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Environmental Horticulture (Gardening)

Controlling Erosion

Soil erosion is a major consequence of storm run-off from unprotected areas. Sediment constitutes the largest volume of contaminant carried by run-off. Most of the phosphate and pesticides polluting our waterways are attached to soil particles. Therefore, controlling erosion will make a significant contribution to the control of water pollution.

The erosion process is initiated when the impact of falling raindrops or irrigation water detaches soil particles. When there is too much water to soak into the soil, it fills surface depressions and begins to flow. With sufficient velocity, this shallow surface run-off carries away the detached soil particles.

  • Tree roots, small stones or rocks becoming exposed.
  • Small rills or gullies beginning to show.
  • Build-up of silt in certain low areas.
  • Soil splashed on windows and outside walls.
  • The widening or deepening of stream channels.

This destructive process can be controlled by reducing the quantity and velocity of run-off through the use of groundcovers. Groundcovers include any plant material that covers the ground surface so that the soil cannot be seen from above and rain does not strike directly upon it.

Turfgrass is one important type of groundcover, but many other low-growing plants are used this way. These include herbaceous perennial plants and low shrubs. Besides controlling erosion on slopes, the groundcovers fulfill other important functions as follows:

  • Conserve soil moisture and lower soil temperatures during periods of extreme heat.
  • Utilize nutrients in the soil for plant growth, which otherwise could be lost to erosion and leaching.
  • Reduce lawn maintenance and fill narrow, odd shaped areas where mowing and edging might be difficult.
  • Obstructing foot traffic without impeding view.
  • Producing interesting patterns with variation in height, texture, and color.

Significant maintenance is necessary for the first one to three years until the groundcover becomes established. Provide regular cultivation, use organic mulch to control weeds, and fertilize to encourage vigorous growth for good cover; irrigate in times of drought; and provide disease and pest control.

Sod is the most common groundcover. The fibrous roots of turf grasses firmly hold the surface soil and absorb water. Sod also benefits the soil by adding organic matter to improve soil structure and infiltration of water and air.

Newly cut banks and any slopes greater than 12% are best treated with groundcover plantings other than sod, to reduce maintenance. Around buildings, ground covers are superior to paving or structural controls for reducing heat, glare, noise and dust.