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 donít 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.

Donít 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 hadnít 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.

 

(c) 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009 mountain network news All rights reserved.