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    1. Erosion Control
    2. Vegetation Management

    Sustaining Greenspaces in Urban Places: BMPs for Municipal Natural Areas

    March 1, 2002
    For many of us who live in cities, it can be a delight to drive to a nearby natural area, pull onto the shoulder, let out the dog, and cut uphill to join him on a trail that leads to solace, beauty, and refreshment. For others, urban greenspaces offer challenging terrain for close-to-home workouts or thrilling mountain-bike rides. There is no doubt that natural-area parks make important contributions to the quality of life in places that are becoming more populous. Yet as such places get used harder, greenspace managers need new assessment tools to help them gauge the impacts of increasing park uses on water quality and natural resources. Even more, they need proven practices that can help them rehabilitate natural areas or avoid natural-area degradation and also preserve wildland parks in urban settings.When natural areas begin to show signs of overuse, chances are that nonpoint erosion is increasing. Road shoulders become denuded and rutted from casual parking. Trails in wet areas gradually get wider where more and more hikers and bikers make their way around the muck. New downslope trails and scramble routes appear where people create paths to streams, scenic overlooks, or other places they desire to go; these trails then begin to erode. Impromptu, leash-free areas first become trodden, then get raw under the prancing of myriad happy dogs as years pass. Even maintenance activities and the maneuvering of maintenance vehicles can contribute to denudation and nonpoint erosion.For the most part, these changes are so gradual that people tend not to recognize them. Over time, park managers and workers come and go, people who use the park move away and are replaced by others, and even the governmental entity responsible for the park might change. Although old-timers might describe the park of their youth as a wilder place, such stories might be regarded by others as a child’s perspective skewed by the lens of memory.But as time passes and the park gets more and more threadbare, an unseasonable storm can serve as a wake-up call for a different management view. A convective thundershower in July can lash out and transform a steep trail into a supercharged ditch that drains directly to a wetland, a casual parking area can become a hazardous quagmire, or a leash-free area can turn into muddy mess whose runoff swills out of the park and into municipal storm inlets. During a flashy runoff event, an entire streambank can give way where park planners might have allowed vegetation to be removed for a streamside trail. Today, as municipalities reorganize themselves in order to meet the requirements of National Pollutant Discharge Elimination System Phase II and the standards for total maximum daily load (TMDL) streams, the impacts of such weather events are no longer being looked upon as acts of nature but as the responsibilities of local government. Park administrators are becoming partners in the achievement of watershed goals. They are assessing conditions; retrofitting facilities such as trails, roads and road drainage, parking lots, and high-use areas; and applying planning and design best management practices (BMPs) to passive recreation facilities that will be installed in the future.This is a major shift in the role of parks in urban settings, and it requires that both decision-makers and the people who carry out park policies on the ground possess the appropriate training and education to apply good judgment to facility planning and day-to-day park maintenance activities.BMP 1: Education

    Runoff sediment from high-use areas can flow to public stormwater systems, putting urban greenspace managers in the limelight as vital players in local water-quality plans.As park managers who have faced deepening cuts in maintenance budgets know, keeping maintenance crews adequately trained can be a monumental challenge, particularly as personnel come and go. And as park administrators know, there is a world of difference in the level of training that park facility designers bring to projects that might have complex environmental consequences. For these reasons, it is essential that a set of administrative BMPs be put firmly in place to support the planning and maintenance activities that sustain the environmental quality of natural-area parks. The first of these is education. BMP 2: FundingThe second essential administrative BMP is funding. Without it, staffs might never get trained, deteriorating facilities might not get upgraded, and new facilities might ot be properly designed. Increasingly, municipalities are getting wise to this. Where they are under the gun to meet water-quality and endangered-species requirements, many cities are couching the costs of their park maintenance and staff education activities in their compliance plans for TMDL streams. Where voter-approved bonds will be needed to pay for lands to be acquired and managed as urban greenspaces in the future, experience has shown that the public is willing to pay when parks engage it in programs, planning, and problem-solving.BMP 3: AssessmentAs nonpoint erosion increases, managers face decisions about relocating activities and realigning trails.The third essential administrative BMP is assessment, which is critical to prioritizing and guiding park projects. For example, a nonpoint erosion assessment can help determine