California flooded: How to combat the threat of mudslides

SAN DIEGO (AP) — Relentless storms from a series of atmospheric rivers have saturated the steep mountains and bald hillsides scarred from wildfires along much of California’s long coastline, causing hundreds of landslides this month.

The debris has so far mainly blocked roads and highways, but has not caused any harm to communities. in 2018 when mudslides roared through Montecito23 people were killed and 130 homes destroyed.

However, more rain is forecast, which increases the risk.

Experts claim that California has learned many lessons from Montecito. There are more tools available to locate hot spots and there are more basins, nets, and other devices to catch the debris before it reaches the homes. As climate change causes more severe weather, the recent storms will put these efforts to the ultimate test.

WHY IS CALIFORNIA PRONE to MUDSLIDES?

California’s mountain ranges are young, from a geology standpoint. It is covered with loose rocks and soil, which can be easily slopped off, especially when it is wet.

Nearly all of the state received rainfall totals that were 400% to 600% higher than average since Christmas. Some areas saw as much as 30 inches of precipitation. This has caused massive flooding. Since December, at least 19 people have been killed by severe weather.

Since New Year’s Eve, the California Department of Conservation’s landslide mapping team More than 300 landslides have been documented.

Things are worsened by the state’s long-lasting drought.

Dan Shugar, an associate professor of Geoscience at the University of Calgary said that drought can have a counterintuitive impact when it is combined with the extraordinary rainfall California has experienced in recent days.

“You’d think if the ground is dry it should be able to absorb a lot of water, but when ground becomes too dry, the permeability of the ground actually decreases,” he said. Water can carry soil and debris away by moving down from the soil that has been hardened.

Wildfires have also left some hillsides without any vegetation to keep the soil in place.

WHAT ARE THE MOST VULNERABLE AREAS?

The most vulnerable areas are hillsides that have burned in the past two to three years with communities below them, said Jeremy Lancaster, who leads the California Department of Conservation’s geological and landslide mapping team.

He added that the area includes those areas that have been burned in Napa and Mariposa counties.

The deadly mudslides that struck Montecito in 2018 occurred about one month after the worst fires of California history, which charred 280,000 acres.

Montecito lies between the Santa Ynez Mountains and the Pacific Coast. The community was evacuated on Jan. 9, five years after the tragedy.

Lancaster warned that the danger of landslides would persist long after the rains subside as water seeps 50 to100 feet beneath the soil. This can cause damage and even lead to the destruction of property.

“They can occur weeks later, if not months,” he said.

WHAT CAN YOU DO TO PROTECT COMMUNITIES

Lancaster claimed that California has made a significant increase in its efforts to find hotspots following the Montecito mudslides. His department constantly updates its map to ensure that communities in the area are informed and can make decisions about whether or not to evacuate a whole community.

The state is also developing a system that can pinpoint when rain could trigger a landslide.

Marten Geertsema, who studies natural hazards and terrain analysis at the University of Northern British Columbia, said agencies use a variety of tools to gauge the likelihood of landslides in a given area, including terrain maps and lidar – pulsed light from lasers to penetrate foliage to see the ground. They can then monitor for early warning signs, such as changes in photos from the air or satellites or data from GPS monitoring stations and tilt meters.

WHAT IS THE MOST EFFECTIVE DEFENSE AGAINST MOODLIDES?

One of the best ways to manage landslides is with debris basins – pits carved out of the landscape to catch material flowing downhill.

Experts say that basins that require large amounts of land can disrupt the natural ecosystem. They can lead to beaches being flooded by sediment from the canyons.

They can also be very costly, according to Douglas Jerolmack, an assistant professor of mechanical engineering and environmental science at the University of Pennsylvania. And if old debris isn’t removed, they can be overwhelmed by new landslides or mudslides.

Jerolmack stated that some might not be large enough to handle future slide worsened due to climate change.

After the 2018 mudslides hit Montecito, the Los Angeles Times reported that debris basins above the community were undersized and hadn’t been sufficiently emptied.

Patrick McElroy, a former Santa Barbara fire chief, who founded The Project for Resilient Communities, stated that the tragedy galvanized the community and raised millions of dollars to address the problem.

The company hired an engineering firm to map the canyons. They also installed debris nets. According to him, the recent storms had put them to the test. One net measuring 25ft tall was nearly full.

McElroy stated that he is still haunted from the 2018 memories, but feels better knowing that the community may be safer.

“I’m not over it yet. It was amazing to see no injuries or fatalities when I woke up the next day. I just can’t tell you how impressed I am,” he said of the nets.

According to Larry Gurrola (an engineering geologist), the best solution for Santa Barbara and Montecito is to have both debris basins and nets.

However, nothing is free. Santa Barbara County spent $20 million to build a new basin in 2018, while McElroy spent nearly $2 million to install the nets. This includes liability insurance, and other fees. The permit is valid for five years and will expire if not renewed.

Gurrola stated that the alternative is more expensive. With the recent storms, more than half of California’s 58 counties have been declared disaster areas and repairing the damage may cost more than $1 billion.

“Most importantly these things protect the community and save lives,” he said.

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Glass reported from Minneapolis.