Author(s): Sameh Kantoush; Mahmood M. Al-mamari; Tahani Al-harrasi; Mohamed Saber; Tetsuya Sumi

Linked Author(s): SAMEH KANTOUSH, Mohamed Saber, Tetsuya Sumi

Keywords: Reservoir sedimentation, Sediment yield, Wadi sedimentation,

Abstract: The kinetic energy of infrequent extreme rainfall events like cyclones erodes soil in the wadi watershed in Oman. Local erosion and sediment transport processes along the wadi channel occur according to the generated rainfall runoff. Estimating sediment yield, erosion and deposition processes, and reservoir sedimentation are vital for the efficient water resources management of dry environments with limited observation data and scientific understanding. However, few empirical approach models were modified and investigated to predict sediment yield in the ephemeral stream. Generally, the characteristics of flash floods and rainfall patterns in arid regions differed from the perennial stream. The sharpness of peak discharge and spatial and temporal rainfall distribution with high intensity causing aggravate soil erosion with a significant impact on the life span of many hydraulic structures. While flash floods in these regions are essential sources for groundwater recharge and water supply, several dams were constructed in the wadi channel (ephemeral stream) for water harvesting and flood control. However, the primary concern of the dam reservoir was siltation, which caused fast losses of original storage capacity and high degradation for a downstream channel. Therefore, monitoring and managing sediment transport is very important in evaluating management options both for the sustainability of water resources and dam reservoir management. The main objective of this study is to estimate the sediment yield and reservoir sedimentation in the arid wadi system. The study focuses on assessing sedimentation and upstream morphological changes in the wadi channels by combining different methods. Finally, studying the relationship between the sediment erosion and transport volumes and the extreme flash flood events parameters such as rainfall intensities, events duration, and number of rainy days This study determined the sediment yield from a dam reservoir by conducting four field surveys for the Asserin dam in Oman (November 2017, September 2018, March 2019, and August 2019) to collect sediment levels from 19 sediment scale bars. Those data were computed using GIS to quantify the sediment volume in the reservoir. The correlation between trapping sediments and the accumulated rainfall depth was developed with a high coefficient (R2=0.87). On the other hand, the flow rate was modeled for a series of rainfall events that contributed to reservoir sedimentation using the Rainfall-Runoff-Inundations (RRI) model. The discharge result shows reasonable agreements with deposited sediments in the dam reservoir. Finally, this research will review and compare different models generated and investigated to predict sediment yield in wadi catchments from an independent literature review.

DOI: https://doi.org/10.3850/IAHR-39WC252171192022SS1288

Year: 2022