Abstract:
Soil erosion causes sediments to be detached from their source materials and
transported as suspended particles. The present study was conducted to evaluate the
effects of sand exploitation on the distribution of suspended sediments in the Educational
and Research Forest Watershed of Tarbiat Modares University, which comprises
approximately 50,000 ha. Fifty-one water samples were collected before and after sand
mining between November 2007 and June 2008. The settling rates of the primary particles
of suspended sediments were then analyzed based on the principle of sedimentation
described by Stokes’ law and using the modified pipette technique. Analyses of the
samples indicated that the Suspended Sediment Particle Size Distribution (SSPSD) was
significantly affected by sand mining. Specifically, an independent samples T-test
demonstrated that the mean contents of sand, silt and SSC during and after sand mining
differed significantly (P< 0.01), with respective values of 74.19±13.4 and 9.75±13.8,
81.77±4.5 and 2.96±2.7% and, 7.66±7.7 and 0.34±0.3 g l-1 being observed. Additionally, no
significant difference was found between data sets collected before and during sand
mining for hydrologic and SSPSD characteristics at 1%, which clearly proved consequent
effects of sand mining on SSPSD.
Keywords: Kojour watershed, Particle size distribution, Sand mining, Suspended sediment
concentration.
