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Showing 2 results for Simulated Rainfall
Investigation of Soil loss from Small Plots with Different Soil Textures in Sequential Simulated Rainfall Events
A. R. Vaezi, H. Hasanzadeh,
Volume 20, Issue 75 (5-2016)
Abstract

Knowledge of variation in soil properties from each event to another is very important for the determination of critical periods during which soil is susceptible to erosion processes. This study was carried out to investigate soil loss in sequential rainfall events in Zanjan Province. Toward this, ten soil textures samples were taken and were transported to small plots (60 cm×80cm) with 20-cm depth) on a 8% slope land at three replications. The plots were exposed to ten simulated rainfalls with an intensity of 55 mm h-1 for 30-min and 5-day intervals. A total of 300 simulated rainfall trials were carried out at the plots.  Results indicated that soil moisture, runoff production and soil loss were significantly affected by rainfall events (P< 0.001). Increasing soil moisture and consequently decreasing soil infiltration capacity were the most crucial element in increasing runoff production and soil loss in the sequential rainfall events, in a way that about 84% of soil loss variation in the rainfall events could be explained based on antecedent soil moisture. After the fifths rainfall event, no significant differences  was found in soil infiltration capacity as well as runoff production because of soil moisture reaching to the water-holding capacity. Nevertheless, an increasing trend was observed in soil loss after fifth event which could associate with presence of more erodible soil particles on the surface and consequently increasing the concentration of surface flows.


Investigation of the Surface and Tunnel Runoff and Sediment Production in Saline-Sodic Soil under Different Slopes
S. Esmailian, M. Pajouhesh, N. Gharahi, Kh. Abdollahi,
Volume 27, Issue 3 (12-2023)
Abstract
Awareness of the number of changes in runoff and sediment on different slopes can be useful in modeling the production of runoff and sediment. Therefore, this study was conducted to investigate the production of surface and tunnel runoff and sediment in saline and sodic soils on different slopes. Saline-sodic soil was collected and transported to the laboratory. Laboratory experiments were performed on a soil bed in a rectangular flume at three different slopes (5%, 10%, and 15%) under simulated rain (30 mm/h) for one hour. An analysis of variance was used to investigate the effect of slope on runoff and sediment production, and the means were compared using Duncan's test at the five percent level using SPSS version 26 software. The results showed that there was a significant difference between the slopes of the runoff (P<0.001) and sediment (P<0.001). In the first minute of the experiments, due to the lack of moisture in the soil, the amount of runoff was low, but over time, the amount of runoff increased. It is because the pores are blocked by the dispersion of soil particles owing to the presence of sodium ions, which ultimately leads to a decrease in permeability. Similarly, in the last few minutes, outflow from the tunnel was observed, and this flow occurred only on slopes of 10% and 15%. The amount of sediment was also low in the first few minutes, which could be related to the low amount of runoff and the lack of sediment particle removal. Nonetheless, after the lapse of time, its amount increased, and the primary reasons were reduced permeability, increased runoff, and removal of fine particles from the soil surface.

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