Dynamics of Sediment Hysteresis Patterns during Storm Events

Understanding and quantifying the dynamics of suspended sediment transport is essential to control soil erosion and implement appropriate mitigation practices to reduce stream suspended sediment and on-site and off-site effects of sediment transport. However, the quantification and the interpretation of sediment hysteresis loops as fluvial and hydrological responses of the watershed to storm events has been less considered. Hence, the present study was conducted in three different regions viz. the Educational and Research Forest Watershed of Tarbiat Modares University in Mazandaran, the Galazchai Watershed in West Azerbaijan and the Daretefi Watershed in Kurdistan Provinces to investigate the dynamic of sediment hysteresis loops on storm wise basis. The results of analyzing 67 storm event hysteresis loops verified the variety of governing condition of all three study watersheds. According to the results, all of the sediment hysteresis loops showed flushing behavior but with different rotational patterns of clockwise, counterclockwise and 8-typed and complex. Despite of differences and more diversity of precipitation pattern, compared with two other study watersheds, Daretefi Watershed sediment hysteresis loops showed less variety and mainly with 8-typed and complex forms with frequency of 61.29%. Results also revealed a frequency of 44% for both clockwise and complex hysteresis loops in the Galazchai Watershed and frequency of 53.33% for complex hysteresis loops in the Educational and Research Forest Watershed of Tarbiat Modares University. The results also showed that the sediment sources in the study watersheds were mainly close to the outlet with further emphasis on wash load contribution.