What it is
Two-stage ditches are an alternative design for open channel systems, which are typically constructed and maintained as a trapezoidal shape. The two-stage design is a more sustainable approach to surface and subsurface drainage management.
How it helps
Benefits of a two-stage ditch over the typical agricultural ditch include both improved drainage and ecological function. The two-stage design improves ditch stability by slowing down water flow and reducing the need for maintenance, saving both labor and money. It also has the potential to create and maintain better habitat and water quality conditions for the waters into which our drains flow, such as the Gulf of Mexico or Lake Erie. This is done by minimizing the amount of sediment and nutrients (such as phosphorus and nitrogen) that are transported from ditch to stream to river to sea. The overall return on investment should consider the long-term benefits of the conversion of a typical drainage channel into a two-stage channel.
Like many conservation practices, a two-stage design is better suited in certain locations. Consulting a knowledgeable professional such as your county engineer, local Soil and Water Conservation District and/or a professional engineering company is a must before any earthwork is performed. Having an accurate survey and engineering design will help you determine the costs associated with constructing a two-stage ditch.
A significant amount of work/resources goes into the proper design and construction of the two-stage channel. Special consideration should be given to the size and elevation of the constructed benches, transitions into and out of the two-stage section, and areas near culverts or crossings. Rock chutes can be installed where concentrated surface flows enter the channel from the field or from drain tiles. After construction, care should be taken to establish and maintain vegetation on disturbed areas to prevent erosion. If designed and installed properly, sediment clean out from the bottom of the ditch should be much less than a typical drainage channel.
The benefits of a two-stage ditch over the typical agricultural ditch include improving drainage and ecological function by reducing erosion, scouring and flooding. The two-stage design improves ditch stability by spreading out and slowing down water flow and reducing the need for maintenance, saving both labor and money. If designed and installed properly, sediment clean out from the bottom of the ditch should be much less than a typical drainage channel.