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  What We Do

Stream Crossings: Trails… from a River’s Point of View

“I hear footsteps….”

There’s more to me than you might know...

  • I am a river. Illustration shows a fish swimming in a rocky stream.
  • I am dynamic, ever-changing.
  • I am pleasing to the eye and to the ear.
  • I cut through the earth.
  • I meander across the landscape.
  • I carry water, sediment, and debris.
  • I adjust my shape to maintain balance among runoff, sediment, and slope.
  • I provide critical habitat for unique and diverse communities of aquatic and terrestrial organisms.
  • I am home to many species of fish, mollusks, insects, amphibians, mammals, reptiles, and birds.
  • I provide transport routes to their areas of food, shelter, reproduction, and colonization.
  • I change and evolve over time in predictable patterns.
  • I tend toward stability unless disturbed.

Image shows a woman standing in a deeply eroded trench. Photo courtesy Mike Furniss, US Forest Service.    Trails can harm me, or be my welcome companions;
poorly designed, constructed, or maintained trail crossings can:
  • Deliver polluted runoff and sediment to my channel.
  • Divert, capture, or block my flow.
  • Cause my channel to become unstable and disrupt transport of water, sediment, and debris.
  • Impede or bar passage of fish, macroinvertebrates, and other aquatic organisms.
  • Fragment habitat by creating impassable water depths, flow velocities, or jump heights.
  • Impair or prevent access to food resources, refuge from unfavorable conditions, reproductive success, and new areas for colonization.
  • Diminish biological diversity and species abundance.

I prefer solitude Image shows a bridge crossing high over a river. Photo courtesy Gary Weiner.

  • It’s best to keep your distance – avoid interacting with me; trails can be too close for comfort.
  • Travel parallel to my course, rather than perpendicular to it.
  • Select a path that’s higher, flatter, and drier.
  • Leave a healthy fringe of vegetation -- riparian buffer -- between me and a trail.

But, if you must come near or cross me…

  • Minimize the number of crossings. Image shows a bridge crossing over a stream. Photo courtesy Gary Weiner.
  • Cross where my channel is most stable – at a riffle or where my banks are solid rock.
  • Use a bridge instead of a ford or culvert.
  • Span as much of my active floodplain as possible, preferably at least twice my bankfull width.
  • Use an armored ford instead of a culvert.
  • If you must use a ford or culvert – minimize the width of the ford or length of the culvert.
  • Mimic nature – don’t change width, depth, or gradient.
  • Image shows an armored ford across a river. Photo courtesy Mike Furniss, US Forest Service.
    • For culverts, use a natural bottom – don’t change the substrate.
    • For fords, armor the crossing if the natural substrate consists of clay, silt, sand, or gravel. Use stones large enough to withstand scour during flood events.
  • Size culverts to handle the largest expected flows and to allow a flood fringe to develop inside.
  • Design the approach, to descend into and climb out of the crossing, at an 8% grade maximum.
  • Provide grade reversals on both approaches to prevent water and sediment from entering the stream.
  • Get runoff from the trail into the soil – use outslopes, dips, and waterbars. Avoid outside berms.
  • Plan and design for possible failure of the crossing.
  • Integrate other restoration activities into the design and construction of new or rebuilt crossings.

If you can do all this, we can peacefully coexist, but, there will be times when I will flood’s natural!

Click to learn more about stream crossings.

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