Determining spatial variability of penetration resistance and particle size distribution in sediment deposition
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Erosion and sedimentation in dam reservoirs may result in both ecological and economic problems. That is why, besides its amount, it is important to know physical and chemical properties of sediment accumulated in reservoirs. Thus, it is possible to gather information regarding erosion and parameters affecting the erosion process in a watershed. Determining particle size distribution generally comes first when investigating physical properties of sediments. Despite similar texture formation, compaction degree of sediment layers increases due to repacking of particles with time. It is important to figure out compaction degree of sediment layers in accumulation sites and measuring penetration resistance is one of the techniques used mostly. This study was initiated in one of 9 sediment deposition sites determined along the Borcka Reservoir. Precipitation periods within the watershed of the reservoir and power generation cycles of the dam play an important role on the formation of these sedimentation sites. At the first stage of the study, lateral profile distribution and depth of sediment deposition were determined. Then, on sampling points, arranged by the grid system, penetration resistance was measured. In addition, disturbed sediment samples taken from the same sampling points at two depths (0-10 cm and 10-20 cm) were analyzed for moisture and particle size distribution. Geostatistical analyses were used on these values in order to produce spatial variation maps while regression was used to assess relationships between parameters investigated in this study. Results indicated that there were significant differences between layers in respect to penetration resistance values and particle size of sediments and it was found out that spatial variation of penetration resistance closely related with particle size distribution.