Runoff Ramblings: Trees as Stormwater BMPs

by Karen Cappiella

Spring is (finally) here and as the weather warms up, and watershed groups gear up for Earth Day and Arbor Day, our thoughts turn to planting trees.  One of the most frequent questions the Center is asked related to trees is this: "how much credit should I get for planting trees to reduce stormwater runoff and pollutants?"  Let me just say up front that I don't have a definitive answer, but will try to address this question in true Ramblings form.  Let's break down the question piece by piece:

"How much credit should I get..."

A "stormwater credit" system reduces the stormwater management requirements a developer must meet in exchange for use of an "alternative" (i.e., not on the approved list of BMPs) practice that reduces the volume of runoff (and associated pollutants) generated at the site. For example, many states provide stormwater credits for natural area conservation, impervious cover disconnection, sheetflow to buffers or filter strips, green roofs, permeable pavers and environmental site design. The incentive for using these practices is that they can result in cost savings to the developer by reducing the size of structural stormwater BMPs that must be constructed.  

The most common method to calculate a stormwater credit is to determine how much impervious cover (and therefore runoff and pollutants) is reduced by using the alternative practice and subtract it from the required (water quality and/or recharge) treatment volume.  This approach relies on a simple method of predicting runoff based on land use type. Trees may receive credit for impervious cover reduction because they intercept rainfall that would otherwise reach the ground and be converted to runoff.  The amount of credit given is usually based on:

• The size of the tree (measured as the trunk diameter at breast height): larger trees are given more credit since their larger canopies have a greater rainfall capture ability
• Type of tree: evergreen trees capture rainfall year round and conifers have more foliage surface area compared to deciduous trees, both of which equate to increased rainfall interception
• New plantings versus preservation of existing trees: newly planted trees may only receive 1/3 to ½ of the credit provided for preservation of existing trees because a longer timeframe is needed to realize the stormwater benefits

"for planting trees...."

An important part of the credit system is to define exactly what conditions are eligible for the credit (e.g., will credit be given for planting single trees, or only for reforestation projects?  If a reforestation project, what planting density is sufficient to receive credit?  If a single tree, what species are eligible? Is there a mechanism in place to ensure the trees are planted properly and maintained over time so that they survive long enough to provide stormwater benefits? and so on...).  Most stormwater credit systems provide design criteria and specifications that must be met in order to receive the credit (and hopefully an adequate inspection process to sure these criteria are met). In the case of tree planting, this usually amounts to:

• Trees must be within a certain distance of an impervious surface
• Specifications for tree protection, planting and maintenance must be met (e.g., minimum tree size and spacing, tree planting methods, minimum timeframe for required maintenance)
• An approved species list is typically provided

"to reduce stormwater runoff and pollutants?"

Stormwater credits for trees should reflect the runoff reduction and/or pollutant removal capacity of trees that is documented in the literature.  A tree's combined ability to intercept rainfall, transpire water and increase infiltration ultimately results in runoff reduction, but a complicating factor in quantifying such a credit is that runoff reduction potential varies by the type of tree, size of the canopy and its proximity to an impervious surface.  Rainfall interception alone can vary greatly (across storm events for the same tree) based on the size of a given storm, rainfall intensity, wind conditions and how long it has been since the previous storm event, as well as the time of year (leaf on or off). This complexity can directly conflict with the need for a stormwater credit system to be simple and straightforward so that developers and plan reviewers are not deterred from using it. Similarly, with pollutant removal, it is difficult to assign a single value for removal of a given pollutant because of the variability in pollutant removal mechanisms and influence of individual tree characteristics. Most credit systems use runoff reduction as a proxy for pollutant removal.

Municipalities are increasingly including credits for trees in their stormwater manuals, yet few document how exactly the credits were calculated.  In addition, no credit is given for newly planted trees unless they are located very close to impervious surfaces. This practice discounts water quality benefits provided by planting trees over (or in lieu of) managed turf. One good example of a credit system that is based on the research is the City of Seattle's Impervious Surface Reduction Credits for trees.  A literature review was commissioned by the City in 2008 in order to determine how to develop the City's tree credit program.  The current credit system was developed based on the literature, and actually provides much lower impervious surface reduction credits than do other cities. One important recommendation in the report that is not reflected in the credit system is to provide stormwater credits for ALL trees, even if not located near impervious surfaces.  The report estimated that evergreen trees planted over impervious surfaces reduce runoff by 27%, while trees over turf reduce runoff by 12%[1].  The City's credit system is as follows:

• Newly planted trees must be a minimum of 1.5 inch caliper
• Trees must be on the approved species list
• The specified tree siting and planting methods must be adhered to
• Trunk center must be within 20 feet of a ground level impervious surface
• Impervious surface reduction credits are as follows:
•  50 ft² for tree for evergreens
•  20 ft² for deciduous trees

