丁坝对鱼类栖地的影响范围评估

Estimation of spur dike-affected fish habitat area

基于一维水理模式(HEC-RAS)和河川栖地二维模式(River 2D),以5%权重栖地可使用面积(weighted usable area,WUA)增减率判定筏子溪丁坝对台湾石鱼宾的影响范围,并结合近年台湾地区丁坝设置的相关文献,探讨丁坝对鱼群栖地的影响范围以及丁坝建置要素[如坝高、坝长(阻水率)、流量、河道平均坡降、单双丁坝]对其范围的影响.结果表明:丁坝对下游的影响范围皆远于上游,下游影响范围约为上游的2～6倍.上下游影响范围之比随坡降增加而下降、随丁坝阻水率及流量增加而增加,但流量趋近至10年重现期距时,上下游影响范围比趋于2.双丁坝配置较单丁坝配置有较优的WUA.

Based on the HEC-RAS and River 2D modes,and taking 5% change rate of weighted usable area（WUA） as the threshold to define the spur dike-affected area of target fish species Acrossocheilus paradoxus in Fazi River in Taiwan,this paper studied the affected area of the fish habitat by spur dike,and,in combining with the references about the installations of spur dikes in Taiwan in recent 10 years,analyzed the relative importance of related affecting factors such as dike height,dike length（water block rate）,average slope gradient of river way,single or double spur dike,and flow discharge.In spite of the length of the dike,the affected area in downstream was farther,and was about 2-6 times as large as that in upstream.The ratio of the affected area in downstream /upstream decreased with increasing slope gradient,but increased with increasing dike length and flow discharge.When the discharge was approximate to 10 years return periods,the ratio of the affected area would be close to a constant of 2.Building double spur dike would produce a better WUA than building single spur dike.