Rainwater Management in a Watershed Context: "Do More With Less & Achieve Stream Health Benefits"



Note to Reader:

The unifying theme for the 2011 Comox Valley Learning Lunch Seminar Series is: A Regional Response to Infrastructure Liability. At the conclusion of the 2011 Series, the four local governments will prepare a Joint Report on a policy framework for resolving the unfunded infrastructure liability.

The initial capital cost of infrastructure is about 20% of the life-cycle cost; the other 80% largely represents a future unfunded liability. This is a driver for local governments in the Comox Valley to change the way they plan, finance, implement and over time replace infrastructure. 

In addition, local governments bear the entire financial burden to stabilize and restore watercourses impacted by the cumulative impacts of increased rainwater runoff volume after land is initially developed or redeveloped to a higher density.

The purpose of the article that follows is to foreshadow what Jim Dumont will present at the second seminar in the 3-part series. He will deliver a short course on Rainwater Management. This encompasses History-Science-Tools. He will:

  • describe how our understanding of drainage impacts has evolved over the past two decades;
  • explain how to establish science-based performance targets for rainfall capture and runoff control; and
  • introduce inexpensive screening tools that provide relevant infornation for capital planning, and without having to do detailed and expensive computer simulation of the drainage system.

The scope of the 2011 Series is encapsulated in the image below. To download a PDF copy, click on the 2011 program at a glance. To download a PDF version of the article below, click on Rainwater Management in a Watershed Context: Do More With Less & Achieve Stream Health Benefits.




Comox Valley Local Governments Showcase ‘A Regional Response to Infrastructure Liability’

Through a program of continuing education, the four Comox Valley local governments are aligning efforts, building leadership capacity, and striving for consistency at their front counters. A focus of the the 2011 Series is on why and how all those involved in land development have a role to play in achievingSustainable Service Delivery.


Sustainable Service Delivery

Town Hall Sharing Sessions are an important part of the seminar program. At the conclusion of Seminar #1, an ‘Ah-Ha’ moment was a realization of the need to communicate that there are three dimensions to infrastructure liability and hence Sustainable Service Delivery:

  1. Paying down the ‘legacy cost’ of existing hard infrastructure (i.e. roads, water, sewer). This is not going away. It must be addressed.
  2. Financing the life-cycle cost of new hard infrastructure (water and sewer) that serves new development.
  3. Shifting from gray to green in order to mitigate downstream drainage risks and not incur downstream drainage costs.

The focus of Seminar #2 is on the third dimension. The phrase ‘gray to green’ is becoming part of the language. Viewed from space, the urbanized landscape appears to be mostly gray. This reflects the impact of roads, rooftops and paved surfaces. The need to shiift from gray to green is captured in the working definition of Sustainable Service Delivery.


Rainwater Management in a Watershed Context: Shifting from Gray to Green

As infrastructure ages and fails, local governments cannot keep up with renewal and/or replacement. Thus, fiscal constraints provide a powerful impetus for doing business differently. Green infrastructure is part of a holistic approach to ‘achieve more with less’.


Sustainable Drainage Infrastructure

The paradigm-shift starts with land use planning. Connecting the dots between watershed health and infrastructure type is emerging as an important piece in ‘sustainable drainage infrastructure’, both fiscally and ecologically.

“The need to embrace green infrastructure practices arose from the requirement to prevent further increases in damage to both the environment and the agricultural community resulting from the increase in rainwater runoff from urban areas,” states Jim Dumont, Engineering Applications Authority for the Water Balance Model Partnership.

“The financial burden and environmental impacts associated with ‘pipe-and-convey’ drainage infrastructure contrast with the benefits of ‘green’ infrastructure at a watershed scale: natural landscape-based assets reduce runoff volumes, have lower life-cycle costs, decrease stresses applied to creeks, and enhance urban liveability.”


Make Level-of-Service Choices

‘Level-of-Service’ is the integrator for everything that local governments do. For drainage infrastructure, it refers to the expected level of performance of municipal systems in providing flood protection. What level of service does a community wish to provide, and what level can it afford?

“There are trade-offs between drainage of land, flood protection, ecological integrity AND cost. Everyone will have to make level-of-service choices. Thus, a guiding principle for a watershed-based plan could be framed this way: Establish the level-of-service that is fiscally sustainable AND protects watershed health,” states Jim Dumont.


Doing Business Differently

The Province’s Living Water Smart and Green Communities initiatives are a catalyst for doing business differently: Start with effective green infrastructure and restore environmental values within the urban fabric over time. Actions and targets in Living Water Smart encourage ‘green choices’ that foster a holistic approach to infrastructure asset management.

Two complementary strategies can ‘green’ a community and its infrastructure: preserve and protect natural green infrastructure; and implement designs that soften the footprint of development.


Water Balance Model Compares Scenarios

The Water Balance Model is a tool in the toolbox for the Living Water Smart and Green Communities initiatives. At Seminar #2, Jim Dumont will explain the application of the Water Balance Model (WBM). This is a scenario modelling and decision support tool. It is accessible to multiple levels of users who have a wide range of technical backgrounds, from hydrology experts to stewardship groups.

WBM powered by qualhymo (120p)“The WBM allows comparison of multiple scenarios of watershed condition using historical climate data. This supports the design of communities that have no net impact on stream environments. The WBM web interface is powered by the QUALHYMO engine which does the hydrologic and hydraulic calculations,” states Jim Dumont.

In November 2009, the Water Balance Model Partnership released its road map document titled The Plan for the Future. The Town of Comox and CIty of Courtenay are members of the Partnership.


How to Set Performance Targets

The Water Balance Model enables the user to establish performance targets for rainfall capture and runoff control at the site, neighbourhood and watershed scales. To learn more, click on Beyond the Guidebook: Methodology for Establishing Science-Based Performance Targets. Jim Dumont will speak to this handout at Seminar #2 on May 19. 


To Learn More:

Click on Inter-Provincial Partnership names Jim Dumont as the Engineering Applications Authority for the Water Balance Model — Responsibilities encompass hydrology applications and stream health methodologies that enhance use of the WBM as a scenario modeling and decision support tool at the site, neighbourhood and watershed scales.

Click on British Columbia Moves Beyond 90% Rainfall Capture Target Proposed by United States EPA — At the end of the day it is how effectively we apply the suite of available rainwater management tools that will ultimately determine whether we will succeed in protecting stream health.

Click on Water Balance Model can create an understanding of the past and compare it to many possible futures — A key message is that the Water Balance Model is a ‘scenario comparison tool’. There is no restriction on the scenarios that a user may choose to compare.

Click on Partnership announces that Water Balance Model “Version 2.1” will go live in Fall 2011 — “We’ve reached a point where one WBM interface no longer works for everyone. We now need to provide an environment that supports communities that range from highly experienced experts to enthusiastic newcomers.” (Dr. Charles Rowney, WBM Scientific Authority, APril 2011.


Posted May 2011