LSU AgCenter's Weekly Message

Managing Erosion in the Landscape – Part 1

Many people encounter erosion problems at some point. While much of our land in Louisiana is quite flat, some is not. Furthermore, erosion can occur with even a slight slope or, in the case of wind-driven erosion, no slope at all.

Erosion of topsoil is a problem for plants, since this layer of the soil tends to have greater nutrient and organic matter contents than those below it and is naturally well-suited for plant growth. For those not particularly interested in plant growth for its own sake, erosion can affect the ability to drive a vehicle safely or walk around your property easily, as well as the stability of houses and other buildings.

Wind contributes to erosion, especially in dry climates and, more relevant to some parts of Louisiana, where soils with high organic matter contents have been drained. However, water is the more common agent of erosion in Louisiana and worldwide. Water can cause erosion when it hits the soil as droplets during rainfall or irrigation, or as it flows over the surface of the soil.

Besides the amount of rainfall that we get and the intensity of rainstorms, a number of other factors affect how much erosion occurs on a site. I discuss some of these in this article. In the next article, I’ll go into more depth about a factor over which people often have some control: how much cover is on the site. Soil cover includes plants, mulch, and other materials.

One of the most obvious factors that affects how much erosion occurs is the steepness of the slope. Other factors being equal, a steeper slope will experience more erosion than a less steep one. The length of the slope affects erosion, as well. More erosion will occur when there is a longer slope than when there is just a short length of slope of the same steepness.

Terracing involves reducing the steepness and the length of slopes. In a landscape, treated wood or masonry retaining walls can be used to form terraces. Assistance from a landscape architect or engineer may be needed when taking on a terracing project.

Various soil characteristics influence how much erosion occurs. Soil texture is one. Silty soils are more prone to erosion than those with high clay or sand contents (except very fine sands, which are also highly erodible).

Soil with stable aggregates is less prone to erosion. Organic matter helps hold soil particles together. Here in the hot, humid south, organic matter tends to break down quickly, so many of our soils naturally have low organic matter contents. Practices that increase organic matter – such as mulching, applying compost, and cover cropping – may help reduce erosion in the long term.

Where a large volume of runoff is expected, it may be best to make channels through which water can move and in which erosion can be managed. This could be on a substantial slope, but it could also be at the base of a gutter downspout.

In the next article, I’ll address soil cover, including some plant options for slopes.

Let me know if you have questions.

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Dr. Mary Helen Ferguson is an Extension Agent with the LSU AgCenter, with horticulture responsibilities in Washington and Tangipahoa Parishes. Contact Mary Helen at mhferguson@agcenter.lsu.edu or 985-277-1850 (Hammond) or 985-839-7855 (Franklinton).