whether runoff from unsurfaced roads, trails, or other high-use areas creates detrimental impacts. Planners might start by determining the fate of park runoff both within and outside park boundaries. Subwatersheds of the natural area that drain to TMDL streams, wetlands, lakes and other water bodies, and related sensitive areas will be delineated. Subwatersheds that drain to public rights of way and storm inlets will be identified. Finally, the potential public health and safety impacts of erosion, mass wastage, or drainage problems stemming from park use or facilities will be identified.The findings of this watershed-scale analysis can be used to prioritize projects. For example, a trail or a road where runoff and erosion affect a lake, a stream, or a sensitive resource such as a wetland would get on the high-priority list for retrofitting.BMP 4: ProgrammingIn the context of park use, programming most commonly refers to the classes and events hosted in the park. As used by architects and landscape architects, however, programming refers to the way people use space, as influenced by lines of sight; the placement, height, and design of objects; and other subtle influences such as light, space, color contrast, and even sound. Park planners and maintenance people can use these principles to direct uses away from some areas and toward others. For example, at a very basic level of park programming, native shrubs might be installed on roadside verges where parking is discouraged. This choice might alleviate the need to post prohibitive signs, which park visitors often find offensive–particularly if many activities are prohibited in the park. Another drawback of signs is that they require maintenance around their bases, such as weed whacking or application of pesticides–both of which are labor- and cost-intensive and can contribute to other problems. Subtler programming might be the placement of a large rock or root wad close to the edge of a trail where people or bicycles tend to wander outside the tread. Highway managers have used such visual “pinch points” for years to affect the rate of speed on rural highways. The same principle can be applied to trails.BMP 5: Vehicle ControlsMany greenspace managers are assessing water-quality impacts of trails at the water’s edge.Traffic controls and signage (or lack thereof) can have profound influences on the use of natural areas. For example, a right-turn-only sign can route cars away from a trailhead at a heavily used or sensitive area and toward an area in which a new trail or other amenity has been made available. Parking or entry fees can be used to limit the number of visitors. Some natural areas can be closed to vehicles on certain days of the week.BMP 6: Public OutreachLimiting the kind of use in a natural-area park is a touchy matter. People tend to get bad feelings about a park and the government associated with it if they sense that park uses are being controlled by means of tickets and citations. Yet the impacts of some uses might be greater than can reasonably be sustained by area trails and natural resources. Many park and wilderness-area managers like to use a collaborative assessment and planning model, The Limits of Acceptable Change (1985), to judge the social and natural resource impacts of visitor use and to consider alternatives. The nine-step public process starts by identifying social and resource issues and concerns. Indicators of these concerns are selected, and inventories of both social and resource conditions are completed. Often, community members help complete the inventory. Based on inventory findings, standards for park condition are set. Alternatives are identified and weighed against these standards, together with potential management actions. Each alternative is evaluated, and one is selected.Where trails cross low or wet areas, widening is certain to occur, causing undesirable sedimentation impacts on aquatic and wetland ecosystems. Diverse structural solutions are available.When this process is carried out with the involvement of people who use the park, several things begin to happen. Park management is less likely to be perceived as the “bad guy,” and the various user groups have an opportunity to participate in framing the problem and developing solutions. Members of these groups then influence their peers. When collaborative communication occurs between users and managers, parks develop enduring relations with all their user groups. In this way, outreach education becomes possible and a culture of park stewardship begins to develop. At this point, a continuing culture of stewardship can be furthered by the programs offered in the park, such as wildlife tracking, bird walks, and trail work parties.BMP 7: Special-Use AreasRegional centers for specialized uses such as all-terrain vehicle riding and off-trail mountain biking often become designated and established as an outcome of local planning processes that involve the public. Successful establishment of such centers relies, in part, on a healthy communication network in which all park managers in a region regularly share information with all user groups and their member associations. This network is essential to achieving success in managing human impacts on natural-area parks.BMP 8: Interdisciplinary PlanningAlthough designers typically develop park master plans, it is essential that physical, biological, and social scientists provide input. Consider, for example, the unintended consequences that can result from trail hardening. Many