For more on Seattle's stormwater credits for trees, see: http://www.seattle.gov/DPD/Publications/CAM/cam534.pdf

In summary, a basic structure does exist for municipalities to provide stormwater credits for trees, although it is not always clear how the credits being provided were developed and it can be difficult to boil down the variable literature values to a simple credit system.  Some additional questions to be answered include:

• What are the current data gaps to quantify runoff reduction and pollutant removal for trees in each region of the country?
• What effect might providing stormwater credits for all newly planted trees have on the amount of turf, forest and runoff created at new development sites?
• Are the existing tree credit programs being utilized?
• How can we determine if these urban trees are really providing the benefits they received credit for?

Does your community provide stormwater credits for tree planting? Are you conducting research to quantify the stormwater benefits of trees?  Email us at rambler@cwp.org

Shade Coffee Roundtable in Puerto Rico Provides Momentum for Local Next Steps

by Sadie Drescher 

A pilot project for watershed planning in Puerto Rico is well underway through on-the-ground efforts outlined in the Guánica Bay Watershed Management Plan (CWP, 2008) with a multi-stakeholder approach. A central problem in the Guánica Bay watershed is the high sediment load to the waterways and coral reefs. Upland erosion in the coffee growing regions was identified as a land based source of pollution where steep slopes, high tropical rainfall patterns, and highly erodible lands exist. Converting from sun grown coffee to shade grown coffee keeps the sediment on the farms and off the coral reefs. Early successes in the Guánica Bay to convert to shade grown are ongoing but several obstacles still exist to ensure shade grown coffee growers are economically successful.

To discuss the shade grown coffee obstacles and develop solutions a Shade Grown Coffee Roundtable convened March 9^th in Yauco, Puerto Rico. This roundtable had several partners that included the Center for Watershed Protection, Inc. (Center), US Department of Agriculture-Natural Resources Conservation Service (USDA-NRCS), NOAA Coral Reef Program, NOAA Habitat Restoration Center, and US Fish and Wildlife Service (USFWS), and was funded by National Fish and Wildlife Foundation (NFWF). The goals of the Shade Grown Coffee Roundtable were to: 1) assist farmers in Puerto Rico growing shade grown coffee to improve marketing and a receive a higher premium and return for their products; 2) bring together a group of experts and farmers to convene a discussion about how to the achieve the above; and 3) identify domestic/Puerto Rico coffee markets as well as international and Caribbean markets.

Twenty-three attendees gathered in the Yauco hills at Mr. Luis Roig's farm. Mr. Louis Meyer Comas welcomed the group and discussed the importance to gather farmers, state agencies, federal agencies, and local non-profits to share ideas and develop solutions. Roberto Viqueira Rios (Guanica Restoration Coordinator) and Silmarie Padron (USFWS) provided an overview of the watershed efforts and shade coffee initiative. Then three break out groups were formed to discuss: 1) Marketing and Distribution; 2) Infrastructure and Equipment; and 3) Certification. During the break out sessions at least one of the facilitators joined each group. For each of the three main discussion topics the groups considered the  current state of affairs, existing obstacles, and potential solutions.

The entire Roundtable came back together and one representative from each group reported the findings and summary statements. Based on these results we found that shade grown coffee can be more prevalent in Puerto Rico with improved incentives, a certification process, improved access to labor and equipment, and improved economic markets for farmers and their product. The Roundtable identified the need for farmer cooperatives that enable sharing equipment, labor, information, and enable higher marketing potential. This Roundtable also called for a "Certification Board" that is made up of core local stakeholders and will begin to develop shade coffee certification guidelines, procedures, and a shade coffee label. Furthermore, funding mechanisms were discussed at the Roundtable and the group is moving to pursue these and identify additional mechanisms to achieve the Roundtable recommendations. In addition, the Center and USFWS will present these findings and needs to the NRCS State Technical Committee in early April.

The Shade Coffee Roundtable met to not only sample local shade grown coffee but also develop the first steps to identify stakeholder groups, discuss obstacles and solutions, and create a list of tangible actions and responsible parties to achieve the group's collective goals. 

Group 3 break out session. Picture includes (from left to right) Department of Agriculture representative, Roberto Viqueira Rios (Guanica Restoration Coordinator), Pedro Bengocha (local farmer in the Castañer area), and Lisette Fas-Quinones (Cafi Esencia).

