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The rainy season is upon us and this means taking the proper precautions to prevent soil erosion throughout the landscape. Heavy rains can wash away valuable soil nutrients and the topsoil which plants need for proper growth. More often than not, this displaced soil ends up in our local streams and lakes and is filled with pollutants such as chemicals, fertilizers, oil and grease, animal wastes and bacteria which can be deadly to plant and animal populations. Additionally, silt build-up on the bottoms of streams can make it difficult for many species of fish to lay their eggs and reproduce. With that being said, what can we do to help prevent erosion, keep our landscapes beautiful and most importantly, help our environment stay healthy?
 Keep Slopes Covered in Vegetation - This is probably the best way to slow erosion. Plant roots stabilize the slope and act as a protective cover to reduce the impact of rain drops on the soil surface. Plants with a spreading growth habit are great for covering hillsides. Plants to the right include: Thyme, Mexican Sage, Yarrow, Purple Hopseed Bush, and Pepper Tree.
Variety of Plant Root Depths - Having a variety of trees, shrubs, perennials and groundcovers with different root depths helps to tie the surface of the soil to the bedrock below. Generally the bigger the plant the deeper the root depth.
Blankets and Mats - These can help support the soil surface while plants are growing in. Many are biodegradable and will actually help provide a good start for plants by keeping the soil moist, protecting seedlings and adding nutrients to plants as the mats degrade. Make sure they are in contact with the soil and securely fastened to the slope. Cover the mats or blankets with bark mulch if possible for aesthetics and to slow the degradation of the mats and blankets.
Mulch - Mulch alone can be an effective soil erosion control method on gradual slopes with less than 3:1 gradation.
Terracing and Retaining Walls - Minimize the steepness and length of a slope by creating terraces with retaining walls. This will help prevent soil erosion from occurring, allow water to be retained for plant use, ease maintenance headaches and add aesthetic value to your property.
 Drainage Swales - Creating drainage swales can redirect water from roofs, patios, decks, and driveways away from the landscape to an area where it can be disposed of properly. Dry creek beds are an attractive way to dress up drainage swales.
Preventing erosion is always better and far more effective than reversing the damage it creates later. By following the methods listed above we can all help to keep our environment healthy, by preventing soil erosion.
Resources:
Groundwork: A Handbook for Erosion Control in North Coastal California by Liza Prunuske
Soil Erosion and Hydroseeding, Jan/Feb 09 issue, "Blankets and Mats: Roll with the Times" by Elizabeth Lexau
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Sincerely,
Suzanne Morrison
EARTHSCAPES
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