Washington State Department of Ecology
about slides
slide signs
what to do
getting help
site info
frequently asked questions
slope stability maps
slide show
frequently asked questions

Frequently asked questions
Answers on buying, building, insurance, drainage, bulkheads and more

Before I buy shoreline property on a bluff, who should I contact?
How far back from the edge of a coastal bluff should I build?
A landslide destroyed my beach stairs and my bulkhead.
Will my insurance cover it?
Are trees on a slope good or bad?
What about financial or professional assistance for slide victims?
I have had two slides. The estimated cost for proposed engineering is huge. Do I have options?
How do I know who the good consultants are?
A contractor has recommended that I replace my timber bulkhead with a new rock seawall. Is this wise?
What about hydroseeding after a slide?
I've noticed cracks around my home. Should I be concerned?
Will tightlines protect my bluff?

Before I buy shoreline property on a high bluff, who should I contact?
First, check with the local planning department about building limitations, setbacks, vegetation removal, septic placement, drainage, and requirements for structures along the shoreline. Second, investigate local government sources for information on past sliding in area. Finally, contact a qualified engineering geologist or geotechnical engineer familiar with coastal slopes and your area. These professionals are trained to look for signs of sliding and will be able to estimate the likelihood and type of slides that might occur. Ask them to evaluate the wisdom of purchasing this property. Get advice on how and where development should be sited. Seek out other information on landsliding. Check the slope maps and information in this Web site. Use caution when buying waterfront property and remember, "great views inspire blindness."

How far back from the edge of a coastal bluff should I build?
Safe recommended setbacks range from 30 to 40 feet to a distance equal to twice the height of the bluff. The setback should reflect the rate of erosion of the toe of the slope due to river or marine erosion and the nature of sliding likely. Also, setbacks should reflect more than just risks from landslides. Along environmentally sensitive shorelines, a larger setback may be required to protect ecology, water quality, and public resources.

A landslide destroyed my beach stairs and my bulkhead. Will my insurance cover it?
Probably not. Most insurance policies exclude damage caused by earth movement or landsliding. If you have purchased flood insurance (federal or private), some damages may be covered in some circumstances. Read your policy carefully.

Are trees on a slope good or bad?
It depends. In general, trees help remove water from soils and sturdy roots help stabilize a slope. However, in the event of a slide, trees can become lethal projectiles. Should you remove trees? There are many factors to consider: stability of your slope, tree species, age, health of the tree, current stability of the tree, position on the slope, and surrounding vegetation. For more information about tree removal consult, Managing Vegetation on Coastal Slopes.
managing vegetation on coastal slopes

I've had a slide, but can't afford a consultant. Are there any sources for financial or professional assistance for slide victims?
Contact your local Cooperative Extension Office, Conservation District, or local Public Works Department. They may not have the resources or expertise to recommend solutions and should not be expected to design an engineered fix, but they may be able to suggest possible courses of action or lead to you to other assistance. If the landslide occurred during a state or federally declared disaster, such as in early 1997, emergency management agencies may be able to provide reconnaissance-level professional assistance and relief in the form of temporary living expenses or low-interest loans. Property owners with federal flood insurance may be able to seek reimbursement for slide related damages in some cases. Detailed reports and engineering solutions, however, will still need to come from private consultants and contractors.

Slides on my waterfront bluff are threatening to undercut my deck. A geotechnical engineer has recommended soil nailing, horizontal drains, a new seawall, and a cribwall. The estimated cost is huge. Do I have options?
Maybe. As with any large project, you may wish to get a second opinion or another estimate. Considering the circumstance however, the recommendations may be appropriate. Given the proximity of your home to the edge of the bluff and the high cost of trying to stabilize the bluff, you may want to investigate relocating your house landward. Although certainly not cheap, such an action might be cheaper in the long run, greatly increase your piece of mind, and avoid many of the adverse environmental impacts that come from extensive engineering of the shoreline and the bluff.

How do I know who the good consultants are?
Select geologists and geotechnical consultants as you would other professionals. Call several, ask tough questions, and trust your instincts. Ask friends and neighbors for references. Do not hire a consultant simply because they tell you what you want to hear. In the case of geotechnical engineers, check with the state engineering board to see if there are complaints registered.
getting help
getting help

I recently had a landslide along my bluff. A contractor has recommended that I replace my old timber bulkhead with a new rock seawall. Is this wise?
Evaluate the cause of the slide before seeking a solution. If the cause of the instability is higher on the slope, a new bulkhead may do little to increase safety. In your situation, a slide has occured despite the existing bulkhead. Where erosion of the toe of the slope is contributing to the slide, some sort of toe protection may be warranted. A rock seawall is one of several options. Get the opinion of a second contractor who builds another type of structure -- or better yet, an engineering geologist or geotechnical engineer who can assess the cause of the problem and recommend a broader range of solutions. Concerns about the effects of bulkheads and seawalls on shoreline ecology has increased. In some cases, it may be preferable or even necessary to look at other approaches.

My bluff slid this winter. A consultant recommended that when the weather improves this spring, we remove the plastic sheeting currently covering the bare soils and hydroseed. Is this an appropriate solution?

For large scale planting on hard-to-reach slopes, machines called hydroseeders, which spray mixtures of seed, water, and mulch may be used. Hydroseeding grasses can provide some protection from surface erosion on gradual slopes. However, on steep slopes prone to severe erosion and gullying, hydroseeding may not be effective. Hydroseeding alone is also not adequate for landslide stabilization. The shallow, fine root systems of grasses do not strengthen the soil profile significantly and limit landsliding. For more information, consult, Controlling Erosion Using Vegetation.

My home is located about 75 feet from the edge of the bluff. Recently, I've noticed cracks developing in the earth around my home. Should I be concerned?
The appearance of cracks is not in itself cause for alarm. Cracks often develop in some soils when the soil dries out, typically in the late summer, and does not indicate any serious underlying problems. If the cracks are large, continue to expand in wet weather, or show differential movement (one side is higher than the other), then monitor them carefully and consider speaking to a geologist or engineer. Cracks associated with earth movement tend to be parallel to the edge of the bluff or the slope, may form large curves, and generally result in one side dropping relative to another. Once cracks form, they allow water to enter soils more rapidly and may increase instability. They will typically increase in size during wet weather (although there are exceptions). If you have any doubts, seek professional advice.

We bought a home that overlooks the Sound from a steep 80-foot bluff. There are signs of past slides and the previous owners installed a tightline that carries water from the downspouts to the beach. Is this an effective solution?

We typically recommend that residents of bluff-top property avoid adding to the groundwater near or on the face of the bluff, and therefore not aggravate instability. Routing surface runoff to the beach in a tightline (a closed pipe) is standard practice, although the degree to which it helps is highly site dependent. Tightlines need to be installed carefully and inspected frequently. If they fail, which they typically do in the wettest conditions, they may concentrate enormous flows in exactly the wrong place. Tightlines can be damaged by wind, falling tree limbs, and small slides. They can also be clogged by animal nests, ice, or debris. Many landslides occur where tightlines and drain pipes fail. Tightlines can be an eyesore (you may see bluffs with black and white plastic pipes hanging over the edge). They can also carry surface water that can contain oils, fertilizers, household chemicals, and other contaminants directly to the beach. More about drainage...
drainagebroken tightline on bluff face

US Geological Survey
Landslide Preparedness
home | about slides | warning signs | what to do | prevention | help | faq | maps | slide show | site info | sea program home | ecology home