Healthy Harbors, Healthy Neighborhoods: A Plan to Make Baltimore Harbor Fishable and Swimmable by 2020

by Bill Stack  

With funding from the Waterfront Partnership of Baltimore City, Inc., a non-profit organization comprised of key property owners and business adjacent to Baltimore Harbor, the Center for Watershed Protection is developing a "Healthy Harbors, Healthy Neighborhoods" plan to make the Inner Harbor fishable and swimmable by 2020. The work was initiated in October 2010 with a draft plan to be released in May 2011 with the help of Biohabitats, Inc.  

The plan will focus on the Middle and Northwest Branches of the harbor and its tributary streams and will identify major sources of trash, bacteria, nutrients, and sediment. The plan will attempt to define and quantify how much pollution has to be reduced in order for the harbor and its tributaries to be considered clean. Part of the plan will include an evaluation of successful restoration efforts from other parts of the country and how they might be applied in the Baltimore region.

Middle Branch. Photo credit: Alan Cressler, USGS

The core of the plan will build upon the numerous regulatory structures under the Clean Water Act[1] which include provisions to address sewage overflows, sediment and stormwater from development, non-point source pollution from storm drains (MS4 permits) and standards for the restoration of the Chesapeake Bay.  These regulations affect the different municipalities that drain to the Harbor and while they have achieved moderate success, historically they have been managed and implemented without effective coordination. The key to the plan is to work with the managers that administer these programs and identify synergies within the regulatory framework that can more effectively lead to meeting the goals of a clean harbor.  

The plan will include focusing on existing programs to eliminate sanitary sewer overflows. Baltimore City and County are investing millions of dollars to improve the sanitary sewer infrastructure. Ensuring that these programs are coordinated across jurisdictions and with other programs (MS4) that are working to eliminate bacteria and nutrients from storm drains is one of the foundations of the plan.   

Clearly, local government agencies can't accomplish cleanup goals alone. The harbor and its tributaries are affected by the actions of individuals, homeowners, businesses - all the people who live and work in the metropolitan region. The plan to clean up the Harbor and the tributaries will describe the actions needed by both the government sector as well as the private sector. For example, the plan will include recommendations on how and where trash can be reduced; where opportunities exist for greening neighborhoods; and strategies for reducing nutrients and bacteria in voluntary ways.  

As part of the plan, a database is being developed that will display spatially the many opportunities for watershed restoration activities. Most of these opportunities have been identified in watershed management plans developed under local MS4 permits.  This database will include highly visible waterfront best management practices that serve to demonstrate and educate, as well as places where stream restoration projects are needed. It will also quantify opportunities to retrofit specific locations within the urban landscape: public rights of way, institutions, open space, commercial lands, vacant properties, residential neighborhoods and the storm drainage system. In all cases, specific ideas for pilot projects will be included in the plan.

Fundamental to a successful plan is quantification of the environmental benefit of each suggested action. For each type of pollutant, the plan will provide in matrix format the specific practices that can be employed and what the benefits as well as the costs of each would be. It will also lay out a recommended schedule and milestones for measuring progress toward the ultimate fishable, swimmable goal.  

Because the costs of cleaning up the harbor are not insignificant, the plan will describe potential funding strategies including the creation of a new stormwater fee, and it will make recommendations on how municipalities can select restoration practices that are not only cost effective for pollutant removal but also provide benefits to neighborhoods such as greening and beautification. The plan will allow for public input throughout the implementation process. The advice, suggestions and commitment of citizens to "make it happen" will be essential to success.

Center Launches the Wetlands-At-Risk Protection Tool (WARPT) Website 

by Lisa Fraley-McNeal 

Nominate a Watershed Superstar!

Coastal Zone 2011

July 17-21, 2011, Chicago, IL

The Call for Abstracts has been issued for the Coastal Zone 2011 Conference. The overall conference theme is Winds of Change: Great Lakes, Great Oceans, Great Communities. Sessions will be organized around four conference tracks: Planning for Resilient Great Lakes, Coasts, and Ecosystems; Healthy Habitats, Healthy Coastal and Great Lakes

Communities; Observing, Modeling, and Monitoring; and Vibrant Coastal, Great Lakes, and Marine Economies.

Website: http://www.doi.gov/initiatives/CZ11/index.htm 

Philadelphia Low Impact Development Symposium:  Greening the Urban Environment

September 25-28, 2011.  Philadelphia, PA

This symposium serves to combine three annual events into a single venue:  5^th National Low Impact Development Conference, 19^th Annual National Non-Point Source Monitoring Workshop, and the 2011 Pennsylvania Stormwater Management Symposium.  Registration will open on Sunday afternoon, Sept. 25, followed by pre-conference workshops. The three-day technical program, Monday - Wednesday, will include six concurrent tracks.  Greg Hoffmann, Watershed Engineer with the Center, will co-present a paper on recent stormwater retrofitting endeavors in Arlington County, VA.

