Stormwater Management and Watercourse Impacts: The Need for a Water Balance Approach




A Report to the Toronto Region Conservation Authority

Published in November 2006 by the Toronto Region Conservation Authority, the report titled Storm Water Management: The Need for a Water Balance Approach examined the premises behind current management strategies and concluded that there is a clear need for a paradigm shift in rainwater/stormwater management practice:

  • While end-of-pipe solutions have been effective to a degree in reducing flood flow and water quality impacts, current science points to the need for a water balance approach that promotes additional source and conveyance controls to minimize the increase in runoff generation from urban landscapes and reduce impacts to receiving watercourses and the aquatic habitats that they support.”


Results of Literature Search

The report describes how changes in land use from a natural vegetated condition to agriculture and urban development have altered, and continue to alter, the sediment and hydrologic regime of receiving watercourses: “Such changes result in adjustments at the micro, meso and macro scale of channel form, which have implications for exacerbated erosion, increased risk to safety, property and infrastructure, and degradation of aquatic habitat.”

Through review of the literature, the report states that it is apparent that the hydrologic impacts of urbanization have been studied globally, spanning several continents:

  • “Recognition of adverse effects has led to a progression of evolving stormwater management strategies, each of which has  attempted to minimize impact of urban runoff on the flow regime of receiving watercourses.”
  • “While these efforts have resulted in reduction of some impact, research has shown that the current state of practice with respect to stormwater management is not sufficient to mitigate the impacts of land use change and urban development on channel stability and aquatic habitat.”

The report emphasizes that progressive jurisdictions are developing water balance approaches to rainwater/stormwater management for urban development to mitigate the geomorphic and biotic impacts that result from current practice. Such approaches utilize best management practices to infiltrate or evaporate water and minimize increases in runoff volume.

To download a copy of the report, click on this link: Storm Water Management: The Need for a Water Balance Approach. To access related information and resources on the Sustainable Technologies website, please click here.


Posted July 2008