Protecting scorched yards from rains

Now that homeowners in wildfire zones are returning to their properties, a new battle begins: protecting their precious topsoil as the winter rains arrive.

The likelihood of runoff and erosion doubles after fires in urbanized areas because recently scorched soils become hydrophobic, meaning they repel water.

Fires cook the waxes that are natural to our soils. When these waxes cool, they coat the first inch of soil with a repellent layer, stopping water from infiltrating.

So when the rains come, instead of soaking into the ground, the water streams over the top, jamming stormwater drainage systems with mud and debris and sending torrents of runoff into yards, streets and even homes.

Resist the urge to dump mulch on the property, however. It won’t stop erosion, but it will stifle the new growth of weeds and other seeds that are crucial to holding the damaged soil in place.

We need to hold our ground, so try to shrug off the fire fatigue and do these six things as soon as you can:

Dampen your soil: A little sprinkle can help break the “repellent” layer. This first watering should be super light — use a fine spray. Once the soil starts absorbing those little showers, begin deeper waterings. The goal is to encourage seeds, roots and surviving plants to sprout.

Break out the hoes: Grass rakes, hoes, even Hula-Ho weeders can be lightly dragged across the top of the soil to break up the barrier.

Clear drainage systems immediately: Water pouring out of culverts, gutters or drains is a leading cause of erosion.

Dig a ditch or fill a sandbag: Driveways, roadways, sidewalks and parking lots are often designed to “sheet” their water runoff into landscaped areas, but after a fire, those soils won’t be able to handle the load. Instead, use sandbags, diversion ditches (a.k.a. swales) or other materials to divert runoff from hardscape areas.

Tread lightly — or not at all: Activity on flat ground can compact the soil and lower its water absorption rates, which further destabilizes the soils on slopes.

Leave the mess for now: The charred remnants of plants and whatever else the fire left behind protect against erosion. Postpone cleanup until you’re ready to begin restoration.

home@latime.com Kent is the author of “Firescaping: Creating Fire-Resistant Landscapes, Gardens, and Properties in California’s Diverse Environments.”