Nov 072011
 

 

Retaining walls

The hill came down, the walls went up

 

Before the rains come crashing down, take a good look around your property.  It’s especially important if you are on a hill or have slopes around you.  When water picks up speed it can really create havoc.  Take a look at this hillside. After a number of rainy days, the whole hillside came down into the driveway.  Fortunately, no person and no cars were there when the soil came down.

In an effort to get more light in the property the owners cut down many trees.  The result, light came down and so did the hillside.  They should have made sure the ground was planted and drainage was put in place.  To do it after the soil erodes is much more expensive. In addition to cutting back the hill and putting in retaining walls, we also put drain pipe behind the walls, at the top of the hill and at the bottom.  Water has to go somewhere!  Take a look.

Erosion control for steep hills may mean building retaining walls

Cement block wall at the bottom and wood retaining walls will hold back this hill

Construction of the retaining wall

Retaining wall in process

There's still too much soil, and erosion can be a problem

Cement block wall is not high enough, and soil needs to be removed

After the walls are built, it is important to plant for soil coverage.  I use seeds for immediate coverage and plants for long term coverage.  At the top of the hill we put in a swale to redirect the water away from the main walls. We covered it with erosion control blankets.  They are both 100% biodegradable, but they are slightly different. One is thicker and made of coconut fiber and the other has straw put between cotton netting. The thick mat is better for stronger erosion control and the straw allows better germination of seeds.

Two types of erosion control blankets - coconut and straw

The blanket on the left has straw and the blanket on the right is coconut fiber.

Swale

A long swale covered with netting and also planted with seed

For quick germination I used rye grass, Dutch white clover, vetch and California wildflower mix, with extra California poppies. We were lucky with early October rains that helped with excellent germination.  If you don’t expect rain, you should water the seeds to take advantage of warmer weather in the early Fall.  Once the winter rains come it gets too cold for most seeds to germinate.

Erosion control seed mix

Rye grass, Dutch white clover, Vetch and Wildflowers

Seeds germinating through straw mulch

Straw mulch holds the soil in place and protects the seed

 

Tomorrow I’ll talk about other simple erosion control  methods.

Curving path on steep hill

Using plants and curving path for hillside erosion control

 

 

 

 

 

  2 Responses to “Erosion Control on Steep Hillsides – Do it before the rains come!”

  1. Wow, that is a steep hill! I’ll be interested to read your hillside erosion control, as my yard is set on a hill but we really don’t want to put in a retaining wall..

    • I wish I had a picture of the hill when it first came down. It was a huge pile of mud at the bottom. I believe that diverting water in different ways helps to hold hillsides. Tomorrow you’ll see photos of steep hills with very small retaining walls, and they really work.

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