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，是许多加拿大市政当局改善其公民生活质量的共同目标。作为当地动植物的家园，城市河流及其河岸为城市居民提供了巨大的娱乐机会。人们很容易忘记，它们构成了市政排水系统的主要部分，因为它们一次是疏散雨水，另一次是实施雨水池。虽然河岸上的植被在降低径流进入河流的速度方面发挥了重要作用，但雨水管网是最大的加速器，与自然径流相比，它排放雨水更快。这对河流水力有直接影响，因为在暴雨期间，点以较高的速度排放，这往往会扰乱风口附近和下游的河流生态系统。此外，雨水还携带来自城市景观径流的潜在污染物，可能会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，城市河流的流态与天然河流的流态差异最大。这也是在释放到接收水域之前，为恢复足够的水质和控制流速提供最佳可能性的范围。由于魁北克东部夏季平均每三天发生一次降雨事件，一个用于保护城市河段生态系统的综合雨水管理系统必须旨在提供适当范围的生态水力特性(流速和污染物负荷)，以维持当地生境中的生物多样性，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。

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.