Website:  http://www.bae.ncsu.edu/stormwater/2011lid/index.html

International Forum: Stormwater Management in Urban - Call for Speakers  

October 23-25,2011, Quebec, Canada 

This conference will be held from October 23-25, 2011 at the Cultural Center of the University of Sherbrooke (Québec, Canada). Speakers and participants from all the stormwater management sectors will be invited to present practical tools, to share experiences to create new partnerships.

Professionals from municipalities, universities, watershed organizations, engineering firms, environmental organizations, developers and investors are invited to respond to the call for speakers and posters to present a paper concerning one of the major themes:

• Governance, strategy development and territorial planning
• Assessment of innovative stormwater sewage and harvesting techniques
• Modeling tools
• Stormwater management in watershed scale

AWSPs members receive a special savings of 70% off conference registration fees.

Website: http://www.rv-eau.ca/index.php/en

Cool Links

"Cool Links" provides information on some new or new-found resources that are helpful to watershed managers and stormwater professionals.

ChesapeakeView

ChesapeakeView is a collaborative project of the AmericaView program. AmericaView (AV) is a nationwide program that focuses on satellite remote sensing data and technologies in support of applied research, K-16 education, workforce development, and technology transfer. ChesapeakeView is about free access to data about the Bay Region. It is the first regional AmericaView initiative. The purpose of the ChesapeakeView project is to facilitate access to remotely sensed data as well as habitat, land use, biodiversity, and other types of data related to the Chesapeake Bay region. This effort seeks to highlight the data resources of the AmericaView partners in the Chesapeake Bay region including Maryland, New York, Pennsylvania, Virginia, and West Virginia as well as other organizations that create data related to the bay. Any organization--government agency, academic institution, nonprofit, watershed association, etc. with data about the bay can share it through ChesapeakeView. There is no charge for this service and all data is publicly available.

http://www.chesapeakeview.psu.edu/ 

Green Infrastructure Valuation Guide

A new report by the Center for Neighborhood Technology and American Rivers quantifies the economic value of green infrastructure. This guide distills key considerations involved in assessing the economic merits of green infrastructure practices. It examines the steps necessary to calculate a variety of performance benefits gained by implementing GI strategies and then, where possible, demonstrates simplified illustrative examples that estimate the magnitude and value of these benefits.    

http://www.cnt.org/repository/gi-values-guide.pdf 

The Value of Green Infrastructure for Urban Climate Adaptation

The Center for Clean Air Policy has just released a report about the costs and benefits of "green" infrastructure solutions for bolstering local adaptation to climate change. This report will evaluate the performance and benefits of a selection of green infrastructure solutions, using their range of technological, managerial, institutional, and financial innovations as a proxy for their value for climate adaptation.

http://www.ccap.org/docs/resources/989/Green_Infrastructure_FINAL.pdf 

BMP and LID Whole Life Cost Tools

In partnership with the U.S. Environmental Protection Agency (U.S. EPA), WERF has developed a new suite of tools to address the costs associated with vegetative roofs, rainwater catchment systems, and bioretention facilities. These tools provide a framework to facilitate cost estimation for capital costs, operation and maintenance costs, and life-cycle net present value. The tools can serve as a format for cost reporting for past, current, and future projects. They also provide users with planning-level cost estimates. These tools complement an existing suite of BMP whole life cost models for retention ponds, extended detention basins, swales, and permeable pavement developed under a previous WERF project. To access the complete set of tools and accompanying user's guide, visit

www.werf.org/bmpcost 

Bay 101: Healthy Forests

Forests once covered nearly all of the Chesapeake Bay watershed. They're critical to our region because they provide habitat and help clean our air and water. Learn all about the importance of forests and the features of a healthy forest in our latest "Bay 101" video. Watch video:

http://vimeo.com/17851496 

EPA has just published a Draft Healthy Watersheds Technical Document

Several years in the making, this draft document was developed to help implement the Healthy Watersheds Initiative by providing EPA, state, tribal, and local practitioners with an overview of the key concepts behind the Healthy Watersheds approach, examples of assessments of healthy watershed components, an integrated assessment framework for identifying healthy watersheds, examples of management approaches, sources of national data, and key assessment tools. It contains numerous examples and case studies from across the country.

The intended audience for this document is aquatic resource scientists and managers at the state, tribal, regional, and local levels; nongovernmental organizations; and federal agencies. It will also benefit local government land use managers and planners as they develop protection priorities. EPA is seeking comments on this draft document until June 3, 2011. It will also undergo a scientific peer review. A final version of this document is expected by October 2011 and will be posted on this web page.  The document may be reviewed at

http://water.epa.gov/polwaste/nps/watershed/index.cfm  

Please send any comments to hwcommentshq@epa.gov