| dc.description.abstract | In early times, river engineered construction in Taiwan concentrated only on the stability and flood control of a river, while ignoring the influences on environment and habitats of fish. This research discusses the influence on the living creature’s habitats area after the building of a spur dike.
Fazih River was chosen as the study area and the acrossocheilus paradoxus as the target fish species. HEC-RAS and River2D are combined to investigate the influenced area of spur dike, and 5% change of WUA (Weighted Usable Area) is set as the threshold to define the spur dike’s influenced area. Furthermore, the references of spur dike in the recent 10 years published in Taiwan are reviewed and analyzed with respect to variant factors for construction of spur dike, such as the width of channel, height or length of the dike, elevation, group of spur dikes and flow discharge.
The result shows that in spite of the length of the dike, the influenced area downstream is farther than the influenced area upstream. After building a spur dike, the farthest influenced area upstream can reach up to 2.5L, while the farthest influenced area downstream can reach up to 9L(L means the Dimensionless influenced area). Taking the Fazih River as a simulation, when the ratio of spur dike and width of channel (the length of spur dike / the width of channel ) is over 85%(discharge is 40 cm), spur dike is able to reach the water and take effect on the river. In the same channel, the ratio of influenced area (downstream/ upstream) will increase while the length and height of spur dike are increasing, but will decrease while elevation and discharge are increasing. When the discharge is approximate to 10 years return periods, the ratio of influenced area will be close to a constant value 2. Building double spur dikes for simulation will produce a better WUA than building single spur dike. When the ratio (Length of dike / Length of channel) is 1/10, single spur dike will produce a higher ratio of influenced area than the group of spur dikes. When the ratio (Length of dike / Length of channel) is 1/6, and the distances between the group of spur dikes are 1.5 times as the length of spur dike, we will get a higher ratio of influenced area. The result also shows that when the heights of the group of spur dikes are higher than the elevation of water surface, it will also produce a higher ratio of influenced area.
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