Assessing and restoring the resilience of urban stream networks

提出这项研究的动机是城市河流网络管理中的战略合作伙伴在决策过程中面临的不确定性。基本问题是，城市化增加了地表径流量和洪灾期间的洪峰流量。这些水必须通过在更为温和的水流条件下形成的河流网络进行输送。大范围的物质退化和生态系统服务的丧失，如清洁的空气和水、美学以及娱乐和教育机会，导致了所谓的“城市河流综合症”。雨水管理和溪流恢复是解决这一问题的两种可用但有限的技术，但它们往往不能如预期那样发挥作用，尽管成本高昂，气候变化构成了重大的额外威胁。 我们旨在解决的研究差距是不同管理情景下城市小溪河床泥沙对洪水的响应。实地研究将集中在大多伦多地区的三个地点，即未进行雨水管理的Wilket Creek，采用管道末端雨水管理的Morningside Creek，以及计划在未来几十年开发的Ganetsekaigon Creek。Ganetsekaigon Creek目前是红尾鱼健康种群的家园，这种鱼在安大略省被列为濒危物种。量化沉积响应对于了解这些系统中的生态系统弹性至关重要，因为构成河床的沉积物是藻类和底栖无脊椎动物的物理栖息地，而藻类和底栖无脊椎动物是水生和河岸生态系统食物网的基础。在城市河流管理的实践中，关于泥沙供应和通过河道的路线选择的问题几乎没有受到重视，我们将尝试通过创新的实地工作、泥沙动力学的实验室研究以及通过与我们的合作伙伴进行嵌入研究来开发决策支持工具来解决这个问题。我们还将评估一种基于泥沙供应管理的新方法，该方法有可能重新平衡实物河流网络并恢复生态系统服务。

The proposed research is motivated by the uncertainty in decision making processes faced by strategic partners in the management of urban stream networks. The basic problem is that urbanization increases the volume of surface runoff and the magnitude of peak discharges during floods. This water must be routed through stream networks that developed under much more moderate flow regimes. Widespread physical degradation and loss of ecosystem services such as clean air and water, aesthetics, and recreational and educational opportunities lead to what is called the "urban stream syndrome". Stormwater management and stream restoration are two available but limited techniques for the issue, but they often do not work as intended despite significant costs, and climate change poses a significant additional threat. The research gap we aim to address is the response of channel bed sediment to floods in urban creeks under different management scenarios. The field research will focus on three sites in the Greater Toronto Area, namely Wilket Creek, developed without stormwater management, Morningside Creek, developed with end-of-pipe stormwater management, and Ganetsekaigon Creek, slated for development in the coming decades. Ganetsekaigon Creek is currently home to a healthy population of Redside Dace, which is listed as an endangered species in Ontario. Quantifying the sedimentary response is critical for understanding ecosystem resilience in these systems because the sediments comprising the river bed are the physical habitat of the algae and benthic invertebrates that underpin the food web in aquatic and riparian ecosystems. The issues surrounding sediment supply and routing through a channel have received little attention in the practice of urban stream management and we will attempt to address this problem with innovative field work, laboratory studies on sediment dynamics, and the development of a decision making support tool through embedded research with our partners. We will also assess a new approach based on sediment supply management that has the potential to rebalance the physical stream network and restore ecosystem services.