| Summary: | 碩士 === 國立成功大學 === 水利及海洋工程學系碩博士班 === 97 === The vegetation on the floodplains of alluvial streams can increase the flow resistance. Flood dominant discharge may thus change its distribution over the bankfull stage and effect mainstream geomorphology evolution and construction safety. The purpose of this research was to investigate the discharge distribution in compound channels of high water stage.
Slope-area method theory was applied to develop the discharge distribution calculation model in vegetated compound channels based on the assumption that the friction energy slope of mainstream and floodplain equals with that of the full cross-section during high water stage. Flood discharge and mainstream discharge could then be estimated.
This research also conducted laboratory experiments of vegetated compound channel to test the friction energy slope hypothesis and the discharge distribution calculation method. Based on the experimental results , although the mainstream discharge and the full cross-section discharge were overestimated due to overestimated mainstream friction energy slope and underestimated floodplain friction energy slope by assuming equivalence of friction energy slope , the suitability is satisfactory. Ratio of the full cross-section discharge and the experimental discharge by the calculation is approximately 1.0∼1.5. The calculated ratio of the mainstream discharge and the full cross-section discharge shows approximately 1.0∼1.3rd times of that of gauging data.
This research also analyzed the influences of floodplain vegetation on the friction factor and the discharge. Because the stem clearance width influences flow condition , this circulation conductivity factor can be indicated as：
（3-2）
In the above equation , Bv is vegetated floodplain width , nb is the vegetated stem number of width Bv , d is the stem diameter. From the experimental results , the relationship of Fr and the friction factor fv can be shown as follows：
（4-10）
|
|---|
