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The Ivy Creek Greenway is surfaced with boardwalk in some sections to protect wetlands and floodplains. 



Sustainability – The capacity to endure. Specifically in reference to development, sustainability means building and planning with future resources (ecological, economic, cultural and political) in mind.

Locally rare species – A species that may be abundant overall, but is contained to a specific, rare habitat.

Globally rare species – A species that has an overall low population throughout the world.

Invasive species - A species nonnative to a habitat that has shown a negative impact since introduction.

Succession – The process of change in an ecological community over time, marked by stages of plant and animal life that pioneers and then matures an area until it becomes stable.

Microclimate – A local atmosphere zone where the temperature, wind, atmospheric pressure and other weather-related factors may differ from the surrounding area. A shift in climate from one area to the next may mean a drastic difference between their ecologies.

Trails Glossary and Acronyms


RTC Resources

Ask Our Listserv: Learn about trail development from the experts! Join our listserv to be connected to more than 900 trail managers, advocates and builders across the country.

Go to RTC's Trails and Greenways Publication Library

For more information, please contact the appropriate regional or national office.


Additional Resources

Endangered Species Act

About Environmentally Sensitive Areas

Dealing with Environmentally Sensitive Areas: The best practices, according to British Columbia's Ministry of Water, Land and Air Protection, Ecosystem Standards and Planning,
Biodiversity Branch.

NOAA Environmental Sensitivity Index

National Fish and Wildlife Service's listing: For information about environmental issues and sensitive areas by state.

Constructing Wetlands Boardwalks and Trails: A guide by the Association of State Wetlands Managers

More about the Edge Effect

Rails-to-Trails Conservancy's Executive Summary of Floodplains: A compilation of frequently asked questions from Rails-to-Trails Conservancy's listserv, documenting reliable answers to questions about trail development in floodplains.

More about permeable trail surfaces


Plan, Design, Build

Developing Trails in Sensitive Areas

Explore the latest resources on this topic:

 Environment in RTC TrailBlog
 Environment in the Library

Building a trail in a wetland, wildlife reserve or beside farmland can provide fascinating trail features and an overall unique experience. However, these places can also be ecologically or otherwise vulnerable, and construction in them can have potentially negative repercussions. With thorough research and careful design, it is possible to develop a trail in or near sensitive areas and habitats.

Keep in mind that constructing trails in these areas means adhering to a variety of local, state and federal laws and regulations, as well as basic, universal principles of environmental stewardship.

Environmentally Sensitive Areas

An environmentally sensitive area is a place wherein plant or animal life or their habitats are especially valuable or rare (locally or globally) and can be easily disturbed or degraded by human development. The protection of these places is mainly an effort to preserve endangered or threatened species, but it is used to defend productive ecosystems or limited resources as well. Some examples of particularly delicate habitats are:

  • Wetlands
  • Estuaries
  • Seaside regions
  • Designated wildlife areas
  • Grasslands
  • Cliffside regions
  • Mountainside or mountaintop regions
  • Certain forests (including riparian)

Any ecosystem can be a sensitive area—the classification as such depends on the needs of the native species. These zones might limit construction legally, and in some severe cases, trail projects may need to be moved or canceled for the sake of biodiversity or resource management. This is especially true if the trail is expected to see heavy use. Consult an ecologist if a sensitive area is hosting trail development. Studies and surveys can be made to determine the level of sensitivity and potential trail impacts. Natural heritage programs, nature centers, local naturalists, birdwatchers and even hunters can all be valuable trail design resources. Know the species that need the most protection and try to accommodate their needs in trail design.

What to Consider

Each area will present its own challenges when pursuing sustainable trail building depending on the species, resource or habitat at risk. These challenges can be analyzed with environmental assessment, which should always be conducted before trail work begins. Assess the animal life, as well as the soil, geology, vegetation, water and climate in the area. Before the Great Western Trail was built in Polk County, Iowa, an extensive survey of the trees and an archaeological search were conducted. Understanding the complexities of a corridor's environment is essential to creating a successful, safe and sustainable trail.

Area of Development
The most important factor to consider while planning such a project is creating a buffer zone between the trail and essential parts of the vulnerable area, like nesting places. This will mitigate any direct effects from trail usage. Limit access, activities and facilities in areas near or in these extra-sensitive locations.

