OPTIMAL SAND REMOVAL CAPACITY FOR IN-STREAM MINING IN PERAK RIVER, MALAYSIA

New or alternative source of sands need to be determined due to the increasing demand for sand by construction industry. Floodplain and river bars can be used as new sources of sand mining. This method however is still new in Malaysia. This study was carried out to estimate the sand capacity at floodplain and river island by combining the resistivity method and sediment transport load. By using resistivity survey, the thickness of subsurface can be determined easily and it can also measure large area simultaneously. Hence, this method is able to find new source of sand at floodplain without disturbing any groundwater sources. In Sungai Perak, many river islands and river bars could be new source of sand mining. Nowadays, unpredictable weather can cause high precipitation, flash flood and also drought. The high precipitation can cause high flow in river. This high flow can cause deflected flows by river island which can cause riverbank erosion which leads to instability of river. Therefore, river erosion can probably be reduced by using this technique. Study found that the high replenishment rate of Sungai Perak which is approximately 1245.43 m 3 /day can cover back the river bed about six days if 2.0 meter extraction is conducted on this river island A. For river island B, the replenishment period is about 98 days for 2.0 meter extractions.