Environmental Management, Assessment, Mitigation, Restoration, Education & Outreach
If you are considering building on a
bluff along the Puget Sound shoreline (or on a low-bank lot backed
by a steep slope), minimizing clearing & grading and preserving existing native soils &
plant communities
during development is the
least expensive and most effective way
to forestall future stormwater, erosion and shallow landslide
problems on your new property.
Preserving natural drainage systems will
help reduce
the need for & expense of designing and implementing complex
stormwater management measures. You will also improve water quality,
preserve wildlife & salmon
habitat, and maintain
the beauty
of the region.
If
your bluff property has already been developed your new home may
have an inadequate setback, stormwater runoff problems, infestations
of invasive plants, topped trees, and extensive lawns. You may be
inheriting problems from past poor management practices. Lawns which
extend to the bluff edge can contribute to stormwater runoff &
erosion problems and destabilization of marginal slopes. A
combination of adopting better management practices, structural
drainage measures, and vegetation enhancement may help to improve
conditions.
Whether you are developing a new home or improving an existing site,
using native plant species to create a
distinctively ‘Northwest’ residential landscape can help to reduce
stormwater problems & erosion and minimize conditions which may
trigger landslides.
Plantings of low-growing native species along the bluff edge (known
as shoreline buffers)
-
about 15-30 feet in width -
and reducing
the extent
of lawns
are two
of the simplest
and most effective
steps that
shoreline owners can
take to protect
their property and help to
keep
the
The
educational resources & references
provided here
will help
you
learn about your property and aid in development of
a management strategy
best suited
to your
particular situation and
site
conditions.
GETTING EDUCATED
Before you alter the shoreline,
familiarize yourself with the characteristics of the land,
shoreline processes, geology, hydrology, topography, and landscape
vegetation. Understand the applicable regulations. Get advice on how to
proceed. The resources below will help get you started.
RESEARCHING
YOUR SITE
•
https://fortress.wa.gov/ecy/coastalatlas/
•
https://fortress.wa.gov/ecy/shorephotoviewer/
• Landslide Hazard Maps –
Washington Department of Natural Resources (DNR)
https://www.dnr.wa.gov/programs-and-services/geology/geologic-hazards/geologic-hazard-maps
• Geologic Information
Portal – Washington Department of Natural Resources (DNR)
https://www.dnr.wa.gov/geologyportal
•
http://lidarportal.dnr.wa.gov/#47.98974:-122.37716:16
• Area Maps and Property
Information – Municipal &
County Development Services
HELPFUL WEBSITES
• Dept. of Natural
Resources, Div. of Geology & Earth Resources -
Learning about Landslides
http://file.dnr.wa.gov/publications/ger_homeowners_guide_landslides.pdf
• Shore Friendly –
Washington Dept. of Fish & Wildlife
• Shore Stewards – WSU
Extension
http://shorestewards.cw.wsu.edu/
•
https://fortress.wa.gov/ecy/coastalatlas/
•
https://ecology.wa.gov/Water-Shorelines/Shoreline-coastal-management/Hazards/Puget-Sound-landslides
•
• Dept. of Natural
Resources (DNR), Div. of Geology & Earth Resources- LIDAR Portal
http://lidarportal.dnr.wa.gov/#47.98974:-122.37716:16
HELPFUL PUBLICATIONS
•
Surface
Water
& Groundwater
on
Coastal
Bluffs: A
Guide
for
https://fortress.wa.gov/ecy/publications/documents/95107.pdf
•
Vegetation Management: A Guide for
https://fortress.wa.gov/ecy/publications/documents/9331.pdf
•
Your Marine Waterfront
http://wdfw.wa.gov/publications/01791/
•
Shore Stewards Guide for Shoreline
living
WSU Shore Stewards Guide for Shoreline
Living
•
Marine Shoreline Design Guidelines
http://wdfw.wa.gov/conservation/habitat/planning/ahg/
WISE
DEVELOPMENT PRACTICES
•
Low Impact
Development Techniques
for
Wooded Shoreline
Home
Sites
•
Preserving Native Vegetation to Reduce Stormwater Impacts
RESOURCES FOR USE OF VEGETATION FOR
STORMWATER, EROSION, AND SHALLOW LANDSLIDE CONTROL
•
https://www.wnps.org/landscaping/index.html
•
https://green2.kingcounty.gov/gonative/Article.aspx?Act=view&ArticleID=28
•
Resource Postings from “Landscapes
on the Edge”, a 2-day workshop convened by the UW Botanic Gardens,
November 2016
https://botanicgardens.uw.edu/about/blog/2016/09/22/landscapes-on-the-edge/
•
Educational postings on the Greenbelt Consulting Website
Restoring
Native Vegetation on Coastal
Bluffs
in
Puget
Sound
– An Overview
Slope
Revegetation:
A Checklist
of Factors to
Consider
Value, Benefits
and Limitations
of Vegetation
in Reducing Erosion
GET ADVICE
• Local Planning and
Public Works Offices
•
• Engineering Geologist
• Geotechnical Engineer/
Civil Engineer
• Forester, Restoration
Ecologist, or Arborist
A FEW DOS AND DON’TS TO HELP
PROTECT YOUR PROPERTY
DO
AN OUNCE OF PREVENTION IS WORTH A TON OF STRUCTURAL REPAIRS
DON’T
DON’T CREATE TOMORROW’S
CRISIS TODAY
Coastal Property Characterization & Drainage Checklist
Because of the impact to
coastal slopes, it is important that you understand the specific slope
characteristics, hydrogeology, vegetation conditions, coastal
geomorphology, shore processes, and drainage conditions influencing your
site. Become familiar with the potential erosion and slope instability
processes effecting your area. Identify sources contributing water into
and onto your slope.
