Simulation of Muda River Channel Changes due to Sand Mining Operations 

Natural river is a form of channel that easily changes in term of its physical shape such as width or depth as well as the changes in water pollution. Unplanned development couples with human and natural factors are the biggest contributors to changes in the river equilibrium. Economics activities such as agricultures, urbanisation, fishery, sand mining, etc, should be control in ensuring the balance of river eco-system. Sand mining activities are usually concentrated at the sandy-bed natural rivers. River sands are an important element in development factors, where its demand increases linearly with Malaysian infrastructure development.  

The research was conducted to identify the changes of riverbed due to sand mining activities at Muda River in Kedah because of currently active sand mining operations along the river. This research consists of river cross-sectional survey, sediments sampling and water level records at seven stations along a 5 km river reach.

 The extensive sand mining activities along the research area requires closed supervision and control by related authority in ensuring that erosions are minimised. The mining depth needs to be closely monitored so that sand miners do not exceed the permitted depth of Sand Mining Guideline established by Jabatan Pengairan dan Saliran Malaysia (JPS). Based on survey works that have been carried out in year 2001 and 2002, it has been found out that the sand miners have failed to fulfil the requirements of the Sand Mining Guideline given by JPS. Almost all the cross-section within the research area having width more than 50 m, have been mined exceeding 1.5 m depth of the allowable tolerance.

A mathematical model, FLUVIAL-12 (Mathematical Model for Erodible Channel, Chang, 1988) was used to forecast the changes of Muda riverbed. The calibration carried out shows that the Manning Coefficient, n = 0.040 is suitable for Muda River analysis. Yang Equation also gives almost an accurate result to the actual condition at research site. Selected simulation cases have successfully shown that the changes of riverbed are due to sand mining activities and flood. The results also show that the past flooding (1988, 1998) have given major effect to physical stability of the research area compared to sand mining activities.