| Summary: | 碩士 === 國立臺灣海洋大學 === 河海工程學系 === 105 === Check dam is an important structure for sediment control in upstream watershed. The major functions of the check dam are sediment yield reduction and channel bed stabilization. Accuracy of the prediction of sediment deposit slope is the key factor for the estimation of sediment deposition volume and the design space between check dams. In this study, 17 check dams, located in Keelung, Hualien, Taitung, and Nantou, were investigated following the coordinate data provided by the Soil and Water Conservation Bureau. The deposition slopes behind the check dam, the width and height of the check dam, the size of deposited sediment particles were measured. The distribution of bed material grain sizes was obtained by the image processing and identification technology using a digital sieving software based on the surface-sediment particle photos taken from the field investigations. The digital sieving method can alleviate the requirement of labor intensive and time consuming problems in using traditional sediment sieving method.
In this study, digital elevation model was used to calculate the watershed area and to extract the original channel slope before the construction of the check dam. The design discharges under different return periods were estimated by using the rational method. Multiple regression method was applied to analyze relationship between the deposition slope and the geomorphologic and hydrological factors of the check dam watershed. The results show that the original slope is the most important influence variable. If the original channel bed slope is the only variable for the regression analysis, the coefficient of determination is about 0.848. For variable including original channel bed slope, sediment particle size, and discharge, the coefficient of determination can reach to 0.875 for the regression equations.
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