Ditches created through landscaping procedures, near building sites, on roadsides or elsewhere are susceptible to erosion. Erosion occurs when water carries soil away, often making the ditch deeper and the remaining soil less stable. Near roadsides, ditch erosion can undermine the stability of the road. Erosion also carries soil and sediments into waterways, leading to water quality problems. Landowners and land managers must employ techniques to help prevent ditch erosion.
Gently Sloped Sides
Steep sides in a ditch channel more water through less space, which leads to erosion. When constructing a new ditch or performing maintenance on an existing one, create gentle slopes to the ditch sides and leave the bottom flat or slightly curved. The ratio of height-to-vertical increase on ditch sides should be two-to-one or flatter. For every unit (inches, for example) of increase vertically, there should be at least two units of horizontal increase.
Rushing water in ditches increases erosion. Stone check dams constructed at intervals through the length of the ditch slow the rate for water flow. Check dams will also allow sediment to settle out of the water so it does not pollute natural waterways.
Vegetation stabilizes soil through the plants' root systems and helps prevent erosion. Leave existing vegetation intact in ditches whenever possible. Seed new ditches with grass, and mulch to hold seeds in place until vegetation is well established.
Erosion Mats, Blankets and Netting
Products made of natural materials such as coconut fibers that line ditch sides are available commercially through landscape suppliers. These products help stabilize the soil and can often be left in place. Erosion control products also help promote plant growth, which will further secure the ditch.
Line the ditch with graded rock, called riprap, to stabilize the soil. Rocks must be large enough to stay in place through rushing water.