Re-Inventing Urban Hydrology – Going Back to Basics to Develop New Tools

Drainage engineers have traditionally thought in terms of flow rates, not volumes. In dealing with urban hydrology, we need to focus on how much rainfall volume has fallen, how we are going to capture it, and what we are going to do with it. The volume-based approach that is being implemented in British Columbia picks up the baton that Dr. Ray Linsley (started more than a generation ago. As a professor of Civil Engineering at Stanford University, and later as a consulting engineer, Linsley pioneered the development of continuous hydrologic simulation as the foundation for water balance management. For the past thirty years, there has been a fixation on peak flow control through the use of detention ponds for all flood events from the 2-year through 100-year floods, and the conveyance of major flood events caused by urban developments of all kinds. The recently developed software focus has been on the user interfaces, but not on the hydrology engine; and certainly not on improvements in the science of infiltration. The missing link in urban hydrology has been a tool that quantifies the benefits, in terms of reducing stormwater runoff volume at the site level, of installing source controls under a variety of circumstances. In British Columbia, the water balance modeling approach was developed to demonstrate how to meet performance targets for water balance management at the site, neighbourhood, drainage catchment, and watershed scales.

Author Kim A Stephens & Thomas N. Debo, PhD.

Publisher FreshOutlook Magazine

Date February 2003