Drought, wildfires steepen flood, mudslide risk

Fire and flood officials are warning that drought, wildfire scars and winter weather conditions have combined to increase the potential risks of flash flooding and mudslides in California this year.

Five years of drought have led to increasingly intense wildfires around the Bay Area and state. Those fires destroy the vegetation that is a natural erosion buffer and when storms hit burned areas, the likelihood of flooding and mudslides can increase dramatically, according to officials with the California Department of Water Resources and Cal Fire.

Drew Coe, Cal Fire’s forest practice program monitoring coordinator, said:

“It’s all about how much coverage does the soil still have. … If you see bare soil, the chances of your watersheds and hillsides for erosion is very much higher.”

The dangers increase as rain falls harder over shorter periods of time. A slow, steady storm that lasts a long time can be less dangerous than a storm that dumps a large amount of water over just a 15 minute-period, Coe said.

Coe was in Sacramento Monday with representatives from the Department of Water Resources and the National Weather Service to kick off the start of this year’s rainy season with an event highlighting the flash flood dangers associated with California’s fire season.

As of mid-October, the state had endured 6,726 fires that burned roughly 561,000 acres, according to the department.

Locally, people who live in and around the areas of the Loma Fire, which burned nearly 4,500 acres in Santa Clara County, and the Soberanes Fire, which burned more than 132,000 acres in Monterey County, should pay particularly close attention to weather forecasts this year, Coe said:

“The most critical thing is if you happen to be in a very high-risk area, it’s better to just get out and evacuate if there’s bad weather coming.”

Even in lower-risk areas, this time of year brings recurring challenges, said Tony Williams, spokesman for the Marin County Flood Control District.

Rising creek levels and so-called blue sky flooding torment residents every year, Williams said:

“It’s usually a sequence of several large storms or smaller storms that come back-to-back-to-back that contribute to rising creek levels.”

Blue-sky floods happen in the coastal areas during unusually large tidal events that bring massive amounts of water inland from the ocean.

People should pay close attention to posted warnings along roadways, never attempt to traverse water-covered roads, and stock up on sand bags if they live in low-lying areas prone to flooding, Williams said.

To help residents cope with this year’s wet weather, Marin County is hosting its second annual Flood Preparedness Fair on Saturday, from 10 a.m. to 12 p.m. at the Hilton Embassy Suites in San Rafael.