Evaluation of impact of spur dike designs on enhancement of aquatic habitats in urban streams using 2D habitat numerical simulations

Abstract

Although channelized urban streams provide aesthetic and economic value, they reduce biodiversity and alter the habitats of aquatic organisms. Spur dikes not only prevent the erosion of riverbanks, but also generally improve aquatic habitats. River 2D is widely used to analyze the aquatic habitats. However, the model often faces a challenge of lacking sediment and riverbed evolution module, which is difficult to predict the change of aquatic habitats. In this study, a depth-averaged habitat model, which couples a two-dimensional water-sediment shallow water model with an Instream Flow Incremental Methodology (IFIM), was provided to evaluate the impact of spur dikes on the improvement of aquatic habitats in the Jinjiang Stream in Chengdu, China. The potential value of aquatic habitats was quantitatively evaluated by a weighted useable area (WUA). Under different spur dike scenarios, the WUA is greater than under natural conditions, that is, the construction of spur dikes is beneficial for improving the habitat of aquatic organisms in urban rivers. In addition, further analysis from the simulation results shows that the three-spur dike scenario with a flow of 40 m³/s represents the best layout of spur dikes. Our study indicates that adjusting the spur dike layout is an effective instrument to enhance aquatic habitats, and can provide a certain reference for water ecological restoration and river management.