Erosion
Preparing for Winter
Rich Casale
CPESC #3 / District Conservationist, USDA Natural Resources
Conservation Service
The sound of falling rain heralds new problems
for those who either suffered property damage from the 2008 Santa
Cruz County wildfires or who live downstream of fire-damaged
watersheds.
If you are concerned about the possibility of
erosion, mudslides, flooding, and other related winter-storm
impacts, here are some rules that may help you safeguard your
property and family.
Prepare
for winter
Keep it under cover. Protect existing plant cover and
establish vegetative cover on bare or disturbed soil and slopes. Use
plant materials and mulches to protect soil and slopes from the
impact of falling rain and storm-water runoff.
Do not disturb soil and slopes during the rainy season.
Slopes and soil are more susceptible to instability and erosion when
vegetation is removed or disturbed, and when soil becomes saturated.
Improve drainage facilities and potential runoff arteas on private
roadways, long driveways, and fire breaks, especially in
fire-damaged areas. Create release points to protect down
slope areas from erosion, slope failure, and flood hazards.
Use this 4-D formula when dealing with drainage
and runoff issues.
Decrease
volume and velocity of runoff by providing velocity dissipation,
rock, or other prepared outlets at culvert and drain outlets. Break
up large volumes of runoff coming from roof tops and landscape into
smaller less erosive forms.
Detain
runoff and store for later use to lessen impact on saturated soil
and slopes during peak storm events.
Dissipate
runoff wherever concentrated flows come in contact with bare soil or
steep slopes by installing (grass, mulch, rock aprons, etc.) that
spread runoff and help reduce erosive capacity of soil and runoff
volumes. Install velocity dissipaters at culvert and drain outlets
to prevent soil erosion.
Divert
runoff if all else fails. Divert with extreme caution. It may be
helpful to re-route runoff and drainage away from unstable slopes,
eroded areas,
unprotected soil, etc.
Monitor and maintain existing and planned runoff-, erosion-, and
sediment-control measures (including vegetative cover) before and
throughout the rainy season. Correct deficiencies as soon
as possible. Leaf litter may be a serious problem for roof,
driveway, and landscape drainage systems.
Use emergency or temporary practices such as sand bags, brush and
slash, plastic sheeting, and hand-dug drainage ditches with extreme
caution. Do not install without professional guidance.
Covering slopes with plastic sheeting or dumping brush into gullies
or other eroded areas is almost always the wrong thing to do. An
improperly designed and placed emergency action can be worse than
doing nothing. In fact, emergency measures may cause new hazards or
problems, and provide a false sense of security.
Prune or remove high-hazard, fire-damaged trees that might be living
structures before winter storms, but don’t remove healthy or
slightly damaged trees unnecessarily. Tree root systems
are still holding soil and slopes in place. Tree cover protects soil
from the impact of falling rain and reducing winter runoff.
Protect against rock slides. Debris barriers are
effective in capturing smaller rocks but larger rocks will require
more substantial measures. If there is a threat of large rocks
releasing from slopes on your property or adjacent properties, seek
professional assistance. Contact the USDA Natural Resources
Conservation Service or the Resource Conservation District of Santa
Cruz County for advice.
Work with neighboring property owners when determining permanent
solutions for drainage and runoff problems. Runoff
normally extends beyond property lines. You may be liable for both
controlled and uncontrolled releases of collected runoff onto down
slope neighboring properties.
Don’t stay in your home if it becomes unsafe. Develop a
home- and neighborhood- evacuation plan. Stockpile emergency
supplies, including sandbags, a supply of sand, straw, etc. Pay
close attention to weather forecasts, flash-flood and storm
warnings, water levels in nearby creeks, etc. Evacuation plans
should always include at least one alternative escape route and a
list of important and emergency numbers, including numbers for
neighbors.
Get professional help with design and installation of any temporary
or permanent measures to control runoff and prevent an erosion
problem.
What to
watch for
Roadway-related problems, flooding, existing
gullies, and eroded areas, including stream-bank erosion are likely
to appear or get worse the first winter after a fire. Sediment
levels in creeks and waterways are expected to rise, reducing
channel capacities and increasing the likelihood of flooding.
Note: If flooding or
mudslides occur and impact road surfaces, do not attempt to drive
over flowing water or mud.
Some signs of impending danger from debris
flows, landslides, severe erosion, or imminent flooding include an
intense storm event (one- to two-inches per hour), previous rainfall
that caused ground saturation, water flowing over the landscape
where it hadn’t appeared in previous winters, leaning or falling
trees, and tension cracks. Watch for seeps and increased spring
runoff on slopes, like severely disturbed and unprotected slope
areas caused by firefighting effort or from recent activities to
remove fire damaged trees and other slope-holding vegetation.
For more about fire-hazards, retardants,
erosion-control, plant lists, and other natural-resource information
for your property, visit the Resource Conservation District of Santa
Cruz County at www.rcdsantacruz.org, or call 831-464-2950. You can
also call the USDA Natural Resources Conservation Service at
831-475-1967.
The Natural Resources Conservation Service is a
federal non-regulatory agency under the United States Department of
Agriculture. All services are available free of charge, through a
mutual agreement with the Resource Conservation District of Santa
Cruz County.
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