| Summary: | 博士 === 國立中興大學 === 水土保持學系所 === 99 === The surface soil in the watershed normally are eroded, transported and deposited by extrinsic force. This phenomenon can be explained from the apparent distinction between upstream soil erosion and sediment yield at the basin outlet. Nowadays, numerous soil erosion models and sediment transport equations have been developed for predicting the soil erosion and sediment yield in the watersheds, and the gap of them can be expressed by the Sediment Delivery Ratio (SDR).
Owing to the effective analysis of SDR, which explains the gap between the soil erosion and sediment yield in the watersheds, it can be practically applied to the discussion of watershed and sediment management. By the analysis of sediment delivery, SDR can effectively reflect the good and bad conditions of the watershed and the extrinsic affected factors; and therefore SDR becomes the basic index for the evaluation of watershed management. The study establishes a hillsides sediment delivery system according to the mathematic equation characteristics of SDR. The system discusses the SDR of the watershed and sediment units by different scales. By spatial distribution theory we analyze the affecting factor of sediment delivery and using physiographic and hydrologic characteristics explains the process of sediment delivery and further establishes a watershed sediment delivery model. Using the decomposing of delivery process and the adoption of sediment model we explore the characteristics of parameters of sediment delivery. The smaller the value of the sediment delivery parameters is, the higher the capability of the watershed sediment delivery carries, and so forth the greater the value of the reflective SDR.
The change of the amount of reservoir sedimentation is often the index of the effect of watershed management. This study aims to compare the difference of management and non-management sediment curves to specifically explain the effectiveness of sediment-decreased and capacity-increased and further apply the result of SDR combining with yearly amount of reservoir sedimentation, amount of sediment storage dam, and the amount funds invested in, etc. to make a time-variance analysis of Completeness Ratio (CR). The study shows that the bigger the areas of the watershed are, the smaller the value of the watershed CR; on the contrary, the higher the funds invested, the greater the value of the watershed CR is.
The study tries to find out the spatial distribution of SDR and the long-term changes of CR by investigating SDR and CR of the Shimen reservoir. After changing parameters of sediment delivery then we can evaluate the relatedness of CR between before- and after-management and make a CR goal to help follow-up management plan and for effect-evaluation reference.
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