Abstract
The sediment delivery ratio (SDR) connects the weight of sediments eroded and transported from slopes of a watershed to the weight that eventually enters streams and rivers ending at the watershed outlet. For watershed management agencies, the estimation of annual sediment yield (SY) and the sediment delivery has been a top priority due to the influence that sedimentation has on the holding capacity of reservoirs and the annual economic cost of sediment-related disasters. This study establishes the SEdiment Delivery Distributed (SEDD) model for the Shihmen Reservoir watershed using watershed-wide SDRw and determines the geospatial distribution of individual SDRi and SY in its sub-watersheds. Furthermore, this research considers the statistical and geospatial distribution of SDRi across the two discretizations of sub-watersheds in the study area. It shows the probability density function (PDF) of the SDRi. The watershed-specific coefficient (β) of SDRi is 0.00515 for the Shihmen Reservoir watershed using the recursive method. The SY mean of the entire watershed was determined to be 42.08 t/ha/year. Moreover, maps of the mean SY by 25 and 93 sub-watersheds were proposed for watershed prioritization for future research and remedial works. The outcomes of this study can ameliorate future watershed remediation planning and sediment control by the implementation of geospatial SDRw/SDRi and the inclusion of the sub-watershed prioritization in decision-making. Finally, it is essential to note that the sediment yield modeling can be improved by increased on-site validation and the use of aerial photogrammetry to deliver more updated data to better understand the field situations.
Highlights
Land degradation has been confirmed as a threat to agricultural productivity worldwide [1]
Past studies have shown the distribution of soil erosion of the Shihmen Reservoir watershed, and this paper estimates the geospatially distributed sediment delivery ratio (SDRi) under a beta determined by the recursive method of the SEdiment Delivery Distributed (SEDD) model and a known watershed-wide SDR and the entire watershed (SDRw)
The SDR plays an essential role in soil erosion research as an additional parameter when considering sediment yield, slope conservation/remediation, and sediment control projects for engineers and decision-makers
Summary
Land degradation has been confirmed as a threat to agricultural productivity worldwide [1]. Taiwan’s geographical location places it in a precarious position that geomorphologically has a high frequency of highly erodible soil materials and, its tropical monsoon climate brings frequent extreme rainfall or typhoon events which have led to massive sediment loads, dissociated by mass movements, and soil erosion, to be transported from slopes of watersheds into rivers and streams, affecting water supply in many communities These events increase the siltation of reservoirs, such as the Shihmen Reservoir in Northern Taiwan, which diminishes the country’s capacity to sustainably manage its water supply and poses a threat to the long-term sustainability of the dam and the populations it serves [4,5].
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