Assessment of Corrective Methods for Estimating Suspended Sediment Load for Rivers with Debris Sediment Flow Regime in Khorramarood River - Golestan Province

    In the present research, changes in sediment regime in two statistical periods of "natural flow" and "modified / debris flow" were evaluated. In order to determine the significant difference between two mentioned periods (1966-1992) and (1993-2015), the significance test was used. In order to determine the most suitable method of Sediment Rating Curve and correction coefficients, the results of simple linear, bilinear, midline rating curve methods as well as the mentioned rating curves with correction coefficients including correction coefficients of FAO, MVUE, QMLE and Smearing methods were evaluated. The results showed that since 1993, with the onset of large floods, the sediment discharge regime with a high intensity and increasing trend is out of normal and in the period 2011 to 2015, the highest rate of sediment transfer in the form of debris flow has occurred. Among the methods, the one-line curve method and the smearing correction factor for the natural sediment regime period (1966-1992) and the two-line curve method and the smearing correction coefficient for the modified sediment regime / debris flow period (1993-2015) are more accurate in estimating sediment flow. On the other hand, the one-line curve method without taking into account the correction coefficients have a higher low estimation error and among the mentioned correction coefficients, the FAO coefficient has a very high overestimation error. In the batch middle method, sediment estimation at high discharges is improved by reducing the effect of low points.