Sediment trapping and hydraulic characteristics affected by different grass strip configurations

• Main Authors: Chi-Han Chiang, 蔣季翰
• Other Authors: Dr.C.-C. Wu
• Format: Others
• Language: zh-TW
• Published: 2009
• Online Access: http://ndltd.ncl.edu.tw/handle/76858473193209810404

碩士 === 國立屏東科技大學 === 水土保持系所 === 97 === Steep topography and rapid development has made all activities associated with human one of the key components contaminating watershed environment as well as degrading water quality. Researches have demonstrated that vegetative buffer strip is one of the countermeasures that capable of controlling the movement of pollutant. Vegetative buffer strip is also capable of creating and maintaining wildlife habitats. Nevertheless, lack of research support, implementation guidelines of vegetative buffer strip are needed for Taiwan; especially on steep topography and limited land areas. Hence grass strip experiments were conducted in a hydraulic flume. Experiment parameters included strip width, slope steepness, grass species, sediment size, inflow rate, and two configurations of hedge grass. And the objective of this study was to investigate how different grass configurations affecting sediment trapping efficiency and hydraulic characteristics within a grass strip. Following conclusion can be drawn from this study: Sediment trapping efficiency is found to be greatly affected by grass configurations. It is also affected by the strip width. As strip width increases, sediment trapping efficiency increases accordingly within the limits of experiment conditions. Experiment observations as well as flow velocity measurements also notice the continuous changes of surface roughness that alter not only the sediment runout time but also sediment discharge. Flume experiments were not in favor of implementing hedge rows on steep slopes; simply because hedge rows promote flow concentration that in turn help initiate rills and shorten sediment runout time. Increases in flow rate and slope steepness obviously decreases sediment trapping efficiency. At 9 % slope, the hedge rows provide additional sediment storage space; however, runoff concentration and rill erosion diminishes the storage space and decreases sediment trapping efficiency when slope steepness increases to 15 and 20%.