Evaluation the relationship between rainfall erosivity index and sediment yield in Sanganeh area, Khorasan Razavi, Iran

Abstract

Rainfall erosivity, considering rainfall amount and intensity, is an important parameter for soil erosion risk assessment. The aim of this study was to evaluate the relationship between rainfall erosivity and sediment yield in Sanganeh area located in Naderi Kalat, Khorasan Razavi Province of northeastern Iran. The sediments load collected during the 17 rainfall events were measured in plots which had been prepared for this work from 2006-2009. For each rainfall, the duration of rainfall was divided into small uniform intervals and kinetic energy of each time interval was calculated. Then, the maximum intensities of rainfall events for 10 (I10), 15 (I15), 20 (I20), 25 (I25), 30 (I30), 35 (I35), 40 (I40), 45 (I45), 50 (I50), 55 (I55), and 60 (I60) minutes were calculated using hyetographs. The relationship between errosivity indices and measured sediment contents in all 17 plots was studied. The analysis of rainfall data revealed that maximum intensity of 45, 50, and 10 minutes (mm h-1) had the high correlation coefficient with sediment values. Because the frequency of rainfall events with high intensity in arid and semi-arid area is low, therefore, the maximum intensity of 10 minute (mm h-1) can be used for estimating the rainfall erosivity instead of 30 min hr-1 in USLE.