Sustainable Trails: Bridges & Boardwalks
The Land Trust is committed to providing a safe and enjoyable experience for trail users while also protecting our natural areas. Occasionally, that means constructing bridges and boardwalks along our trails. Have you ever wondered what’s behind the decision to build a bridge or a boardwalk? We’re happy to share.
Streams, creek crossings, and natural terrain features are the most common motivators for bridge installation. Most of the streams and creeks in our area have rain-dependent water flows, meaning they are typically dry except during seasonal rains or as runoff drains away. Where trails cross these wash areas, there’s potential for problems. Trail traffic in the streambed can stir up sediment, displace rocks and soil, and increase erosion. The irregular, slippery surface of streambeds and the presence of high or fast-moving water can also be a potential danger for trail users. Simply elevating the tread path over the stream or creek with a bridge can protect the streambed (along with the plants and animals that live there) and provide a safer experience for users.
Boardwalks are essentially a series of bridges and offer many of the same benefits, elevating the tread path above low areas, poorly draining areas, seasonal wet zones, and sensitive habitats. Trail layout is often restricted by terrain, topography, and property boundaries, which makes it difficult to avoid these types of trail challenges in all cases. When appropriate, a boardwalk can limit erosion due to usage (continued traffic on muddy trails can damage the trail bed), enhance the user experience (no one likes slogging through the mud), and protect spaces and species from constant disruption (especially from hikers going off trail to bypass muddy areas or displacing rocks, etc. while crossing creek beds).
Bridges and boardwalks offer many benefits but they do come at a cost. The materials to construct them can be expensive. They require time for construction, inspection, and maintenance to ensure they remain functional and safe. Actual construction can be difficult in isolated areas far from trailhead access and, although we work hard to minimize the environmental impact, there can be temporary disturbances during construction. However, in many cases the long-term benefit to the surrounding the environment due to rerouting foot traffic can justify the temporary disruption. The introduction of manmade materials in the natural setting is also a concern for some. For all of these reasons, the Land Trust uses bridges and boardwalks sparingly, but when the conditions dictate the need for improved safety or protection of the land, the benefits can certainly outweigh the costs.
This post is part of a series highlighting Land Trust of North Alabama’s commitment to sustainable trail building in an effort to ensure the long-term sustainability of our trails. Funding provided through a Restoration and Resilience Grant from the National Environmental Education Foundation (NEEF), with major funding support from Toyota Motor North America supports current trail restoration projects on Monte Sano Nature Preserve and public education about the importance of responsible construction, maintenance, and trail use.