Comox. Valley A. Rainwater Benefits. Six

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1 Comox Valley Local Governments Showcase A Regional Response to Infrastructure Liability Rainwater Management in a Watershed Context: Do More With Less & Achieve Stream Health Benefits Six in a series published on the Water Bucket Websitee May 20111

2 2011 Comox Valley Learning Lunch Seminar Series A Regional Response to Infrastructure Liability Rainwater Management in a Watershed Context: Do More With Less & Achieve Stream Health Benefits. Preface 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 information 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 opposite. Kim A. Stephens, MEng, PEng, Executive Director Partnership for Water Sustainability in British Columbia May 2011 Organized under the umbrella of the Water Sustainability Action Plan for British Columbia By the CAVI-Comox Valley Regional Team

3 2011 Comox Valley Learning Lunch Seminar Series A Regional Response to Infrastructure Liability Rainwater Management in a Watershed Context: Do More With Less & Achieve Stream Health Benefits Organized under the umbrella of the Water Sustainability Action Plan for British Columbia By the CAVI-Comox Valley Regional Team

4 2011 Comox Valley Learning Lunch Seminar Series A Regional Response to Infrastructure Liability Rainwater Management in a Watershed Context: Do More With Less & Achieve Stream Health Benefits Comox Valley Local Governments Showcase A Regional Response e to Infrastructure Liability Through a program of continuing education, the four Comox Valley local governments are aligningg efforts, building leadership capacity, and striving for consistency at their front counters. A focus of the 2011 Series is on why and how all those involved in land development have a role to play in achieving Sustainable 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: Paying down the 'legacy cost' of existing hard infrastructure (i.e. roads, water, sewer). This is not going away. It must be addressed. Financing the life-cycle cost of new hard infrastructure (water and sewer) that serves new development. 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 shift from gray to green is captured in the working definition of Sustainable Service Delivery. 1 Organized under the umbrella of the Water Sustainability Action Plan for British Columbia By the CAVI-Comox Valley Regional Team

5 2011 Comox Valley Learning Lunch Seminar Series A Regional Response to Infrastructure Liability Rainwater Management in a Watershed Context: Do More With Less & Achieve Stream Health Benefits 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 achievee more with less. Sustainable Drainage Infrastructure The paradigm-shift starts with land use planning. Connecting the dots between watershed healthh and infrastructure type is emerging as an important piece in sustainable drainage infrastructure, both fiscally and ecologically. 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 floodd 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, floodd protection, ecological integrity AND cost. Everyone will have to make level-of-service principle for a choices. Thus, a guidingg watershed-basedd plan could be framed this way: Establish the level-of-service that is fiscally sustainable AND protects watershed health," states Jim Dumont. 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-basehave lower life-cycle costs, decrease stressess applied to creeks, and enhance urban assets reduce runoff volumes, livability. 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. Twoo complementary strategies can green a community and its infrastructure: preserve and protect naturall green infrastructure; and implement designs that soften the footprint of development. 2 Organized under the umbrella of the Water Sustainability Action Plan for British Columbia By the CAVI-Comox Valley Regional Team

6 2011 Comox Valley Learning Lunch Seminar Series A Regional Response to Infrastructure Liability Rainwater Management in a Watershed Context: Do More With Less & Achieve Stream Health Benefits 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. "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," statess 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. Jim Dumont will speak to this topicc at Seminar #2 on May 19. Refer to the handout that follows. This presents the methodology for establishing science-based targets. 3 Organized under the umbrella of the Water Sustainability Action Plan for British Columbia By the CAVI-Comox Valley Regional Team

7 Partnership for Water Sustainability in British Columbia Beyond the Guidebook: Water Balance Model powered by QUALHYMO One of the tools developed under the umbrella of the Water Sustainability Action Plan is the Water Balance Model for British Columbia. Developed by an Inter-Governmental Partnership (IGP) as an extension of Stormwater Planning: A Guidebook for British Columbia, the Water Balance Model enables users to visualize how to implement green infrastructure solutions that achieve rainwater runoff source control at the site scale. The Guidebook's premise that land development and watershed protection can be compatible represented a radical shift in thinking in The Guidebook recognized that water volume is something over which local government has control through its infrastructure policies, practices and standards. Beyond the Guidebook is an initiative that builds on this foundation by advancing a runoffbased approach and tool the Water Balance Model powered by QUALHYMO to help local governments achieve desired urban stream health and environmental protection outcomes at a watershed scale. May 15, 2011

8 Hydrologic Impact Assessment 1. Use continuous simulation to assess the mass balance of rainfall, runoff, infiltration and evaporation. 2. Graphically represent the mass balance analysis. 3. Use the continuous simulation to estimate discharge exceedances. These would be the values of runoff plus groundwater return to the system. 4. Present results of flow exceedance analysis results in tabular or graphical format. 5. Use BMP s to achieve the desired objectives. Mass Balance (mm) Mass Balance Analysis Infiltration Total Rainfall Runoff Surface Evaporation Establish Targets Two methods can be used to establish targets used for design of runoff volume reduction systems and facilities. 1. Use the volume of runoff from redevelopment or existing watershed conditions, or 2. Use the stream flow duration and exceedance analysis combined with the stream erosion potential to establish discharge rate and volume targets. Test and optimize the size and the operation of the runoff volume reduction systems and facilities in the watershed to achieve the desired objectives and targets. 0 Period of rainfall record 1982 through Percent Impervious Flow Exceedance Analysis Pre-Development Total Hours of Exceedance (hrs) Loss of Base Flow Post Development Post-Development Partial BMPs Post Development Full BMP's Discharge (cms) Hydrologic Change Assessment

9 Steps in the stream assessment 1. Estimate the Tractive Force applied to the stream bed and banks for a range of discharge values. 2. Estimate the critical tractive force below which erosion will not occur. Use only the tractive forces in excess of the critical in the next steps. 3. Use the continuous simulation to estimate the duration of discharge for a range of occurring stream flows. 4. Estimate the Impulse by applying the discharge and estimating the tractive force applied at the section over the duration of the simulation. The impulse is the sum of the tractive force over time Tractive Force = Rs, where = unit weight of water R = hydraulic radius of flow, and s = slope of channel Impulse I = ( PT), where = Tractive Force P = wetted perimeter T = time 5. Present results for different watershed conditions or runoff volume reduction system alternatives in tabular or graphical format. Erosion Assessment Site Total In-stream Impulse (kn.h/m) Pre-Development Post- Development 43.9 Post- Post- Development w/ Development w/ Partial BMP Full BMP Stream Impact Assessment

10 WBM Model Process Diagram Rainfall Evaporation Possible Evaporation Can add in detention ponds Catchment To Ground Runoff Surface Changes Hydrologic Model Detention / Infiltration System Overflow Underflow Stream To Ground Volume and/or Rate Control Hydraulic Model Modelling Surface Changes - Hydrologic Model Mitigation with Absorbent Landscapes Tree cover density Increased top soil depth Porous pavement Green Roof Typical Some infiltration swales without storage Modelling Runoff Reduction - Hydraulic Model Capture surface runoff and STORE it for infiltration to reduce discharge volume Rain gardens with storage Infiltration swales with storage Surface or subsurface storage Infiltration ponds Underground galleries