A study on tuaran river channel planform and the effect of sand extraction on river bed sediments

River sand extraction is known as one of the main factors that induces the significant changes on river planform. This paper main objective is to study on the significance of planform changes on Tuaran River from 2003 to 2016 and sediment composition changes due to this activity. The study on channel planform focuses on four single wavelength channel bends which are located at the downstream of Tuaran River. Two meander features which are the channel width (w) and radius of curvature (Rc) were measured from digitized Google Earth satellite image year 2003, 2013, 2014 and 2016 and overlay with the Department of Survey and Mapping Malaysia (JUPEM) topographic map using Geographic Information System (GIS) software and georeferenced to World Geodetic System (WGS) 1984. Four sites which are located at the downstream of Tuaran River were selected to determine the river bed sediments composition. Three of the four sites are located at the sand extraction area whilst one site is a controlled area with no sand extraction activity. River bed sediments were collected and the sediments composition was analyzed using Mann Whitney and Kruskal-Wallis tests to determine the composition difference between the areas and the inner parts of the river. The analyses result showed that the pattern of channel planform changed throughout the years except between 2013 and 2014. Sand extraction activity altered river planform at a faster rate than normal river process where the reduction width of the river in this extraction area is significantly larger. Mann Whitney test on the river bed sediment shows that sediment composition is significantly differed with respect to the areas. Meanwhile, the Kruskal Wallis test showed that the area with no sand extraction has a significant difference in particles mean size between the outer bank, inner bank and middle part of the river unlike the area with active sand extraction. These findings proved that sand extraction activity has changed the river bed sediments distribution in extent changing the channel planform of the Tuaran River