A flood of concern in Roanoke: after an urban ecosystem analysis, officials agree increasing tree cover is the best way to alleviate long-standing problems.

Roanoke, Virginia, sits at the head-waters of three major water systems: the New River on one side of the watershed flows into the Mississippi River, the Roanoke River flows to the Outer Banks, and the Upper James River flows to Chesapeake Bay. Over the years major flooding problems, caused by Roanoke's valley location together with urban development that has increased impervious surfaces, has prompted government officials, private agencies, and citizens to establish efforts that will address the flooding.

The solution centers on trees.

It's an age-old, natural answer to the problems that appear when human development disturbs nature's sense of balance. "The city's founding fathers initially didn't understand the conditions inherent with building at the bottom of a 'bowl,'" says Tom Cain, executive director of Project Impact, an initiative of FEMA (the Federal Emergency Management Agency).

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"One of our approaches is to rethink that," he says. "The city is only about 125 years old. We are really trying to get to a large-scale cultural understanding that if we are going to live here permanently, how would we design a city to go about doing that?"

Roanoke has had 18 floods in 125 years--one every seven years--causing more than $200 million in damage. Cain's organization, whose hazard mitigation team has worked with AMERICAN FORESTS' urban forestry department, is implementing an environmental approach working from the traditional disaster-management point of view.

"We are trying to change the culture and the way it preserves our water quality," Cain says. "We either have floods or drought. The other potential for damage here is wildfire and each of those is water-quality related. By using a low-impact approach, which we are trying to teach foresters, farmers, builders, and developers, we are hoping to not just restore the hydrology of the watershed, but to also clean the water at the same time."

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Because trees slow stormwater runoff, allowing water to soak into the ground rather than run off into streams or storm sewers, trees are an important natural tool for areas prone to flooding. In a rural area the runoff rate might be only 10 percent; in a more urban, downtown situation that percentage can easily soar to 55 or 60 percent or greater.

Dan Henry, Roanoke's urban forester, worked with AMERICAN FORESTS on an Urban Ecosystem Analysis, conducted in 1998, that showed tree cover slipping from 40 percent in 1973 to 35 percent in 1997. A second, more detailed analysis in 2002 used high-resolution imagery to evaluate the city's current 32 percent canopy. As part of that analysis AMERICAN FORESTS also created a digital "green data layer" for the city to use with its Geographic Information Systems (GIS) data. These data and tools will help city officials plan future development while keeping nature in mind by calculating the dollar value of the "ecosystem services"--stormwater control and air and water quality--its trees provide.

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FROM ANALYSIS TO ACTION

After the presentation of the UEA, Roanoke's city council and planning commission formed a volunteer, citizen-based urban forestry task force. Its goal: to develop a basic urban forestry plan that addressed canopy loss. The group's comprehensive urban forestry plan was approved by the planning commission and adopted by the city council in April 2003.

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That action made Roanoke the first community to adopt a tree canopy goal--40 percent citywide within 10 years--as a result of Urban Ecosystem Analysis findings. Another goal is to plant enough trees on public ground to reverse the current annual net loss.

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The UEA's findings have prompted other changes as well: revisions in public policy, a new urban forester position, and support for greenways and low-impact development. As the city moves toward its 10-year goal, it has increased its urban forestry budget by $50,000 to help pay for the additional tree planting. The city also received a grant from the Virginia Department of Forestry to help fund a part-time urban forestry planner to shepherd the task force and help implement the plan, Henry says.

The first priority in implementing these changes is to slow the decline of publicly owned trees by planting at least as many trees as the city removes each year, Henry says. "For publicly owned tree stock, our goal was to increase that by 25 percent, which would be the same proportion we are looking at overall to increase from 32 percent to 40 percent."

The trees are planted on city-owned land such as parks, residential thoroughfares, libraries, municipal complexes, public works facilities, and recreation centers. The city is also undertaking a commemorative tree program.

"While there are no incremental benchmark goals, we did call for trying to obtain funding to have AMERICAN FORESTS do an analysis with updated data at the five-year mark to see if any progress had been made," he adds.

While tree planting may be a very visual sign of the city's efforts, it's actually a small component of the overall strategy, Henry says.

"It's an easy one to point out, but the more effective ones are changes we are currently making to our zoning ordinances for landscape regulations for developers. In our draft zoning plan, we've called for the planting of trees in the interior and the perimeter of parking lots, with parking lots being seen as one of the most obvious places gains can be made through reducing impervious surfaces."

Having this plan in place helps not only get these types of regulations into the draft zoning plan, but will help defend those regulations as they go through the review process, he adds.

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"We see a lot of value in the reports and in the plans that follow to help, because there is so much pressure by homebuilders and developers to take a lot of these provisions out of ordinances. It all helps to educate them on the need for those types of green infrastructure elements to be incorporated into their developments."

Although a lot of the solutions focus on the bigger picture, focusing in on specific areas has been helpful. Natural resource managers tend to think in terms of regional or broader efforts, Henry says, but it was helpful to have GIS information that allowed the city to analyze the data by political or ecosystem boundaries.

