| dc.description.abstract | Avoiding floods and building dikes is the main river protection policy in the early period of Taiwan. However, nowadays environment protection becomes an important issue and the Ecological Engineering Method was taken into account for the protection of river. When renovating rivers, people not only have to consider the safety and wealth of humans but also the protection of environment and ecology. Before when people renovating rivers, engineers do not consider the living creatures in rivers and their needs, it’s possible to affect the balance of ecological system and also reduce the variety of habitats. According to these reasons below, this research report is probing the positive and negative effects of the hydraulic structures to the living creatures in river.
The research chose Fazih River as the study area and the acrossocheilus paradoxus as the target fish. HEC-RAS and River2D were combined to produce a simulation and to design Groundsill、Spur dike into three different sizes : short Spur dike(20m)、 medium Spur dike(30m)、long Spur dike(40m)、Groundsill(1m)、Groundsill(1.25m) and Groundsill(1.5m). The Weighted Usable Area (WUA) by making a simulation of the twenty four samples were estimated.
When the flow Q=4.6cms~130cms is added, the WUA of Spur dike is very close to the original; when the flow Q=160cms~590cms, the WUA of Spur dike is lower than the WUA of original river. When the flow Q=4.6cms~220cms, the WUA of Groundsill is higher than the WUA of original river; when the flow Q=238cms~590cms, the WUA of Groundsill and the WUA of original river differences are not big. The result shows that when the flow is in the low part, the influence of the Groundsill is positive. And in the high flow section, no matter if it’s short, medium or long Spur dike, the WUA is lower than the original or groundsill one.
The determined standards are 5%, 3% and 1.5%. As for the spur dike, the smaller the determination standard, the bigger the influenced area; and the longer the spur dike’’s length, the further the influenced area. As for groundsill, the three criteria have shown that the influences area in upstream has exceeded the studying area by 60 meters; the influenced area in downstream expands along with the reduction of critiria.
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