AKRON — The question is often asked, “Why do many counties prefer open roadside ditches along county roads, instead of enclosed pipe drainage systems?”
Here are some of the reasons, according to Greg Bachman, a professional engineer, surveyor and Summit County engineer.
One of the purposes of a roadway drainage ditch is to prevent unsafe accumulations of rainwater on the roadway surface.
An open ditch allows water to move fully away from a road surface. In contrast, a piped storm sewer system uses the edge of the roadway surface if there is a curb, or a shallow swale over the former ditch to convey the water until it reaches a catch basin or other point of interception.
An open ditch also continuously intercepts rainwater flowing toward the roadway from adjacent land. For these reasons, a roadway drainage ditch is less likely to allow accumulation of water on or near a roadway surface than a storm sewer system.
Another purpose of a roadway drainage ditch is to drain water from under the roadway. The base is the foundation for supporting the load of traffic on the asphalt roadway. If water becomes trapped in the base, it weakens the structure of the roadway, leading to premature failure of the roadway.
In addition, during cold weather, freezing and thawing of water trapped in the base under the pavement causes rapid deterioration of the pavement. An open ditch of sufficient depth provides continuous drainage of the base.
An open ditch has more capability than a piped system to reduce flooding resulting from heavy rainfall. During an extreme rainfall, flow in a roadway drainage ditch is usually limited by driveway culverts or water elevations at discharge points, such as intercepting streams.
When that happens, each roadway ditch becomes a small detention basin, storing excess water until discharge capacity becomes available. A piped system does not have capability to store excess water. A piped system also accelerates water flow, making downstream flooding conditions worse.
An open ditch helps maintain healthy water quality in receiving streams. Vegetation in a roadway drainage ditch provides valuable filtering of water.
Roadways gradually accumulate rubber tire wear, lubricants, metal particles, rust fragments and other substances from the wear and weathering of motor vehicles. These substances, as well as roadway materials loosened by wear and weathering, are washed from roadways by rainwater.
An open ditch has more capability than a piped system to reduce flooding resulting from heavy rainfall.
Ditch vegetation helps to trap these substances and reduce flow rates, promoting settlement of solid particles and preventing them from entering the natural waterways.
Mowing of roadside ditches should be kept to a minimum in order to maximize filtering. Ditches reduce flow rates and increase storage of excess rainwater, which helps reduce downstream erosion and the impact on stream habitat caused by high concentrations of suspended solids.
The detection of illicit discharges is easier in open ditches than in closed piped systems. Environmental Protection Agency rules require that nonrainwater discharges be eliminated from urban drainage systems. Such discharges include failing septic system discharges and disposal of solvents, motor vehicle fluids and cleaning products.
Piped drainage systems, including storm sewers, catch basins, manholes, headwalls and underdrain piping are much more costly to construct than roadside ditches. If a piped drainage system is constructed without adding an adequate underdrain system, additional costs are incurred for roadway repair and reconstruction due to roadway deterioration caused by the inadequate base drainage.
The Summit County engineer maintains over 35 miles of dedicated stormwater drainage ditches throughout Summit County. Many of the ditches relate back to Ohio’s agricultural past and were created to provide sufficient drainage for the farmland in Summit County.
As Summit County became more urbanized, subdivisions and communities grew up around these drainage devices. They can be found along the borders of allotments, or even running through industrial parks.
It is important that all county ditches be kept clear of obstructions that would impede the flow of water. Do not dump grass clippings, leaves or other debris into either roadside ditches or county ditches.
At times, natural obstructions such as trees or tree limbs, beaver dams, brush or bushes, may fall into ditches. These obstructions, if left unattended, may cause a ditch to become clogged and overflow.
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