Mitigating Erosion
When you are deciding about which site to select for the project, you need
to consider soil erosion. There are two aspects to consider. The first is how the
site can be developed to prevent erosion from occurring. The second is what can
be done to prevent the erosion that does occur from causing harm to the
environment. We call this erosion mitigation. Here are some ideas to consider.
You can do some research to find out more details.
Preventing Erosion
I) Vegetation: Vegetation is the plants: trees, bushes, ground covering and
flowers
Trees, bushes, grass and other ground covers all help
prevent soil erosion.
http://www.dailykos.com/story/2007/3/9/105451/0047/237/309966
Things to consider about vegetation during the construction project:
*You want to design the project so that you remove as few of the existing
plants as possible. Leave trees and shrubs that will help prevent erosion of the
topsoil.
* If vegetation is removed during construction, use a temporary means of
covering the ground to hold down the soil . Some ideas include:
1) Plant grasses which grow quickly and help prevent erosion.
Using grass to control erosion in Ethiopia
http://www.vetiver.org/g/soil_erosion.htm
2) Cover the ground with mulching material such as bark, grass
clippings or leaves. These all help provide a good start to more permanent trees
and shrubs that you may plant later. (Mulching material is a protective cover
placed over the soil to retain moisture and reduce erosion. )
3) Place burlap, jute or plastic mats over the exposed land to help
hold down the soil and prevent erosion.
Using burlap bags to slow erosion
http://thetanglednest.com/2010/02/upcycled-burlap-bags-in-the-garden-and-farewell-to-grass/
Using Jute netting to slow erosion
http://www.outsidepride.com/landscape-fabric/erosion-control.html
Be sure to protect the existing vegetation while construction is happening. You
don't want to damage the plants that are still standing.
Things to consider about vegetation after the construction project:
* Plant a variety of types of vegetation such as:
1) ground covers that creep along the ground and cover lots of area.
http://www.ehow.com/list_6555097_low-growing-ground-cover-plants.html
2) trees that have deeper roots to hold the soil in place.
3) plants that are native to the area. Native plants take less water
and are most likely to do well in the soil.
Western Hemlock
http://www.bomengids.nl/uk/hemlockdouglas.html
picture from the Skokomish River Valley 2011.
4) Plant windbreaks of trees or shrubs to reduce soil loss from
blowing wind.
This hedge is a windbreak for the soil behind it.
http://www.derryleatrees.com/id2.html
*Be sure to consider the slope when doing the planting. You want to be
sure that the new plants will survive. The steepness of the slope affects
what type of plants should be planted and if the plants will survive.
II) Things to consider about the building site:
1) What type of soil does your site have. Will this soil easily erode?
2) Consider how the water drains off of the land.
How does the water naturally drain off of the land? (This is called
the drainage pattern.)
Will the new buildings let the water continue draining in this same
way?
If the drainage pattern needs to be changed, how will the new
drainage paths affect the surrounding land? Where will soil eroded
from the site likely be deposited?
3) Consider the slope of the land. (Slope is how steep the land is.)
*Will the building project need to change the slope of the land by
leveling some of the ground? If so, how will the changed slope
affect the erosion? Where will soil eroded from the site likely be
deposited?
If the slope is steep, more erosion will occur. If you level part
of the land, will you cause erosion on the land to slow down?
Will changing the slope of part of the land cause greater
erosion in the parts that are still steep? Will leveling part of
the land cause standing water or flooding on these parts of the
property because the amount of water has no natural drainage
pattern?
http://www.crse.org/SteepSlopes.html
4) Create structures to help control erosion:
*Terracing ---One method used to minimize or lessen the steepness
of the slope and help prevent erosion on the land where you are
building is terracing. Terracing breaks the slope into several
slopes that are shorter and less steep.
These pictures show examples of terracing:
http://renovatemyspace.com/projects/?p=35
http://marshfence.com/walls.html
*Diversion structures -- this helps direct where the water
flows. Rock walls and brick walls are examples of diversion
structures.
http://www.specifile.co.za/NewWeb/Compendium/B362-01.HTM
picture from Skokomish River Valley 2011
5)Timing of Construction: Consider when the actual project will be done.
* Building in the spring or summer may cause less erosion. Can you
plan the actual work so that the rains are less likely to cause
erosion during construction when the land is more exposed to
rain and wind?
These
pictures show standing water in the Skokomish River Valley during a rain storm in
February 2011.
Websites to get you started thinking about soil erosion and controlling it:
What You Can Do to Control Erosion and Protect Your Property:
http://www.abag.ca.gov/bayarea/enviro/erosion/eyoudo.html
Landscape planet: About Erosion Control:
www.landscapeplanet.com/maintenance-1.htm
New Construction and ground coverings:
http://www.nrcs.usda.gov/feature/highlights/homegarden/construct.html