If you can identify the
proximate sources of erosion and slope instability, as well as surficial
and groundwater sources, you can then take steps to control some of
these sources.
The checklist below can
help you organize the observation of surface water and groundwater
conditions on your property.
Slope Characteristics
Slope Height:
·
less than 10 feet
·
10 to 50 feet
·
greater than 50 feet
Slope Angle:
__ degrees (see
“Relationship
between degrees, percent slope, and ratio to express slope
gradient”)
Slope Vegetation:
·
bare soil areas
·
vegetation cut, removed or cleared
·
topped trees
·
mature vegetation (trees, shrubs and
ground cover)
·
water loving plants (horsetail,
skunk cabbage, willow, salmonberry, etc.)
·
Curved Trees
·
Presence of invasive plant species
Slope Geology:
·
sand or sand and gravel (glacial
outwash)
·
hardpan (glacial till)
·
fine sediments (glacial drift)
·
inter-bedded silt/clay
·
rock
Erosion Indicators:
·
indications of sheet-flow
·
rills & gullies
Landslide Indicators:
·
recent slide
·
bowl-shaped slope configuration
·
hummocky ground
·
leaning trees or bowed trunks
·
areas of low brush (blackberry)/bare
areas
Surface Water/Storm Water Flows
·
Sheet flow from:
o
driveway
o
parking area
o
lawn
o
off site
·
Roof downspouts empty:
o
onto ground
o
into buried pipe
o
other
·
Outlet for downspout pipe:
o
into soil or on surface of slope
o
tight-lined down slope
o
unknown (test with hose)
·
Other pipe/culvert
o
discharges:
o
onto slope
o
tight-lined down slope
o
other
·
Areas where surface water disappears
into ground?
o
Yes
o
No
·
Seepage/water noticed along beach
access path?
o
Yes
o
No
Coastal Zone Atlas:
·
landslide area
·
unstable
·
intermediate stability
·
stable
Beach Access:
·
stairs
·
wide path/road
·
tram
·
narrow path
Site Groundwater
Groundwater Observation:
·
seepage on slope: crest, face, or
toe?
·
wet soil zone: crest, face, or toe?
·
vegetation indications of wet soil:
crest, face, or toe?
Location of observed groundwater:
·
Near-surface soil seepage 1 to 3
feet below crest of slope
·
Groundwater seepage 5 to 10 feet
below crest of slope
·
Groundwater seepage on slope face
more than 10 feet below crest or at slope toe
Surface Water Features:
·
stream channel
·
ponds/wetlands - how far from crest
of slope?__________
·
flows down/over the slope
·
tightline down slope
·
erosion evidence: rills, gulleys,
etc.
Other Site Features
·
Septic system
o
between house and slope
o
behind house
o
N/A
·
Irrigation system
o
any leaks
o
summer use only
o
control valve off and lines drained
in winter
·
Downspout infiltration system
o
between house and slope
o
behind house
o
not applicable
·
Landscape yard drains
o
tight-line down slope
o
discharge onto slope
o
unknown (test to find out)
·
Landscape pools/ponds/fountains
o
between house and slope
o
behind house
o
not applicable
·
Hot tub(s)/swimming pool(s)
o
between house and slope
o
behind house
o
not applicable
·
Where are tub/pool/pond/fountains
drained?
o
Into a tight-line drainage system
o
onto slope
o
below slope
o
onto ground
o
unknown (test to find out)
Distance of structures & other at-risk infrastructure features
from slope crest (e.g. house, septic field, etc)
NOTE: This material has been updated, adapted, & substantively revised
from outreach material originally developed by the Snohomish County
Marine Resources Committee --
http://www.snocomrc.org/projects/coastal-landowners/
and the Washington Department of Ecology –
https://ecology.wa.gov/About-us/Get-to-know-us/Our-Programs/Shorelands-Environmental-Assistance