Using This Website

Slope Stabilization and Erosion Control Using Vegetation provides coastal landowners and government officials with basic information concerning the nature and use of slope planting techniques to manage soil erosion and shallow seated land movements. Information is introduced on site evaluation, planning, vegetation systems, materials, planting techniques, and general compatibility of the installation with traditional property owner use. This website is a companion document to two other Washington State Department of Ecology websites entitled Vegetation Management: A Guide for Puget Sound Bluff Property Owners, and Surface Water and Groundwater on Coastal Bluffs: A Guide for Puget Sound Property Owners. The online documents should be used together to foster a better understanding and appreciation for the role and maintenance of vegetation along the coastal zone of Puget Sound. The following sections present an idealized scheme of how these websites might be used by landowners and local government.

Coastal Land Owners

Readers who own coastal property and who are concerned about soil erosion control and shallow land movement prevention can use this and other Washington Department of Ecology documents to select and employ general slope protection practices which may be applicable to their property. Additionally, readers can access a wealth of information available through public agencies and library systems. For many situations, professional design assistance should be sought. The information provided in this website provides the basic information necessary to make general planning decisions and simple installations on slopes. The website is not intended as a substitute for professional geotechnical/biotechnical engineering design or site-specific consultation.

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Government Permit Agencies

Readers working for government agencies, whose responsibilities may involve policy creation, geologically hazardous areas, and development/permit application reviews, can use this website to help them determine whether projects address vegetative systems as a viable component of slope stability maintenance. Permitting agencies will find this online document useful in suggesting alternative slope maintenance practices to coastal land owners who are unfamiliar with the advantages of slope planting techniques. This site may also allow agency personnel to better understand the cause and effect relationship of shoreline development and the continuing maintenance of slope stability and erosion control.

Selecting a Slope Maintenance Program

The coasts of Puget Sound contain a variety of landforms which can vary greatly in their composition and historical use. This makes it difficult to cover all of the problems landowners may encounter on their properties in one website. Nevertheless, this site will introduce some general planting techniques that may be used alone or in combination with other revegetation programs and existing natural areas to protect coastal slopes.

It is important for you, the property owner, to understand your site characteristics, and the erosion and land movement processes which may effect it. Only then can you begin to select appropriate protection measures to reduce potential slope erosion and land movements.
The first step in the development of a slope maintenance program is to gather basic site information so that you may better identify and select suitable vegetative treatments for problem slope areas. This checklist will help you identify and organize your slope's key features and characteristics. The background information needed to fill out the checklist is contained in the section - Understanding Your Property. Use the checklist as a summary of your own site evaluation.

Once you have generally characterized the existing conditions and uses of your slope, the next practical step is to determine which slope planting techniques may provide solutions to your identified problems. Use Table 1 as general guide to the appropriate slope protection measures for your site. The sections on the role of vegetation in slope stabilization and erosion control and vegetative planting techniques should be reviewed to determine the specific goals and limitations of each technique.

Figure 1. Typical Puget Sound Coastal Slope Profiles.

This website addresses only the unconsolidated soil portions of coastal zone slopes. Bedrock exposures forming the cliffs of the Puget Sound coastal zone are not discussed in any detail in this website because most vegetation installation techniques are not applicable to these areas. The general shapes of Puget Sound coastal slopes are illustrated in Figure 1 above. Use Figure 1 to recognize some of the slope shapes that are familiar to you. When you identify your general slope shape(s), you can begin to understand the behavior of your property and start to account for erosion and landslide processes which may act upon your slope. You then can implement a number of vegetative slope protection measures discussed later in this online document.

The placement and maintenance of vegetation on a slope is important to a slope protection program. However, there are limits to the stabilization role that vegetation can perform which must be recognized at the onset of the planning process. First, vegetation alone can not control deep seated earth movements that may result from a combination of geologic and environmental influences. Additionally, the placement of vegetative components into actively failing slope areas such as landslides or earth flows can not be expected to have any short-term stabilization benefits until these movements are arrested and the sources of the problem are eliminated.
In cases where the toe of a coastal slope is exposed to all but the smallest of Puget Sound wave energies, you must recognize that vegetation alone will not stop long-term erosion. However, it may reduce the rate at which a slope toe is eroded to a potentially acceptable level.

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Some Useful Resources

For your convenience, we have created several documents to aid in your interpretation of this website. They can be reached via the links below, or accessed at any time using the navigation menu at left.

Key to Applicability and Compatibility Graphics

Use this key to review the slope management techniques introduced later in this publication.

Coastal Property Owner Checklist

This checklist can be printed from this site. Use it to evaluate your property, and determine what steps you need to take to stabilize your shorefront.

General Applicability Chart

Use this chart to evaluate the advantages and disadvantages of various stabilization techniques. It can be printed directly from our site, or downloaded as a pdf.

Plant Selection Guide

A partial listing of appropriate native plants for erosion control and slope stabilization. Use this to choose the plants that best suit your property.

Glossary

Use our handy glossary to look up terms with which you may be unfamiliar.

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