梯形透空丁坝局部水动力特性对底栖动物生境演替的影响机制

针对因梯形透空丁坝局部水动力特性对底栖动物栖息地的影响机制尚不明确，限制了此类结构的大范围推广应用的问题，依托长江深水航道建设的示范应用工程，构建三维水动力数值模型，选择中华绒螯蟹为指示物种，研究了不同径流条件下梯形透空丁坝局部水动力特性及其对指示物种栖息地的影响；结合梯形透空丁坝不同时期沉积物和底栖动物的监测数据，分析了梯形透空丁坝对底栖动物生境演替的影响机制。结果表明：梯形透空丁坝迎流面产生的上升流将主流引导至丁坝后上方，在汛期为中华绒螯蟹提供了避洪场所；坝内及坝后较小的流速和丰富的流场结构为中华绒螯蟹提供了索饵场和越冬场。

Influence mechanism of local hydrodynamic characteristics of trapezoidal hollow spur dike on benthos habitat succession

The impact mechanism of trapezoidal hollow spur dike on benthos habitat due to local hydrodynamic characteristics is still unclear, which limits the large-scale promotion and application of such structures. Relying on the demonstration application project of the Yangtze River deep-water channel construction, a three-dimensional hydrodynamic numerical model was established, and the Chinese mitten crab was selected as the indicator species to study the local three-dimensional hydrodynamic characteristics of trapezoidal hollow spur dike under different runoff conditions and their impact on the habitat of the indicator species. Combined with the data analysis of sediment and benthos monitoring in different periods of trapezoidal hollow spur dike, the impact mechanism of trapezoidal hollow spur dike on benthos habitat succession was revealed. The results show that the upwelling generated on the upstream face of the trapezoidal hollow spur dike leads the mainstream to the upper part behind the dike, providing a flood shelter for Chinese mitten crab in the flood season. The small flow velocity and abundant flow field structure in and behind the dike provide feeding grounds and overwintering grounds for Chinese mitten crabs.