| Summary: | 碩士 === 華梵大學 === 環境與防災設計學系碩士班 === 97 === The Nan-Shi-Keng mountainous stream, a stream near Huafan University, located in Shidin township, Taipei county is selected to study the influence of remediation work on the stream in this study. The data, including the Digital Terrain Model（DTM）, flow depth, flow velocity, substrate and fish distribution, etc., in the mountainous stream were collected. Two hydraulic simulation models, one-dimensional HEC-RAS model and two-dimensional FLO-2D model, were applied to evaluate the flow depth and flow velocity at various flowrates. Three fish habitat suitable curves, including the flow velocity, flow depth and substrate, in the study area are used. Then the Habitat Suitability Index（HSI）and Weighted Usable Area（WUA）can be determined by multiply and geometric methods, respectively, based on the fish habitat suitable curves.
Simulation results of hydraulic models show that the average flow depth increases and no significant indication for the average flow velocity changes after the stream remediation. Values for HSI or WUA obtained by the multiply and the geometric methods are different but both methods indicate that they have similar tendency for the relation of the HSI or the WUA and the flowrate. The average HSI value, , for the stream after remediation is slightly smaller than that before remediation when the flowrate is greater than 3 cms. When the flowrate is less than 3 cms, no significant difference was shown before and after remediation for the value. The value of WUA for the stream before remediation is greater than that after remediation. The WUA value was decreased by 20%~40% after stream remediation when the flowrates are in the range of 3 to 15 cms. The influence on the habitat areas for various habitat types shows that the areas for pool, riffle, and run after stream remediation were decreased by an average around 40% after stream remediation.
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