| Summary: | 博士 === 國立中興大學 === 水土保持學系所 === 101 === This study uses field survey to examine the wood debris characteristics and distribution in the Qijiawan Catchment. The stand wood volume in the bare area and wood debris volume used to build an association of wood debris budget. Using the unit stream power discusses the wood debris migrations. This study, then, addresses the concept of wood debris management.
The wood debris in the Qjijawan Catchment is a result of landslides. Total of 2,014 wood debris and the quantity are 1,384 m3 recorded in Qijiawan Creek, Gaoshan Creek, and Taoshan Creek during the February to July, 2008. The wood debris budget in the Qijiawan Catchment is 9.7%. This shows the wood debris in the study area is unstable and easy to transport downstream during flood events. The wood abundance and unit volume increased downstream, and wood density decreased downstream within a channel network. Moreover, channel morphology, riparian vegetation, and woody debris characteristics influenced wood storage in the study area.
The numbers of wood debris pieces entered and exited the study area due to the Typhoon Morakot were 128 and 61, respectively, from the January to September, 2009. There, then, were 554 and 107 wood debris pieces entered and exited the study area due to regular flood events from the September, 2009 to September, 2010. During the Typhoon Morakot, the stronger unit stream power (1,037 N/m/s) induced the wood debris increased 1,989 m3/ha. However, the man-made disturbance induced the wood debris decreased 570 m3/ha in the lower unit stream power (230 N/m/s) in 2010. In addition, the CCHE-2D model has an appropriate ability to demonstrate the relationship between the wood debris storage and the water level variation during the flood event. The wood debris storage can alter channel hydraulics; however, the wood debris dam development can create the variation of local channel properties, such as lifts the bed elevation and prevent the sediment transport.
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