Another particularly important place in any habitat is the "edge." An edge is where one interior zone (divided by soil type, use, types of landforms, etc.) abuts another; for example, where a floodplain ends and deciduous forest begins, or where the forest ends and an area of human development begins. Edges are important dynamic places of transition, and because of this, many species may reside there. A trail should not be built in an edge zone. A one-to-one ratio of trail distance from an edge to the width of the edge itself is recommended. If there are unique or interesting trail elements within an edge zone, site the trail away from it, but add lookouts or scenic overlooks.
In general, trail construction should be as contained as possible as to not frighten or disturb wildlife. Some species of birds will abandon their nests if their habitat appears threatened. Tools should be kept small and simple whenever possible to prevent excess noise or damage to habitats. Design must also avoid fragmentation of habitat, as some species may suffer from interbreeding, roadside death, competition with other species or starvation without adequate range.

Put barriers in place to protect underbrush and to discourage trail users from wandering. Existing vegetation, which should be preserved, can be used as a natural barrier. When planting, consider the microclimates different trees produce. For instance, deciduous trees, such as oaks, provide shade, while evergreens protect against wind. Always follow up-to-date tree protection and planting standards, and try not to disturb existing tree roots.

Do not be fooled by open landscapes like marshes and grasslands: their vegetation, though low, is extremely important to their health. These delicate environments lack canopy, so they are continuously exposed to sunlight and other elements. Their plant life is specifically adapted to withstand the impact of wind, heavy rain and severe temperature changes.

Avoid using mowed turf along a trail, as it is often costly and difficult to maintain, and never introduce non-native species of plants to a trail. Non-native, invasive or noxious species can poison wildlife, choke out native species or otherwise be detrimental to a trail's environment. Invasive species are difficult to get rid of and are not properly adapted to an ecosystem they don't belong in. Because of this, they may not hold soil as strongly as native species, meaning their presence can increase erosion. Moreover, native plants will grow more easily than exotic ones, and need less, if any, pesticides or fertilizers.

If there are invasive species or weeds located along a corridor, the use of synthetic weed killers is a last resort. Some noxious plants have specific methods of removal, but the basics of managing invasive species can be found here. As for removing weeds, there are many alternatives to herbicides, including pulling, mowing, and, in the case of Idaho's Weiser River Trail, goats!

The soil in a sensitive area is a vital resource, as it supports natural processes, prevents flooding, filters water and affects the environment's overall ecology. If soil must be moved, hand tools or small power tools can be used. In the case of a seaside or estuary-side trail, this may be necessary in order to move the sand.

When deciding on a trail surface, porous surfaces (mulch, porous asphalt or organic surfaces) are a high priority. They allow for water drainage, which prevents flooding and nourishes the plant life. Wetlands and other floodplains can especially benefit from the use of boardwalks as a trail surface. Though slippery when wet, boardwalks allow for drainage as well as plant growth and decomposition beneath them. In addition, they make interesting trail features, such as the beautiful boardwalk at the Ivy Creek Greenway.

Use soil content data to inform your decisions: fine grain sand and heavy clay will not drain quickly, while coarse grain sand will. Through survey and assessment, soil content and essential environmental landmarks, like aquifer recharge zones, may be discovered. Surfaces over these zones must be kept permeable to ensure clean water supplies locally. Avert erosion and flooding further by stabilizing banks with vegetation and designing trails to follow the existing grade. Floods and erosion not only degrade the landscape upstream, but also pollute the watershed downstream.

Many environmentally sensitive areas are in or around a water feature of some kind. Wetlands, marshes, swamps, rivers and estuaries are some of the most vulnerable places in the United States. Because of their own internal productivity as ecosystems and their influence on overall watersheds, drainage corridors and their wetlands play an extremely important role in supporting the earth's flora and fauna. All bodies of water are part of a larger interconnected web—an action at one pond can potentially influence a coastal zone greatly. Considering this information, when developing in these places, all decisions must be made with water quality as a major concern.

Rivers carry nutrients from snowmelts on mountaintops through lakes, ponds, wetlands, bays and then to the coast. Any upstream development is bound to have downstream effects. Use tactics to prevent erosion and flooding, and avoid the use of pesticides and fertilizers, which can create harmful algal blooms or dead zones in water. When installing boardwalk railings or signposts in water, try not to use wood, which may be treated with toxic chemicals. Instead, consider recycled plastic or concrete posts as options. Encourage upstream landowners to follow sound conservation practices: their pollution is ultimately the trail's problem. Additionally, do not remove riparian vegetation, which naturally holds soil and filters water of many pollutants.

