FLOODING, LANDSLIDES, AND THE DROUGHT— WHAT ALL THIS RAINFALL MEANS FOR SOUTHERN CALIFORNIANS.
Earlier this week, the all too familiar buzzing of the emergency alert system could be heard coming from three separate phones vibrating in our home. Craning my neck to read the nearest screen, I made out the warning, “ALERT!! Flash flood warning for Thomas Fire burn areas and Santa Barbara County, seek high ground”. When it comes to flooding, our house, which sits midway up a large hill that burned in the Thomas Fire, will likely avoid flooding. However, the neighbors whose homes are located towards the bottom of the hill have lined their driveways and porches with sandbags to prevent the rushing water from entering their homes. There are of course other concerns that come with living so close to the recently charred mountains, landslides and damage from debris flow being some of the most prominent.
As 80 miles-per-hour winds rip through Ventura and Los Angeles counties, residents have been encouraged to stay off of the roads and out of high debris flow areas. This downpour marks the second in a string of powerful storms making their way across California, flooding roads, loosening hillsides, and prompting evacuations in wildfire burn areas where the intensity of rain could inflict devastating damage.
The Thomas Fire, which burned throughout Ventura and Santa Barbara in December 2017, is not Southern California’s most recent fire but the effects of weakened hillsides and burned vegetation from the wildfire are still being felt by residents who live near burn areas.
Why does it take such a long time for the hills to recover after a fire?
During large wildfires like the Thomas Fire and the more recent Woolsey fire, vegetation and their vital root structures responsible for water absorption during a rain event are destroyed. As vegetation burns, the soil found just below the plant’s mineral line begins to repel water after being exposed to high-intensity heat. This impermeable layer of dirt, known as the hydrophobic layer, is formed when a waxy substance released by the plant during fire eventually cools and hardens in the soil, making it very difficult for water to move from the surface to deeper layers. Since rainwater cannot be easily absorbed by the soil, flooding and debris flow become more common. According to Ventura County’s emergency information, “it takes an average of 3-5 years for vegetation to re-establish itself to a point where water absorption and soil stabilization returns to the pre-burn condition”.
How does all of this rainfall impact the drought?
The Ventura River has some of the highest waters levels that locals have seen in a while and is currently overflowing its banks (see video above). When it comes to the drought, flooded roads and filled reservoirs do not necessarily mean that California is in the clear. According to the state’s Department of Water Resources, though the severity of the drought has decreased because of the recent rains, the need to conserve water is still very real. After nearly ten years of record low-water levels, it is going to take time and a lot more rainfall for the state to fully recover.
Earlier this month, it was reported that seven of the state’s 12 main reservoirs have been filled to at least 98 percent of their historical average. Still, many of the areas that experienced severe drought warnings, most notably those in San Bernadino County, will not get a break from the imposed water restrictions until California experiences several years worth of abundant rain.
Farmers, who according to the Public Policy Institue of California are responsible for approximately 40% of California water consumption, are rejoicing in the rainfall because it means lower water bills and free irrigation during the storms. As someone who splits their time between wilderness education and working on a small farm, I can report that the farmers that I know are thrilled to be receiving so much rain in 2019!
Understanding why mudslides, landslides, and debris flow occurs helps people living in burn areas understand and prepare for natural events that might disrupt or destroy their habitats. HWF encourages you to look beyond the flooded streets and seemingly abundant water to the hot summer when water will not be as readily available. Shorten your showers, turn off the tap when you brush your teeth, and help conserve water whenever you can. It is one of our Earth’s most precious resources!