FLASHBACK TO NOVEMBER 2011: Partnership for Water Sustainability released “Primer on Urban Watershed Modelling to Inform Local Government Decision Processes”



Integrating the Site with the Watershed and Stream

ln 2002, the Province released Stormwater Planning: A Guidebook for British Columbia. The Guidebook introduced a number of concepts, including the Modelling Hierarchy. Building on the Guidebook foundation, the Partnership for Water Sustainability in British Columbia released the Primer on Urban Watershed Modelling to Inform Local Government Decision Processes in November 2011.

“The Modelling Hierarchy is about ‘appropriate and affordable’ computer modelling. To help local governments, the Guidebook articulated a guiding principle that the level and/or detail of modeling should reflect the information needed to make informed decisions,” states Jim Dumont, Engineering Applications Authority for the Water Balance Model Partnership.

“By addressing what appropriate and affordable should mean in practice, the Primer deals with two separate dimensions of an Integrated Stormwater Management Plan (ISMP). The first is the Watershed itself, where the focus is on the relationship between rainfall and resulting flow rates in streams. The second is the storm drainage system, where the focus is on infrastructure and the level of service.”


Guidance in Three Areas

The purpose of the Primer is to provide engineers and non-engineers with a common understanding regarding ‘appropriate and affordable’ computer modelling. The Primer elaborates on:

  • Performance Targets:  brings forward a synopsis of key information from Stormwater Planning: A Guidebook for British Columbia
  • Levels-of-Service:explains why and how the major financial challenge resulting from the ‘unfunded infrastructure liability’ is a driver for a life-cycle approach to asset management and renewal
  • Screening / Scenario Tools: introduces the ‘Drainage Infrastructure Screening Tool’ for establishing priorities and making budget decisions for storm sewer system upgrading; and describes the application of the ‘Water Balance Model powered by QUALHYMO’ for establishing watershed-specific performance targets.

From the stream health perspective, appropriate and effective green infrastructure is a way to increase the level-of-service. Expressed another way, green infrastructure that restores the rainfall absorption capacity of the watershed landscape will increase the level of ecological protection.

“For storm sewer systems, the process of establishing an acceptable ‘Level-of-Service’ will require local governments to review, examine, and justify the existing standards and how to transition into the future where costs must be balanced against public needs and expectations,” concludes Jim Dumont.



To download a copy, click on Primer on Urban Watershed Modelling to Inform Local Government Decision Processes.


Posted December 2011