Natural Processes
In order for a corridor and its wildlife to stay healthy, the natural processes of the habitat need to remain uninterrupted. Forest floor cover should be left alone to undergo decomposition, which is important to soil quality. Depending on the location and survey-determined sensitivity of the corridor, major changes in climate may or may not be a concern. Changes in vegetation or the flow of air or water should not have much of an effect unless the corridor is already contained within a microclimate. Speaking with a qualified climatologist about the corridor will clarify the severity of this issue. Mountaintop, mountainside or cliff-side regions, which often have different weather from surrounding locations, may need more attention than a forest.

However, some forests, grasslands and other environments must be allowed their process of stress, disturbance and succession instead. The "stress," usually in the form of fire or flooding, may destroy an environment somewhat, but will ultimately renew it through succession. In the fire-sensitive New Jersey Pine Barrens, the Barnegat Branch Trail has been built away from heavily-wooded zones to avoid the impact of prescribed burns. These controlled burnings are necessary to revitalize the soil, prevent the growth of invasive species and fuel the growth of the native pitch pine. The trail's managers still plan for fire-related hazards with signage and appropriate trail-closing procedures.

If a corridor is located in an area prone to frequent fire or flooding, know where and when these events typically take place, and relocate or close a trail appropriately. When paving trails or building facilities, choose surfaces that are fireproof or otherwise sturdy so they do not have to be replaced frequently. Signage should be installed to both educate and warn trail users about the cycles.

Dark Skies
For some animals, especially nocturnal ones, unnatural light may interrupt sleeping, hunting or mating habits. Trails built in sensitive areas can avoid causing light pollution with direct, low lighting or no lighting at all. To learn more about Dark Sky-regulated lighting, see our Toolbox page on trail lighting. Depending on the wildlife, trail night use and construction should be limited for the safety of both the species and trail users.
Even with thorough planning and sustainable trail practices, increased human activity may still drive off some species. Always consider the potential ecological repercussions when developing a trail.

Other Sensitive Areas

A floodplain is land adjacent to a stream or river that stretches from the banks of its channel to the base of the enclosing valley. As the name suggests, floodplains are often subject to flooding during periods of high discharge. Their proximity to water features makes them fascinating locations for trails, but delicate ones too. Gradually or suddenly, a section of trail may be wiped out, leading to high maintenance and repair costs that are likely to recur. Conduct a thorough investigation of corridor conditions and drainage before building. Using this information, a trail may be designed to lower the risk of flooding altogether by providing a place for water to flow. After observing water stewardship practices (see above), there are a few more things that can be done to make a trail more able to withstand water.

In an area with consistent major flooding, a permeable trail surface will not help much. Concrete is the best surface for withstanding flood conditions, especially with transverse saw cuts in it to relieve pressure. Unfortunately, the advantage comes at a high price: concrete paths are the most expensive trail surface to install and repair. Asphalt is a cheaper, smoother option, but may need repair more frequently and holds heat in the summer. Constructing an asphalt path with a deep base and a turn down below finished grade may improve its durability. If the flow of floodwater intersects the path, rocks along the trail can cut water volume significantly. Waterproofing products and specialized paints can help mitigate damage as well.

There are many successful trails, like the Toonerville Trail in Vermont and the Indian Bend Wash Trail in Arizona, that see frequent flooding. Dealing with these floods is all about understanding the area and planning around issues. Still, no trail in a floodplain will withstand all flood conditions, so have strategies and facilities in place to deal with trail closure and repair.

Farms and Ranches
Farmland and ranches are sensitive in terms of vegetation, privacy and the division of public and private property. Open communication with surrounding property owners is vital. Listen and be honest, and take into account how the trail may affect their livelihood and land. Make sure to coordinate construction times and locations with landowners as to preserve privacy and not distress animals.

Wherever possible, use public land and do not fragment farms. Build the trail away from barns, crops or anything else that can be looted or vandalized. Where a trail runs close to private property, clearly delineate the trail and utilize buffers like space, low-maintenance vegetation, water features, terrain elevation or dikes. Gates and fences can be used when necessary. During and after construction, surface water drainage must be managed appropriately. To avoid disrupting any current irrigation, a permeable trail surface should be considered. Warn trail users about farm equipment with clear signage. Such signage could also encourage respect and understanding of farm practices, property and communities.

A brownfield is land that is or may be contaminated by a hazardous substance or pollutant. Trail development in these places requires much surveying and clean up, but can still produce a meaningful trail. For more information about building a trail in brownfields, see our Toolbox page on environmental contaminants.

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