisture content might not be fully dry to sustain the second wave rainfall event. Less rainfall was absorbed and high surface runoff was generated. The infiltration rate is directly proportional to soil moisture content. There is high possibility that the soil moisture content might influence the result of these two flood events. Nowadays, the application of computer modeling has become the best alternative in solving engineering problems. Therefore, HEC-HMS 3.3 model was used in this study to estimate the peak flow in Sungai Johor River Basin. Precipitation and discharge data were acquired from Department of Irrigation and Drainage (DID). Simulation on long term rainfall event in Sungai Johor River Basin was analyzed using Soil Moisture Accounting (SMA) method in HEC-HMS computer model. The reliability of eighteen SMA parameters has been identified in order to estimate flow for the next rainfall event. The model parameters were calibrated using the data recorded on 1st September 2002 to 29th May 2003. The rainfall data was taken from rainfall station located at Bukit Besar and Ulu Remis, while the discharge data was observed at Rantau Panjang stream flow station. The calibration result shows good correlation between the simulated peak discharge (139m3/s) and the observed peak discharge (140m3/s). However, for validation process, the result shows 25 % difference between the observed (195m3/s) and the simulated peak flow (165m3/s), The validation process uses data that was recorded from 1st August 2005 to 22nd April 2006. The rainfall data was taken from three stations Bukit Besar, Ulu Sebol and Ulu Remis.