Stephen Caruana
The Cocos Fire one month after the 2014 blaze. The May outbreak …
Erosion control best practices
There are various ways to stabilize slopes in a post-fire scenario, each guided by the expected severity of downstream effects from failure. A thousand acres of untreated severely burned steep canyon could cause massive erosion that gathers in the canyon below.
The most common mitigation technique for slopes of more than 20% grade is hydromulching. However, not all hydromulch is the same.
Some mixtures are designed for rangeland applications and may contain non-native materials that aren’t appropriate for forest or wild land slope restoration. Every combination of water, fiber (wood, paper), and tackifier (adhesive) is rated for an expected life from three months to two years. Many fire-prone communities recommend or certify specific seed mixtures that have been tested in certain areas.
Another option is to place straw or grass wattles, or loosely spread rice- or weed-free wheat straw, to keep non-native grasses and weeds from colonizing treatment areas over bare and distributed soil. The wattles are placed in rows with overlapping joints, much like you’d build a brick wall. Some excavation may be necessary to ensure they’re packed tightly against one another, making this option more expensive.
Straw bales are not an industry best practice for fire erosion control. While they’re readily available and biodegradable, they require a great deal of maintenance, are impermeable, and cannot withstand high flows common to mudslides and landslides. They should be used only as a temporary measure.
Another practice is to use contoured log terraces but these also have limited applications. Burned logs in heavy timber areas can provide a barrier to runoff and direct water away from high-risk areas. These dead trees can be felled, limbed, and placed parallel on the contour perpendicular to the slope’s direction. Water meanders back and forth between the logs, reducing velocity and gives water time to percolate into the soil.
In summary, post-fire erosion control solutions should only be performed under the guidance of a contractor or consultant certified in sediment and erosion control by organizations such as EnviroCert International Inc.
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