Released in 2002, ‘Stormwater Planning: A Guidebook for British Columbia’ has proven to be a catalyst for action
The Goal – Protect Stream Health
In BC, 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.
Impact of the Salmon Crisis
Looking back, the salmon crisis of the 1990s was the catalyst for action. The salmon is an icon. It is also the early warning system that there is a problem. Coastal salmon runs such as Coho, chum and pink spawn and rear in the headwater streams which are typically small. A generation ago, the ecosystem value of headwater streams was not fully appreciated. The result: streams were being lost as a consequence of rapid population growth and land development.
The lack of understanding and respect contributed to the decline of many wild salmon populations. And so the goal of protecting stream health became a driver for action in BC.
Science-Based Understanding Informs Policy and Practice
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 Environment Canada and two Ministries – Environment and Municipal Affairs. The process produced a science-based framework to guide development of the rainwater (stormwater) component of Liquid Waste Management Plans.
The core premise of the Guidebook is that land development and watershed protection can be compatible. This also suggests that urban watershed restoration is achievable over time. The Guidebook signified a paradigm-shift. This resulted from recognition of HOW a science-based understanding could bridge the gap between high-level policy objectives and site design practices.
“The Guidebook applied a science-based understanding, developed the water balance methodology to establish performance targets, and demonstrated that urban watershed restoration could be accomplished over a 50-year timeframe as and when communities redevelop,” states Peter Law. Chair of the Guidebook Steering Committee (2000-2002). Formerly with the Ministry of Environment, Peter Law is a founding Director of the Partnership for Water Sustainability in British Columbia.
“The premise underpinning the Guidebook was that land development and watershed protection can be compatible. The basis for this premise was that municipalities exert control over runoff volume through their land development and infrastructure policies, practices and actions.”
Look at Rainfall Differently
A decade ago, looking at rainfall differently led the Province of BC to develop the Water Balance Methodology, and initiate a paradigm-shift in the way rainwater is managed. The Province:
Formalized the performance target methodology in Stormwater Planning: A Guidebook for British Columbia, a provincial guidance document released in 2002.
Translated science-based understanding so that local governments could establish achievable and affordable performance targets for rainfall capture and runoff control.
BC was the first provincial or state government in North America to implement the Water Balance Methodology.
From Stormwater to Rainwater
The Guidebook was the catalyst for moving from the extreme storm view embodied in conventional ‘Stormwater Management’ to the integrated, holistic and landscape-based perspective that is embodied in ‘Rainwater Management’. In 2002, the Guidebook also set the stage for defining water sustainability as an outcome of green infrastructure policies and practices. This followed four years later in 2006.
The comparison below captures the evolution of drainage planning in BC between 1970 and 2002. The move to volume-based practice was made possible by the Water Balance Methodology.
Water Balance Methodology
The Water Balance Methodology is founded on the concept known as the Rainfall Spectrum: the methodology accounts for all the rainfall-days in a year; and links rain that falls on a site…to the runoff leaving the site…to the flow in a stream.
Reproduced from the Guidebook, the image below illustrates the elements comprising the Integrated Strategy for Managing the Rainfall Spectrum. Water gets to a stream in one of three ways: surface runoff, shallow groundwater (interflow), and deep groundwater.
The Rainfall Spectrum is a universal relationship. In other words, the number of rainfall-days and the total rainfall volume per year may vary by region, but the distribution of that volume has a consistent pattern.
Evolution of the Methodology: The Water Balance Methodology is dynamic; and it is being enhanced over time to incorporate fresh insights resulting from science-based understanding. A key goal is to improve the technical basis for local government decisions. Three milestones in the evolutionary process are introduced below:
First, in 2002, the Guidebook integrated hydrology and aquatic ecology. This built on Washington State research findings about the four factors limiting stream health.
Then, in 2007, the ‘Beyond the Guidebook’ initiative added geomorphology to the mix. This addressed the relationship between volume control and resulting flow rates in streams; and correlated stream health with stream erosion.
Most recently, in 2012, the understanding yielded by the Englishman River research on Vancouver Island has added a groundwater dimension to stream health.
The Water Balance Methodology is a foundation block for those tasked with developing a Master Drainage Plan, an Integrated Stormwater Management Plan (ISMP), the Rainwater Management Component of a Liquid Waste Management Plan, or a Watershed Blueprint.