Integrating river ecohydraulics in urban stormwater management

保护城市河流生态系统，同时提供通往河岸公园的通道，是加拿大许多市政当局提高市民生活质量的共同目标。城市河流和河岸是当地动植物的家园，为城市居民提供了绝佳的娱乐机会。人们很容易忘记，它们是城市排水系统的主要组成部分，因为它们在一种情况下疏散雨水，而在另一种情况下是实施雨水池的场所。虽然河岸上的植被在降低径流到达河流的速度方面起着重要作用，但雨水下水道网络是最大的加速器，与自然径流相比，它排放雨水的速度更快。这在暴雨期间通过相对高速的点排放对河流水力学产生直接影响，这往往会扰乱暴雨出口附近以及下游的河流生态系统。此外，雨水还从城市景观的径流中携带潜在的污染物，这可能对当地生态系统产生负面影响。在降雨强度谱的较低范围内，城市河流的流量状况与自然河流的流量状况差异最大。这个范围也提供了最好的可能性，以恢复足够的水质和控制速度，然后释放到接收水域。由于魁北克东部夏季平均每三天降雨一次，为了保护城市河流流域的生态系统，综合雨水管理系统必须旨在提供适当范围的生态水力特征（流速和污染物负荷），以维持当地栖息地的生物多样性，以应对频繁的降雨事件。随着城市对河流的压力越来越大，传统解决方案的空间越来越小，成本增加，优化成为必要。通过增加雨水排放的实时控制（RTC）来优化现有的雨水系统是本项目所追求的解决方案。最重要的是，RTC提供了一种灵活调整系统（寿命为50-100年）以适应气候变化预期的降雨强度谱变化的手段。

Preserving urban river ecosystems while providing access to riverbank parks is a goal shared by many Canadian municipalities for improving the quality of life of their citizens. Home to local fauna and flora, urban rivers and their riverbanks offer great recreational opportunities for city dwellers. It is easy to forget that they constitute a major part of the municipal drainage system, as they evacuate stormwater in one case, and are sites to implement stormwater ponds in the other. While vegetation on riverbanks plays an important role in decreasing velocities at which runoff reaches the river, the storm sewer network is the greatest accelerator, discharging stormwater more rapidly compared to natural runoff. This has a direct impact on river hydraulics through point discharges at relatively high velocities during rainstorms, which tend to disturb river ecosystems in the vicinity, as well as downstream, of the storm outlets. Furthermore, stormwater also carries potential contaminants from runoff on the urban landscape that can negatively impact the local ecosystems. The flow regime of urban rivers differs most from the regime in natural rivers in the lower range of the rainfall intensity spectrum. This is also the range that offers the best possibilities for restoring adequate water quality and controlling velocities before release into the receiving waters. With rainfall events in Eastern Quebec on average every three days in summertime, an integrated stormwater management system for preserving ecosystems along an urban river reach must aim at providing the proper range of eco-hydraulic characteristics (velocities and pollutant loads) to sustain the biodiversity in local habitats for frequent rainfall events. As urban pressure on streams goes stronger, there is less space for traditional solutions, costs increase, and optimization becomes a necessity.Optimization of existing stormwater systems by adding real-time control (RTC) of the stormwater discharge is the solution pursued in this project. RTC provides, on top, a means to flexibly adapt the system (with a lifetime of 50-100 years) to the changes in rainfall intensity spectrum expected from climate change.