TRANSACTIONS ON SCIENCE AND TECHNOLOGY Transactions on Science and Technology Vol. 4, No. 4, 442 - 448, 2017 Montoi et al., 2017. Transactions on Science and Technology. 4(4), 442 - 448 A Study on Tuaran River Channel Planform and the Effect of Sand Extraction on River Bed Sediments Jayawati Montoi 1# , Siti Rahayu Mohd. Hashim 2 , Sanudin Tahir 1 1 Geology Programme, Faculty of Science and Natural Resources, Universiti Malaysia Sabah, Jalan UMS, 88400 Kota Kinabalu, Sabah, MALAYSIA. 2 Mathematic With Economic Programme, Faculty of Science and Natural Resources, Universiti Malaysia Sabah, Jalan UMS, 88400 Kota Kinabalu, Sabah, MALAYSIA. # Corresponding author. E-Mail: jfshakim@gmail.com; Tel: +6088-260311; Fax: +6088-240150. ABSTRACT 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. KEYWORDS: River planform, Sand extraction, Bed sediment, River bank, Kruskall-Wallis test. Full Article - Earth and related Environmental sciences Received 8 October 2017 Revised 25 October 2017 Accepted 26 October 2017 Online 28 December 2017 © Transactions on Science and Technology 2017 INTRODUCTION River sand extraction is a removal process of sediment from river bed either using heavy machineries or suction dredges. Extraction activities in obtaining river sediment such as sand and gravel are very common nowadays due to rapid urban development and lacking alternative sediment sources (Kondolf, 1994; Rinaldi et al., 2005). Furthermore, river sediment has several advantages such as (a) the material is durable, rounded and well-sorted; (b) located near the markets or transportation routes, minimize the transportation costs; (c) channel sediment can be easily quarried so the extraction and processing of the material is relatively low cost and (d) it is a renewable resource through sediment transport processes (Kondolf, 1994). Sediment removal directly alters the channel geometry and bed elevation (Kondolf, 1997). Although it has a positive economic impact, this activity may also contribute to the negative changes in the river environment for either short or long periods. When the rate of sediment extraction exceeds the replenishment rate of these materials, it will eventually leads to many environmental issues (Kondolf, 1994; Padmalal et al., 2008; Ashraf et al., 2011). Excessive river sand extraction activities produces many kinds of physical effects such as impacts to infrastructures (Kondolf, 1997), channel instability eg. lateral changes, changes in channel width and morphology (Surian & Rinaldi,