JWSS - Journal of Water and Soil Science

Spectral Reflectance of suspended sediment concentration (SSC) remotely sensed by satellite images is an alternative and economically efficient method to measure SSC in inland waters such as rivers and lakes, coastal waters, and oceans. This paper retrieved SSC from satellite remote sensing imagery using radial basis function networks (RBF). In-situ measurement of SSC, water flow data, as well as MODIS band 1 and band ratio of band 2 to 1 were the inputs of the RBF. A multi-regression method was also used to make a relationship between the in-situ data and the water reflectance data retrieved from MODIS bands. The results showed that RBF had the best SSC prediction error (RMSE=0.19), as compared to the multi-regression and sediment rating curve methods, with the RMSE of 0.29 and 0.21, respectively.

Few studies have been done regarding the role of the raindrop in the hydrodinamic mechanism of soil erosion. In this study, rainfall simulation experiments were conducted to evaluate the role of raindrop in runoff discharge, sediment concentration and hydraulic properties of flow under four slope gradients (5, 10, 15 and 20%) in a clay soil using a 90 mm.h^-1 rainfall intensity to reach the steady state flow. Soil sample was packed into the erosion flume with 0.3m× 0.4m × 4 m in dimensions and tested under two soil surface conditions:  one with raindrop impact and one without raindrop impact. The results showed that runoff discharge, sediment concentration, flow depth, shear stress, stream power, Reynolds number and runoff velocity under without raindrop impact condition were significantly lower than those in the condition  with the raindrop impact with a factor of 0.62 to 3.54, 0.08 to 11.83, 0.91 to 0.96, 0.26 to 3.25, 0.52 to 4.45, and 0.36 to 3.27, 0.23 to 0.79 times, respectively; on the other hand, the Darcy Wysbach, Chezy and Manning coefficients were increased significantly under without raindrop impact (P<0.01). Flow velocity was the key hydraulic parameter strongly affecting the hydraulic properties. These findings indicated the importance of raindrop impact in the detachment rate of soil particles through the change of the hydraulic characteristics. This study also revealed the key role of raindrop impact on the runoff hydraulic characteristics, as well as particle detachments rate in rills. Information about the role of raindrop impact is a substantial step in modeling the rill erosion. Therefore, elimination of raindrops impact, especially in the steep slopes, with the conservation of natural vegetation cover can sufficiently prevent runoff production as well as the particle detachment rate.

Soil erosion is one of the most serious environmental issues in the world, causing soil degradation, reduction of land productivity, increasing flood, water pollution and pollutions transportation; it is also a serious threat to sustainable development in the world. Therefore, the soil conservation and the prevention of soil erosion and use of conditioners as the nanoclay can be considered as a solution to improve   land productivity and protect environment. The present study was, therefore, conducted to address the effect of the application of montmorillonite nanoclay with three rates of 0.03, 0.06 and 0.09 t ha^-1 on changing runoff and soil loss variables under laboratory conditions. The results showed that the nanoclay with the rate of 0.03 t ha^-1 could decrease the runoff coefficient, soil loss and sediment concentration with the rate of 40.65, 88.38 and 82.19 percent, respectively. The average of soil loss in control treatment and conservation treatments of nanoclay with various rates was measured to be 3.76, 0.44, 1.33 and 3.16 g, respectively. Also, the results showed that the most sediment concentration was the control treatment with the rate of 5.84 g l^-1 and the conservation treatments with nanoclay in the applied rates was 1.04, 3.47 and 2.96 g l^-1, respectively. Also, the results showed that the nanoclay effect was significant on changing the soil loss and sediment concentration at the level of 99 percent. Finally, due to the effect, the use of this conditioner in natural conditions and investigation of the effects on environment and aggregates stability are recommended.

Soil loss can cause many intra-regional and extra-regional problems, on the other hand, the effect of soil moisture on processes of soil loss and sediment yield for the identification and simulation of soil hydrological response is necessary. Therefore, the application of soil conditioners is essential for soil and water conservation. The present study was conducted to investigate the effect of soil conditioners of vermicompost and nano-manure on variables of soil loss and sediment concentration at moistures of air-dried, 15 and 30%, and rainfall intensities of 50 and 90 mm h^-1. The obtained results in addition to confirmation of the significant effect of each conservation treatment at the level of 99 percent on the intended components showed that the conservation treatment of vermicompost compared to nano-manure treatment had more effect on measured variables. Also, the conservation treatment of vermicompost could decrease the soil loss at soil moisture air-dried, 15, and 30 percent with rates of 72.15, 66.63, and 78.76 percent (50 mm h^-1), respectively, and 45.01, 35.57, and 10.45 percent (of 90 mm h^-1), respectively. The effect of conservation treatments, soil moistures, and rainfall intensity and the interaction effects of conservation treatments × rainfall intensity and rainfall intensity × soil moisture on changes of soil loss and sediment concentration were significant at the level of 99 percent. The application of vermicompost and nano-manure had acceptable results on studied parameters but the vermicompost effect was more than nano-manure. Therefore, due to the widespread use of different types of conditioners, nowadays, it is needed to move the application feasibility of conditioners such as vermicompost and nano-manure that these have not the adverse effects of environmental.