Jamil Tajam et al. 381 Distribution of Sediment Characteristic in Kilim River Estuary during the Non-Monsoon and Monsoon Season. Jamil, T. Norsila, D. Ashraf, A. ABSTRACT A study to determine the distribution of sediment pattern (mean, sorting and skewnes) was car- ried out in the Kilim River. The bottom sediment from 10 stations was collected. The mean grain –size ranged from 3.27 to 7.00 phi and 3.32 to 6.20 phi for the non-monsoon and monsoon sea- son respectively. The mean diameter indicates most of the sediment in the system consists of fine to very coarse silt, and mostly dominated by very poorly sorted for non-monsoon season (1.89±0.42 phi) and for monsoon season (2.04±0.34 phi). Skewness was symmetrical skewed for both season at the downstream area and these could probably be associated with sediments ero- sion in environments dominated by strong current actions (during tide or monsoon season) or due to the accumulation of coarser grains at these areas. Keywords: grain size, mean, river, seasonal variation, skewness, sorting Introduction The estuary sediments are usually derived from different mineralogical source (e.g. fluvial ori- gin, marine provenance and mixtures). It is often impossible to a single representative reference site for spatial comparison to detect an quantify anthropogenic pollution. Furthermore, sediment grain size characteristic and surface area measurements are of great importance to sedimentolo- gist, whose interest lies in soil characterization and trace elemental chemistry (Horowitz & El- rick, 1987). Size distributions provide good quantification for soil studies and carry information concerning the weathering phenomena about the transport, sorting, and sediment source (Krank & Miligan, 1985; Krank et. al., 1996a; Krank et. al., 1996b; Lang & Stevens, 1999) Analysis of grain size distribution has been widely used by sedimentologist to classify sedi- mentary environments and elucidate transport dynamics. The grain size of sediment provides an indication of the shear stress that must be applied by the medium to initiate and sustain particle movement. Grain size distribution is affected by other factors such as distance from the shore- line, distance from the source (river), source material, topography, transport mechanism and also seasonal changing. For many years, the size and distribution of the sediment were determined exclusively by using sieve analyses, and silt and clay fractions were determined by pipette or hydrometer methods. In early 20th century, many researchers and engineers shared their ideas to create latest methodology and technology in terms of determination of the grain size distribu- tion. These new method and technology are the most precise, fastest and yield highly reproduci- ble results compared to the classic method. However, the accuracy of these measurements is depending on the sampling techniques, storage conditions, analytical methods, equipment, and, especially, the capability of the operator. Furthermore, there is no ultimate technique or proce- dure that will produce the most desirable grain size data for all cases. Several types of analyses have been developed over the years to accommodate the different types and sizes of samples and the reasons for conducting the analysis In Malaysia, even though studies relating physicochemical and biology aspects of the main river are well documented (Kamaruzzaman, 1994), studies on bottom sedimentation are still quite limited. However, other sediment measurement techniques including those based on acoustic backscatter, remote sensing, Smart imaging technologies and digital photo-optic are many done by the local agencies (e.g.: Malaysian Institute for Nuclear Technology, Department of Irrigation and drainage and local universities). Nevertheless, detailed investigation concerning both spatial and temporal variability is required in order to better understand the sedimentation processes in the estuaries and along the Kilim River. In view of the importance of the bottom