Regulatory Context for Rainwater Management in Metro Vancouver Region
Rainwater management is a key component of protecting quality of life, property and ecosystems. This is why, in 2000, Greater Vancouver municipalities signed a regulatory commitment to the Province to fully implement integrated rainwater management policies, plans and practices by 2012.
Well, What is Rainwater Management, Really?
Rainwater runoff is created when land development alters the natual water balance. As trees, vegetation and soils are replaced with bigger and bigger houses, for example, less rainfall volume infiltrates naturally into the ground, less gets taken up by trees and vegetation, and more and more of the rainfall volume becomes runoff.
Land Development and Watershed Protection can be Compatible
In 2002, the Province published Stormwater Planning: A Guidebook for British Columbia. The Guidebook formalized a science-based understanding to set performance targets for reducing rainwater runoff volumes from individual sites. The Guidebook drew heavily on case study experience by leading local governments in Greater Vancouver and other regions. At the heart of the Guidebook is the Water Balance Methodology. The core technical content was provided by the Greater Vancouver Regional District, in particular Chapter 7 (Site Design Solutions for Achieving Performance Targets) and Chapter 8 (Watershed Context for Site Design Solutions).
A Tool for Designing with Nature
Also in 2002, an Inter-Governmental Partnership was formed to develop the web-based Water Balance Model for British Columbia as an extension of the Guidebook. The Partnership began as a subgroup of an inter-agency technical committee of the Greater Vancouver Regional District. It quickly expanded to become a provincial group with municipal representation from four regions. The Partnership recognized that practitioners and others needed an easy-to-use tool so that they could readily calculate annual runoff volumes under different combinations of building coverage, rainfall, soil type and depth, tree canopy coverage, and source controls.
Rainwater Source Control Design Guidelines 2005
To complement the Water Balance Model, Greater Vancouver municipalities commissioned a set of Source Control Design Guidelines for landscape-based solutions – that is, absorbent landscapes, rain gardens, pervious pavers, infiltration swale systems, infiltration trenches and green roofs – for reducing rainwater runoff volumes. Published in 2005, the Guidelines are supplemented by a set of posters that display the results of the applied research. The Guidelines were adapted from design standards from areas of England, Europe, Australia, New Zealand and North America with comparable soil and climate conditions to Greater Vancouver. To download the Design Guidelines and the set of accompanying posters, please click here.
Template for Integrated Stormwater Management Planning 2005
Created in 2002 and finalized three years later, the Template for Integrated Stormwater Management Planning 2005 provides a standardized process that includes all of the key components for rainwater and stormwater management. A municipality can decide which components are applicable, and can establish the level of effort required based on risk and local conditions. The ISMP Template is nested within Chapter 9 of the Guidebook
Research Program will Quantify Rainfall Interception Benefits of the Urban Forest
The Water Balance Model includes a tree canopy module so that the rainfall interception benefits of trees in the urban environment can be quantified. This module was developed at the instigation of the three North Shore municipalities. To populate the module with local data, the Inter-Governmental Partnership and the University of British Columbia have embarked upon an applied research program. The District of North Vancouver is acting on behalf of the Partnership in leading this on-the-ground initiative. For more on this story, please click here.
Posted September 2006