WHOLE-SYSTEM, WATER BALANCE TRAINING FOR ENGINEERS: “The Town’s experience is that the weak link in drainage analyses is always the assumptions,” stated Shelley Ashfield, Municipal Engineer, when she explained why the Town of Comox took on responsibility for an educational process to bridge a gap in practitioner understanding
Note to Reader:
In September 2019, the Partnership for Water Sustainability in British Columbia released the 8th in the Watershed Case Profile Series. It features the Town of Comox, and the Brooklyn Creek Watershed Society, in the Comox Valley region of Vancouver Island.
Storylines touch lightly on technical matters, yet are grounded in a technical foundation. The objective in ‘telling a story’ is to engage, inform and educate multiple audiences – whether elected, administrative, technical or stewardship. Stories in the series are presented in a magazine style to make it easier to read, comprehend and absorb technical information. Stories are designed to connect dots.
DOWNLOAD: Comox-Beacon of Hope_Sep2019
A Beacon of Hope
“British Columbia is at a tipping point. Will local governments bridge the gap between policy and new standards of practice, reconnect hydrology and ecology, create greener communities, and adapt to climate change?,” wrote Kim Stephens, Partnership Executive Director, in the preface to Town of Comox – A ‘Beacon of Hope’ for Citizen Science in Action & Reconnecting Hydrology and Ecology through the Water Balance Approach to Land Development.
“The Partnership for Water Sustainability has identified Comox as a beacon of hope because the Town’s experience shows what is possible when a local government has a strong working relationship with the stewardship sector, and leads by example to implement responsible water balance management.”
Northeast Comox Land Development
“The Town of Comox has established a provincial precedent in truly applying a whole-system, water balance approach to land development in Northeast Comox. The break from historical drainage engineering practice dates back to April 2012 when Council approved Terms of Reference for a North East Comox Storm Water Management Plan,” continued Kim Stephens.
“Over the past seven years, an approach has taken shape that follows the direction provided by Stormwater Planning: A Guidebook for British Columbia, released by the provincial government in 2002. The Guidebook introduced the Water Balance Methodology as a way to set performance targets for reducing runoff volume and mimicking the natural flow patterns in streams, and so protect property and habitat.” Kim Stephens was project manager and principal author of the Guidebook.
Prior to release of the Guidebook in 2002, provincial government lawyers completed a review of BC case law for the Steering Committee. Their review prompted inclusion of this statement in the Guidebook about liability for downstream impacts due to changes in the water balance: These (three) cases underscore the responsibility of local government for stormwater volume management.
”In 1990-1991, the BC Court of Appeal upheld three decisions that found municipalities liable for lowland nuisance flooding caused by upland urbanization,” recalls Peter Law, Guidebook Chair.
“Upon reading those judgments, it was clear that the judges grasped that it was a runoff volume issue. In retrospect, however, something got lost in the translation afterwards. Instead of volume, the engineering profession focussed on controlling peak flow rates through detention ponds. Two decades after release of the Guidebook, refocussing engineers on true water balance management is still problematic.”
The Challenge: Bridge an Educational Gap
How water gets to a stream, and how long it takes, is not well understood among land and drainage practitioners. The flow of rainwater from cloud to stream is comprised of three water balance pathways: surface runoff, horizontal shallow interflow, and deep groundwater (aquifer discharge). Yet the latter two are routinely ignored by designers. Time, a critical factor, is also ignored.
Engineering practice for servicing of land still relies on very simple formulae and methodologies to calculate peak rates of surface runoff. Thus, it is reasonable to conclude that failure by designers to grasp and apply the science-based fundamentals of a water balance approach is perpetuating degraded urban streams.
When it rains – there is too much runoff, too fast. When there is no rain, there is too little streamflow. The consequences are: more flooding; more stream erosion; and less streamflow when needed most.
“The Town’s experience is that the weak link in drainage analyses is always the assumptions,” states Shelley Ashfield, Town of Comox Municipal Engineer.
“A lack of explicit identification and justification of the assumptions and simplifications made in the analysis of stormwater impacts has resulted in stormwater systems that address hypothetical as opposed to actual site characteristics and development impacts.
“Learning from this experience, the Town now requires that assumptions be stated and explained. We are saying WHAT is your assumption, and WHY.”
Whole-System, Water Balance Training for Engineers
Opening minds to accept changes in practice is challenging, especially when there is no direct regulatory (prescriptive) requirement at the provincial level. This reality meant the NE Comox situation called for an educational process to bridge a gap in practitioner understanding.
So, Shelley Ashfield took on the responsibility, and organized a training course for local drainage and land development engineers. Taught by Jim Dumont, the course comprised six sessions over a 3-month period. 20 individuals attended. Voluntary participation required a major commitment of their time. The Town also extended the invitation to attend to all local governments on Vancouver Island.
“The Town hosted this training because the planning and design process is becoming increasingly more complex, and with greater expectations than we have ever applied to drainage infrastructure. The course was a major undertaking,” reports Shelley Ashfield.
“It has taken a huge investment of effort and collaboration between the Town and local development engineers to: (1) realize and then understand the different constraints, requirements and abilities of each party; and (2) collaborate in the creation of a new approach to rainwater management. The result is an approach where assumptions and simplifications are understood by both parties and where there is mutual agreement as to their applicability to development site characteristics and the rainwater management objectives.”
To Learn More:
For the story of the presentation by Kim Stephens to Comox Town Council, read URBAN DESIGN & THE PACKAGE OF ECOLOGICAL SERVICES: “The ‘Comox story’ is indeed a blueprint for what the phrase hard work of hope means in practice,” stated Kim Stephens, Partnership for Water Sustainability, when he met with Comox Town Council to present the 8th in the Watershed Case Profile Series (September 2019)
The ‘table of contents’ presented below is a synopsis of the ‘Comox story’. It distills the essence of each section into a succinct statement. These create a storyline. When reading this synopsis, readers should pause and reflect on the messages before continuing.