Ali Golkarian
Abstract
Erosion is one of the important factors in soil degradation and decrease fertility and slope length is one of the most effective factors in land form and amount of erosion. The objective of this study was investigation of spatially variation of sediment concentration in slope length until to receive ...
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Erosion is one of the important factors in soil degradation and decrease fertility and slope length is one of the most effective factors in land form and amount of erosion. The objective of this study was investigation of spatially variation of sediment concentration in slope length until to receive transport capacity. To obtain this goal a hill slope simulator system designed and manufactured. This system include 10 flumes, each has five meter length which after series them become fifty meters. This system can produce cumulative flow via fifty watering can tube which are install on flumes with one meter interval and each flume discharging is 100 cc. Other variables include two type of soil and slope in three level 15, 22.5, 30 percent. Three replications were used for each treatment and totally 18 experiment was done. In each experiment four samples were gathered from end of each flume and concentration was determined. Complete randomized design with factorial arrangement was used for data analyzing. Richard’s function was used for fitting a suitable curve on observed data. Result was shown that effect of soil type on sediment concentration was not significant while slope and slope length effects was significant. Otherwise sediment concentration in the two last flumes was located in same class which is shown that sediment concentration achieved to transport capacity in this slope length. Also results were shown that Richard’s function can simulate trend of concentration variety in slope length.
ali shahbazi; Shahram khaliqi sygarodi; Arash Malekian; Ali Salajegheh
Abstract
In order to decrease the risks associated with the management of urban watersheds, the use of proper methods is an essential task to estimate the runoff with a high degree of confidence. Time of concentration is one of factors that impacts on peak discharge and runoff volume. The objective of this study ...
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In order to decrease the risks associated with the management of urban watersheds, the use of proper methods is an essential task to estimate the runoff with a high degree of confidence. Time of concentration is one of factors that impacts on peak discharge and runoff volume. The objective of this study is to select the best method among the empirical formulas for estimating the time of concentration. In this study, for determination of actual time of concentration, the field method based on measuring the travel time by using floating-object method was employed. To select the best empirical formula of the time of concentration, the statistical criteria including percentage Relative Error (RE), Root Mean square error (RMSE), Average percentage Relative Error (RME), Nash - Sutcliffe criteria (NS) and determination coefficient were used. Then, differences among the estimations obtained from empirical equations were compared with the actual values. The results of this study based on comparison of the relative error in each interval showed that in the reach No. 2, empirical formulas of California, Chow, Carter and Federal Aviation, with percentage error of 2.7, 2.9, 4.4 and 4.4 have showed the best estimation, respectively. The equation proposed by Kirby with percentage error of 1 in the reach No. 3, the equation of Ventura with percentage error 8.5 in the reach No. 9 and the equation of rational hydrograph with percentage error 4.8 in the reach No. 10 have showed the best estimates. Therefore, it is recommended to use the empirical formula that has the lowest percentage of error for areas with features similar to the studied reaches. In general, the results show that only rational hydrograph method in all of the reaches has the lowest error and then provides the most proper estimates compared than others.
Salman Zare; ali Tavili; ali Shahbazi; akbar Riyahi
Volume 63, Issue 1 , June 2010, , Pages 29-40
Abstract
The objective of this research was to evaluate the effect of different concentration of salicylic acid on enhancement germination characteristics of Sanguisorba minor L. under salt and drought stress. The experimental design was factorial arranged in a completely randomized block design with four replications. ...
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The objective of this research was to evaluate the effect of different concentration of salicylic acid on enhancement germination characteristics of Sanguisorba minor L. under salt and drought stress. The experimental design was factorial arranged in a completely randomized block design with four replications. Treatment were combination of 5 levels of salt and drought stress, separately (0, -0.3, -0.6, -0.9 and -1.2 Mpa) and 4 concentration of salicylic acid (0 as a control, 100, 200 and 300 mg/lit). The results revealed that all germination characteristics decreased by increasing strength of salt and drought stress but treated seeds showed lower decrease. Application of salicylic acid increased germination percentage and rate and also decreased mean germination time significantly, but had no effect on root, shoot and seedling length. Since 200 and 300 mg/lit concentrations of Salicylic acid had more effect than the 100 mg/lit on germination attributes, on the other hand no significant difference was observed between 200 and 300 mg/lit concentrations. Considering the economic issues and also considering this fact that higher concentrations of salicylic acid may lead to accelerated stress in plant, 200 mg/lit salicylic acid concentration was suggested in S. minor in order to improve germination and seedling establishment under salt and drought stress.