"When you deal with governments, you've got to focus back on those boundaries when you start talking dollars and cents and impacts to those communities. While they may claim some concern with the valley at large, they're really only going to act if they can be shown their government location is affected in a monetary sense." In other words, there may be regional concern, but local decisions are made locally.

"We used those [UEA] studies to their maximum advantage," Henry says. The more recent study gave some numbers specific to localities, helpful in places having trouble getting a tree ordinance passed. "We presented the plan's findings to the town board and got them to approve their tree ordinance, which they never had before," says Henry.

In Roanoke, the study showed the existing canopy had a stormwater retention capacity of more than 64 million cubic feet. If Roanoke were to lose all its trees, this one particular service would be valued at $128 million.

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"We were using the first satellite survey to talk to all kinds of people across the state," remembers Charles Blankenship, a retired forester and citizen activist. "Several of us in the Valley became members of the state's Urban and Community Forestry Council, but also during that period of time we came to the conclusion that greenways were essential to lace together the residual larger blocks of urban forest that we had."

"It all comes back to the UEA," Blankenship says. The Urban Ecosystem Analysis brought tree loss into focus and put the importance of the urban forest into the city's planning process.

This generated additional funding for urban forestry and caused ripples that spread throughout the region, ranging from support for Roanoke Valley greenways to individual neighborhood development and infrastructure retrofits using low-impact practices for handling stormwater. The study also spurred citizens to take an active role in shaping their community.

The Roanoke Valley Urban Forestry Council, started by Blankenship and a small group of volunteers in the early 1990s, is focusing its efforts on creating greenways in the Roanoke Valley. Elizabeth Belcher, coordinator for Roanoke Valley Greenways, is coordinating the fundraising effort.

"We've got a great conceptual greenway plan that was adopted by the community and we're nibbling away at that," Blankenship says. "Our principle interest is trying to get that Roanoke River greenway completed, and then we will spur off to neighborhoods and adjacent communities."

As with all the plans underway for Roanoke, a key concern is to lower the potential for flooding, and Blankenship and his peers have been working with Project Impact's Cain to incorporate that thinking into their plans.

Roanoke, with a population of 94,911, is a low-density city, and "there is a lot of land here being routinely mowed by people without thinking about it, where maybe it would be better just to put back trees," Cain says. "Sixty-five percent of the area around here ... is still forested. Some 20 percent is still farmed." Since much of the area remains undeveloped, retrofitting is a viable option, he says.

"It costs a little money," Cain concedes, "but as parking lots are repaved, they can be repaved so that they flow into swales and are greened in such a way that the plants filter out the pollution coming off of the runoff. It's taking a long-term view. With new developments you can do this instantly, but in existing developments you can go back and refit. One hundred years from now, we will probably have gotten our jobs done."

Given Roanoke's location in the watershed, Cain says, "the main point about implementing solutions here is that you help people for hundreds of miles who don't even know that they were helped."

RELATED ARTICLE: DOCUMENTING ROANOKE'S GREEN

Though the Urban Ecosystem Analysis studies provided valuable information that focused the Roanoke area on its dwindling tree canopy cover and the associated environmental benefits, the real value of the project lies in the "green data layer" produced to guide future planning.

This digital GIS map identifies tree cover, grass, open space, impervious surfaces, and other land-cover types. When used in conjunction with CITYgreen software, the data will calculate the ecological and economic benefits of tree canopy for slowing stormwater and improving air and water quality. By modeling future development scenarios with this data, community leaders can make better decisions about controlling flooding as well as development.

New high-resolution satellite imagery can identify individual trees with a 6-foot canopy spread, making it an ideal scale for GIS planning. Raw imagery, shown as a true-color satellite image (below, at right), is captured by a satellite during the tree's active growing season. GIS analysts then classify detailed characteristics of the imagery into different land-cover types.

The classified green data layer (shown at left) assigns different colors to each type of land cover. Dark green represents tree cover, light green represents grass and open space, and gray designates an impervious surface. Each community within the study area can incorporate this data layer into its GIS to use in urban planning.

Using the green data layer from the 2002 study with CITYgreen software, the UEA revealed that the greater Roanoke area's urban forest removes 5.9 million pounds of pollutants annually, at a value of $14.6 million to the communities. The trees in these 10 communities have a stormwater retention capacity of 313 million cubic feet, saving $626 million in potential runoff costs. The city of Roanoke currently saves $128 million thanks to the retention capacity of its urban forest, which is able to hold 64 million cubic feet of runoff. Trees within the city of Roanoke also capture 948,000 pounds of pollutants annually, a value of $2.3 million to the city and its residents.

The green data layer can be analyzed in ways that are useful to city leaders, planners, engineers, and environmentalists either by political boundary, such as a city, neighborhood, and land use, or by ecological boundary, such as a subwatershed. Planners can also model different development scenarios that affect tree canopy to show the changes in environmental benefits that would result, thereby making better planning decisions.

--Cheryl Kollin

Carol Brzozowski writes from Coral Springs, Florida.