Foster Creek Conservation District
Gaining a Hold on Soil Loss Post Fire
Erosion by wind has removed 1.5 inches of soil, leaving bare roots.
The intense 2020 fire season will be felt for years to come in Douglas County. Fire effects soil stability in fields and slopes, wetlands and streams, mature wildlife habitat, and the spread of weeds. There are measures we can take to reduce erosion, which is the movement of soil particles by water and/or wind.
There are several ways that fire changes soils and their erosion ability. Soils can become more hydrophobic after fire, meaning infiltration decreases and more water stays on the soil surface. This leads to a greater chance of sediment runoff in fields and hillsides, especially during rainstorms, causing poor water quality. Sediment runoff also decreases crop production because there is a loss of topsoil and the ecosystem where the majority of micro-organisms live. Reduced and no-till farming practices have surface residue built-up to prevent such runoff, but fires can also burn this residue security blanket. Geologically hazardous areas on slopes and drainages are at an even greater risk of erosion after fires since vegetation that stabilizes the soils is gone. These fragile landscapes are already acknowledged by the Douglas County’s Voluntary Stewardship Program (VSP) as priority areas that are in need of stewardship practices to mitigate their erosion.
Fiber mat placed around a drainway to hold soils.
Assessing vulnerable areas around you and noting potential risks that may be associated with them will help you plan and prepare for future fires. For instance, if you live at the bottom of hill or downstream from an area that has burned, sediment movement and debris flows are more likely to affect you. Installing erosion control measures may help limit soil loss by wind and water during springs with rapid snowmelt.
Other tips to prevent soil loss:
- Mulching is a great way to decrease the effect of fire on landscapes. Mulch can be anything including straw, chaff, or even coir fiber matting that can be placed over more erodible areas like streambanks. It’s important to make sure your mulching material is weed-free. Weeds do not provide as much soil stability due to their shallow roots.
- Barriers are structures made of materials like sandbags, straw bales, log barriers, or silt fences that can be helpful on hillslopes to divert and slow water flows. These structures can also increase infiltration, as they can slow the water’s velocity down and create areas of pooling.
- Seeding and revegetation will likely be needed in many areas. It may be a bit late for this approach now; however, re-seeding in early spring will help. The best erosion control is grass seed as it grows quickly, is cost effect, and can easily cover a large area. Native species are best for habitat and wildlife benefits.
We thank the Washington State Department of Ecology for supporting this article.
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