| Summary: | 碩士 === 國立屏東科技大學 === 水土保持系 === 90 === Non-agricultural development on sloping lands has become one of the trigging factors that cause sediment disaster. Even though they are listed and required in the current “Soil and Water Conser-vation Regulation”, temporary disaster prevention measures often create side issues like less economic land use, capital increase, and defective installation. Therefore, the objective of this study is to in-vestigate the sediment trapping efficiency of silt fences.
Through indoor simulated erosion studies and outdoor plot studies, a series of silt fence interval estimation equations has de-veloped for the coarse- and fine-opening silt fence at different slope gradients and installation intervals. Users can use these equations to estimate the silt fence installation interval based upon the slope gradients, desired sediment trapping efficiency, and possible land use restrictions.
Silt fences do not provide sufficient detention efficiency for surface runoff. The runoff detention efficiency is within 30 — 70%, and it can be less than 20% as slope gradient increases. Neverthe-less, the installation of silt fence can greatly reduce runoff velocity and sediment transport capacity. On the other hand, the pseudo-plunging flow caused by surface runoff while it overflows the silt fence can initiate the scour at the toe of the fence. From the economic point of view, silt fence not only effectively controls on-site sediment, but also reduces the cost yet maintain economic land use. If the concentration of suspended solid in the surface run-off escaping from silt fences can meets the local requirements, choosing silt fences as temporary disaster countermeasure can be one of the operational options.
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