Soil and water

Scorched Earth and Soil Rx

By Tery Susman, UC Master Gardener of Mariposa County.

MARIPOSE — Forest fires can create immediate and potentially long-term soil erosion. However, there are several ways to alleviate this problem after a fire.

The following was adapted from the California Native Plant Society’s fire recovery guide.

1. Leave the mess; keep it safe.

Soil protection, if necessary, is provided by what the fire has left behind. Ashes, debris, heat-damaged fallen leaves, and charred remains of plants can protect the land from wind and water erosion.

Image of a wheelbarrow filled with mulch.

Image by Manfred Richter.

If a fire has burned so badly that no material remains on the ground, patches of soil crust over and become hydroponic (water repellent), increasing runoff. This may require the application of shavings, mulch of dead debris or straw.

Mulching is the most effective erosion control treatment because it provides what fire and heavy equipment have taken away: ground cover! This ground cover allows water to seep into the soil instead of running off and eroding it.

Prune or remove only high-risk fire-damaged trees near buildings and roads. Keep trees felled and pruning in place. These trees can be a source of mulch.

Image of water flowing down a hill after a forest fire.

Image by Maxwell Rygiol-Detwiler.

2. Minimize soil compaction.

Keep foot traffic and equipment off the burned landscape. Activity on slopes increases erosion, weakens soil bonds, dislodges soil particles, and tramples newly sprouted plants. Activity on flat ground can compact the soil and reduce its rate of water absorption, which increases runoff.

3. Successful Strategies

Spread: A mulch application. Straw mulch is highly effective in reducing rainwater runoff, soil erosion and downstream sedimentation. Use loose barley or wheat straw as it lasts longer. Rice straw is cheaper. Use when the straw doesn’t need to last that long. Use loose-form straw mulch, no deeper than 2 to 3 inches. Mulch in 6 to 10 foot strips along the contour, spaced 50 to 100 feet apart, depending on the steepness of the slope.

Use wood mulch from local materials, including burned trees, shredded debris, or thinned, unburned trees, wattlesmulch, rocks and branches can slow and disperse runoff, limiting erosion and sediment.

Use straw wattles to shorten the length of the slope. They are designed for short slopes or slopes flatter than 3:1 and low surface flows.

Image of a bulldozer in front of piles of gravel.

Gravel and crushed rocks work very well to limit erosion.

Sink: Place stones, gravel or crushed rock in high traffic areas.

To share: Work with neighbors to create a plan to slow runoff. In disturbed areas with moderate to high fire intensity, a neighborhood plan may be essential to prevent sediment and fire debris from entering sensitive stream habitats and contributing to flooding.

4. Ask for advice: Many professionals are available to intervene in the event of a claim on site. If you are concerned that your property may be threatened by flooding or a debris flow, contact these organizations:

Natural Resource Conservation Services: Visit them at or call 209-966-3431.

Image of the CAL FIRE logo.Fire CAL: Visit them at or call 209-966-3622.

Recovering from a wildfire can be a daunting process. Be patient with yourself and with nature. Do what you can, ask for help, and know that our community is STRONG!

Next: Give trees a chance – Resilience of ecosystems

About UC Mariposa County Master Gardeners

The Mariposa County UC Master Gardeners are located at 5009 Fairgrounds Road, Mariposa. For more information on gardening and events, visit their website Where Facebook page (UC Master Gardeners of Mariposa County).

UC Master Gardeners has a hotline serving Mariposa County, including Greeley Hill, Coulterville, and Lake Don Pedro. Please contact them at 209-966-7078 or by e-mail at [email protected].

Listen to them on the radio at KRYZ 98.5 FM Wednesday at 2 p.m. and Saturday at 5 p.m.

Watch this short video on how to manage water drainage on your property!