Primer on Rainwater Management in an Urban Watershed Context


Note to Reader:

ISMP is the acronym for Integrated Stormwater Management Plan. In the late 1990s, the genesis for ISMPs was a desire by local governments to integrate the community, engineering, planning and environmental perspectives.

To fill a professional development need, the Partnership for Water Sustainability in British Columbia has developed a 2-day course titled ISMP Course Correction: Achieve More with Less. The City of Surrey hosted the first course on November 9-10, 2011.

As part of the course curriculum, the Partnership unveiled two Primers. These provide the technical foundation for the course curriculum. One primer deals with science-based hydrology, and the other with watershed modeling. The story below introduces the first.

ISMP Course Correction: Focus on Stream Health and Watershed Outcomes

BC is primarily a mountainous region. Headwater tributary streams are a predominant feature; and watershed health is very much about protection of aquatic habitat. The critical issue is the damage to and loss of habitat caused by land use change and resulting erosion of the headwater streams. BC’s habitat focus contrasts with the water quality emphasis in the United States and elsewhere in Canada.

The goal of protecting stream health has become a driver for action in BC. By 2002, as an implementation action resulting from enactment of the Fish Protection Act (1997), the Province released Stormwater Planning: A Guidebook for British Columbia. The Guidebook was a joint effort of two Ministries – Environment and Municipal Affairs. The process produced a science-based framework to guide development of the stormwater component of Liquid Waste Management Plans.

Science-Based Understanding

The purpose of the Primer on Rainwater Management in an Urban Watershed Context is to provide engineers and non-engineers with a common understanding of how a science-based approach to rainwater management has evolved since the mid-1990s:

  • First, research by Richard Horner and Chris May in Washington State identified limiting factors for stream health, and established an order-of-priority. Their findings provided a road map for integrated rainwater management.
  • Next, the “made in BC” concept of the Rainfall Spectrum led us to look at rainfall differently. This resulted in the Water Balance Methodology and the ability to quantify and assess the hydrologic effectiveness of ‘green’ infrastructure.
  • After that, a fresh look at other early engineering and biophysical research opened a window into the science of stream erosion and how it could be correlated with stream health.
  • The synthesis of the three streams of thinking then provided the technical foundation for ‘designing with nature’ in order to soften the ‘water footprint’ of development. In BC, we have continued to build on this foundation.

Pioneer research yielded guiding principles; these are standing the test of time. Evaluation of, and analyses using, the entire rainfall and stream discharge spectrum allows us to see new connections to stream health and to begin the process of creating effective mitigation strategies.

Updates to our scientific knowledge allow us to establish and implement more effective stream health protection as part of an ongoing adaptive management (i.e. ‘learn by doing’) process.

Understand How a Watershed Functions

“Watersheds are not all created equal. And when we begin to examine them, we find that they function in all kinds of different ways. And what I often see missing in most engineering methodologies is an understanding of how a particular watershed actually functions,” states Will Marsh, author of Landscape Planning: Environmental Applications, a classic textbook. Will Marsh came to BC from the University of Michigan-Flint, where he was Chairman of the Department of Earth and Resource Sciences and a Director of the Laboratory for Land and Water Management.

To Learn More:

To download a copy, click on Primer on Rainwater Management in an Urban Watershed Context.

The Course on the ISMP Course Correction comprises eight modules. The Primer provides the technical foundation for Module C – Focus on Stream Health and Watershed Outcomes. To access the ‘homepage’ for the course, click here.

Rainfall spectrum

Posted November 2011