managers of natural-area parks eventually must make decisions to harden trails as a result of increased uses. But ironically, trails that have been widened and surfaced are likely to attract even more users than before. When this happens, interpretive signage in the park might need to be added to attract certain users and to elicit “soft” behaviors. Park entry information might need to be upgraded and differently disseminated. School outdoor science programs might be invited to carry out studies in such parks in order to nurture a culture of stewardship in the next generation’s park users. There are many social considerations that go along with a decision to harden a trail.While hardened trails do away with some problems, they invariably create others. A narrow, unsurfaced “fisherman” trail along a riverbank might be inundated occasionally by floodwaters and emerge relatively unaffected. But if such a trail is widened to 3 or 4 ft. and surfaced with compacted gravel or pavement, it can magnify the erosion impacts of overbank flows. This is because the hardened, smooth surface will have the capacity to accelerate flows and, therefore, to increase their erosive potential. Recall that as velocity doubles, the ability of a flow to transport mass is squared. The former, narrow trail was flanked by vegetation, which decreased the velocity of the overbank flows. But in its new state, the riverbank trail in the floodplain becomes an agent of erosion during flood flows. Park managers have to see this nightmare only once to conclude that the decision to harden a trail requires careful analysis of alignment and location by fluvial and riparian specialists. In another example, maintenance staff might decide to construct an earth-filled crib to elevate a trail over wet, soft ground. In a few years, however, the crib could fail from a lack of subgrade preparation, inappropriate fill material, and no mechanism for internal drainage. In other settings, hardened trails might create concentrated drainage that can undermine the trail at the drainage discharge point or create a direct flow route that delivers both water and sediments to a nearby stream or wetland. Such problems are commonplace in the absence of properly prepared park and trail master plans and/or in park settings where the maintenance staff makes decisions about trail upgrades without the guidance of clear standards. Engineering, drainage, and erosion standards need to be carefully incorporated into master plans, standards, and on-the-ground BMPs.BMP 9: Set Goals and ObjectivesInterdisciplinary master planning for natural-area parks can help shape decisions about facility location and reduce the need for spot fixes.Natural-area parks are always in an education mode and their programs can be powerful ways to influence the behaviors of park users.Park and trail master plans need goals and objectives for which specific on-the-ground BMPs can be fine-tuned. A typical trail master plan starts with a set of goals, such as the following: 1. Develop a four-season system.2. Serve multiple user groups and ability levels.3. Preserve scenic resources.4. Protect threatened and endangered plants and wildlife habitats.5. Protect water quality, wetlands, floodplains, and streams.6. Preserve historic resources.7. Control erosion and protect exposed soils.For each goal, it is important to flesh out a set of supporting objectives. For example, objectives for Goal 5 are shown in the sidebar. (click here to read sidebar)BMP 10: On-the-Ground PracticesThe very final element of the trail master plan is the specification of BMPs to meet each of the plan’s objectives. In addition, BMPs need to be assembled to guide seasonal, annual, and periodic maintenance activities. The plan should contain BMPs to address typical problems that develop on trails at the edges of streams, in wet meadows, at contacts of geologic layers, at the toes of slopes, and along trails that fall with slopes. It should contain a strategy for using BMPs to retrofit, decommission, or relocate trail segments and high-use areas that are chronic problems.BMPs should be built into the plan to address all other park operations that will affect trails. For example, a common problem in parks with wide or surfaced trails is that park maintenance vehicles begin to drive on them to cut down on the time and/or labor involved in reaching distant areas to perform routine maintenance tasks. This often results in degradation of the trail surface or subgrade. Along the same lines, informal cross-country routes traversed by maintenance vehicles commonly become trails. When improperly located, these routes often develop chronic drainage and erosion problems. For these reasons, the maneuvering of operations and maintenance vehicles should also be part of the master plan.It is easy to see that implementing on-the-ground BMPs should be the final action step for preserving wildland parks in urban settings. Too often, physical BMPs are applied first, absent of carefully crafted goals and objectives for natural-area parks. In organizations where capital projects drive funding, such planning often is left unfunded. For this reason, community involvement, outreach, and education are essential to the long-term health of urban greenspaces and their watersheds. They create and sustain voter support for natural-area planning and for the ongoing education of park users, planners, managers, and maintenance workers in an organization that is always in an education mode and whose education customer is always new.