The arrival of Hurricane Hilary, though downgraded to a tropical storm, an extremely rare weather event for Los Angeles County. And with the landfall of a tropical storm, we’re expecting heavy rain and winds.

The heavy rains expected from Hillary will be similar to those of an extremely heavy wintertime, and such storms can result in significant erosion, causing mudslides, leaving hillsides particularly vulnerable. So what should people in Los Angeles County expect from the rain?

What should people expect?

According to Ryen Kittell, a meteorologist with the National Weather Service, given Hurricane Hilary’s unprecedented nature, there is some uncertainty as what to will occur. 

The LA metro area is expected to see anywhere from two to four inches of rain, while in the foothills, rainfall in excess of six inches is possible.

For example in 2010, a severe winter storm produced such heavy rains, that the rainfall removed slit from underneath a road surface, causing a depression 35 feet wide and 10 feet deep in Los Angeles.

More recently, just this past winter, heavy storms caused powerful mudslides in La Cañada — a city at the foothills of the Verdugo Mountains — damaging multiple homes.

However, Kittell emphasized that we shouldn’t expect catastrophic mudslides in areas that don’t typically see them, even in the wintertime.

The event of a mudslide is directly related to heightened risks of flooding and road damage, which is why the National Weather Service has also issued a flood watch out for Southern California.

What areas are of most concern?

Hurricane Hilary, which will hit areas around Long Beach and the Catalina Island near Avalon particularly hard, is also expected to cause moderate erosion along the coast, swallowing up at least several feet of beach area that may impact nearby residences and other structures, though Kittell says that the occurrence of such a threat, though present, is still quite low. 

Areas that have a history of experiencing land movement are also particularly vulnerable to storms like Hurricane Hilary, according to Esteban Garcia, Associate Communications Depty for LA County Supervisor Janice Hahn, who represents the fourth district of LA County, which stretches from Palos Verdes to Long Beach.

Garcia gave the example of Rolling Hills Estates, where just last month, 10 houses were destroyed due to a landslide.

What has LA County done to prepare?

Kittell said that in the event of mudslides and other results of significant erosion, there is only so much that county officials can do with regards to preventative measures: some areas are just geographically going to be more vulnerable to heavy rains.

That being said, LA County officials have taken some steps to minimize the impact of Hurricane Hilary, internally and externally in coordination with the National Weather Service in unified commands that Garcia says are especially important to protect vulnerable areas.

LA County has also increased the number of operators available, especially at Public Works, to receive 211 referrals, which Garcia encourages residents to call if they see a fallen tree, a fallen power line, or other hazards, especially as the County works to make sure roads can remain open.

Garcia says the County has also handed out thousands of free sandbags, to help keep homes and other structures safe from flash floods and rising water levels in their neighborhoods.

In places like Rolling Hills Estates which has been subject to land movement before and is now especially vulnerable to another catastrophic event due to Hurricane Hilary, Garcia says the Department of Public Works has been monitoring the area continuously for additional movement.

Looking to the future, Garcia says that there has been more initiative taken to address stormwater capture and create clean water projects.

“There are two that are already under construction in our district, in Walnut Park and in South Whittier,” Garcia said. “So we hope that in the future, unfortunately as we face more extreme weather, that we will be better prepared to make that we’re able to capture [stormwater] but also keep it from accumulating in our neighborhoods.”

What should you do?

Garcia urges residents to contact their own local public works departments for any specific questions they may have about how their neighborhoods may be impacted by the hurricane. He also says it’s important that residents sign up for alerts, so that they can stay in the know of the storm will affect their area and for future major weather events.

Garcia also says it’s important to take advantage of the Department of Public Works’s road closures website, which is updated with which roads are going to be open and safe to use during the hurricane.

Adding to that, Kittell said that the National Weather Service is especially worried about flooding to and from the desert, particularly going through the I-5 corridor towards Las Vegas. “Any of that travel, really avoid it in the Sunday Monday time period,” he said.

For more information on Hurricane Hilary, check with the National Weather Service on their website or with the LA office’s Twitter account.

Amber X. Chen is a freelance journalist from Southern California whose work focuses on environmental justice.