Managing Environmental Impacts of Erosion and Sedimentation of and from Low-Volume Roads

Focus Area

Water Quality/Wetlands

Subcommittee

Natural Resources

Status

Archived

Cost

$500,000-$750,000

Timeframe

2-3 years

Research Idea Scope

I. Research Problem Statement:
Erosion (runoff) and sedimentation of and from low-volume roads can adversely impact the environment. Many low-volume roads are soil or aggregate surfaced, have steeper grades than many paved roads, and are designed and maintained on narrower rights-of-way with steep fill slopes and back slopes and narrow or non-existent ditches. Runoff from rainfall can lead to erosion of the road surface or ditch bottoms. Drainage channels leading from the roads to nearby watercourses are receptors of soil and rock eroded from unsealed surfaces of these roads. Eroded sediments can adversely affect upland streams, damaging the aquatic ecosystem or increasing the risk of flooding. Low-volume roads can act as intermittent tributary streams in times of high rainfall and can significantly contribute to peak flows in higher order streams.

When these roads are the receptors of agricultural runoff, roadside drainage is impeded, leading to road grade instability. Some agricultural runoff is contaminated with manure and/or chemicals, which can reach downstream receptors and/or kill roadside vegetation, thus exacerbating erosion problems within the right-of-way. Stream crossings may have been adequately designed for hydraulic capacity; however, fish passage and debris flows are often a concern for embankment stability and species habitat.

Not all roads, and not all segments of a given road, cause such problems. However, methods need to be developed to assist road planners and managers in identifying problem segments of roads and applying appropriate mitigation measures to those segments.

II. Research Objective:
The objectives of this research need are to develop simplified tools and procedures to:

1. Measure offsite adverse impacts of runoff from low-volume rural roads, in particular erosion and sedimentation of adjacent drainage channels and watercourses.

2. Assess adverse effects of agricultural runoff to roadside drainage ditches and subsequent problems created for downstream watercourses, roadbed stability, and roadside vegetation. (This includes concerns with disposal of the sediment excavated from the roadside when contaminated by manure and/or chemical runoff.)

3. Identify critical parameters such as road layout and geometry, site soils and geology, regional rainfall intensity and frequency and inappropriate drainage design contributing to the problem(s).

4. Develop tools for identifying problem segments of roads during planning and/or review stages

5. Identify cost-effective mitigation measures that rely on: (a) appropriate modifications to road siting, layout and design and (b) structural and non-structural (bioengineering/ roadside vegetation management) measures to minimize the adverse impacts of road ru

Suggested By

TRB Research Needs Database, AFB30, Low-Volume Roads

Submitted

08/10/2007