An updated map of Montecito, Summerland and Carpinteria areas that are at risk of debris flow or flooding this storm season were released Thursday by Santa Barbara County officials.
The new risk map, dubbed the “Interactive Storm Impact Consideration Map,” is available on the county’s website here.
It includes up-to-date scientific research and data gathered after the 2017 Thomas Fire and debris flows on Jan. 9, 2018.
The number of parcels on the map considered to be at risk from potential flooding and debris flows dropped significantly compared to previous maps.
The number of affected parcels is now 517 compared to nearly 1,500 properties last storm season.
Areas identified as “storm impact parcels” and “storm impact zones” are shown in red on the county map.
Several affected neighborhoods are along creeks.
“We are still at risk, but the level of risk is substantially diminished from previous years,” Kevin Taylor, fire chief of the Montecito Fire Protection District, told Noozhawk. “While we remain at risk for debris flows, our highest-risk or more likely event is flooding.”
Taylor and other emergency leaders spoke at a community meeting in front of more than 100 people at Montecito Union School.
There was more good news Thursday for communities below the Thomas Fire burn area.
There is less rock and other material in the canyons that could be carried downhill by heavy runoff because watersheds are restored, but more time is needed for vegetation to completely grow back.
Vegetative recovery after the wildfire and mitigation measures such as steel cable debris-catching nets, empty debris basins, and clear waterways have reduced the threat of debris flows.
An average of about 80 percent of the watershed in the charred areas grew back in the mountains, according to Kevin Cooper, a scientist with the federal Burned Area Emergency Response team.
“That will go a long way to slow down the possibility of a debris flow,” Cooper said. “It (the watershed) is not back to where it was before the fire, and the soil itself has a way to go before it’s recovered all together.”
The Thomas Fire burn area is vulnerable to debris flows for three to five years after the blaze, Taylor told the crowd.
“We are in the middle of that 3 to 5 year risk period,” Taylor said. “For all these reasons, it’s appropriate that we, as a community, change how we respond to this new risk.”
A Light Detection and Ranging (LIDAR) device detailed the topography, and the technology was used as the foundation of the new map.
Local emergency managers will use the map to determine what portions of the community will be evacuated if needed.
Over the last two years, emergency officials ordered evacuations based on rainfall intensity and duration, and the threshold for this winter has changed because there was some vegetation regrowth on the watersheds burned in the Thomas Fire and other efforts.
Authorities had previously ordered evacuations if the forecast was greater than 0.8 inches of rain per hour for the Thomas Fire burn area on the South Coast.
That occurred three times last storm season, and areas have exceeded an inch of rain per hour for the Thomas Fire burn scar during two storms, Taylor said. Localized flooding happened, but Montecito did not experience debris flows.
Evacuation orders will now be issued if a “saturation rainfall event” is followed by a high-intensity and short-duration rainfall during storms.
The National Weather Service defines a “saturation rainfall event as “approximately 10 inches of rain in 2 to 3 days,” Taylor said.
“The scientists we have been in consultation with this summer and fall tell us that during this transition period, our greatest risk is during a saturation rainfall event, not a single high intensity, short-duration rainfall event,” Taylor said.
The information is based on the 1969 floods in Montecito, historical records and a study of damaging flooding and debris flows after the Coyote Fire in 1964.
A “Storm Impact Consideration Team” will examine several factors before issuing evacuations this rainy season for the Thomas Fire burn area.
Authorities will determine rainfall quantity and duration, how much precipitation the burn scar received, and in what time period. Officials also will consider the status of watersheds and how the watersheds are handling the rainfall.
“This year, judging by the creek channels during two storms, the watershed appears to be absorbing the majority of the moisture,” Taylor said. “So far this storm season, we have received more than three inches in most areas above Montecito.”
In addition, officials will tell people to leave the area after considering the status of debris-control nets, debris basin capacity and creek channels.
“No two storm events are the same, and the watershed responds differently to each,” Taylor said. “Flood control and the Fire Department will be closely monitoring impacts throughout this storm season to ensure that we have the most up-to-date situational awareness to make the best decisions possible.”
Emergency officials do not anticipate issuing protective action orders as the result of a single storm event because the highest risk is at the tail end of a saturation event, Taylor explained.
“Based on the long-term weather forecast for this winter … the weather service is telling us it’s unlikely we will experience any saturation storms, but that is just the forecast,” Taylor said.
Flash Flood Warning
History has shown Montecito is prone to flooding, and precipitation could be severe enough to trigger flooding even without the recent wildfires, according to Jon Frye, engineering manager for the Santa Barbara County Flood Control & Water Conservation District.
The weather service will issue flash flood warnings if actual rainfall is exceeding an inch of rain per hour, Taylor said. The NWS is relying on the Wireless Emergency Alerts system to notify residents if a flash flood warning occurs, Taylor explained.
People should move to higher ground if safe to do so during a flash flood warning.
“The appropriate protective action in this case, if your property is located in the red on the map, is to move to higher ground,” Taylor said, emphasizing public safety as the highest priority.
Decision-makers will issue emergency alerts if needed this storm season.
If a storm is forecasted that could cause a debris flow, the risk area will be evacuated, emergency officials said. In the event of a rapidly developing storm with little to no warning, people living in the risk areas should have a plan to protect themselves and their families if it’s not safe to evacuate.
“If we are getting near the saturation rainfall event criteria, and considering a protective action like an evacuation warning or order, we will notify you if you are located in the red area of the map,” Taylor said. “If we are under a flash flood warning, we and the NWS will communicate the move to higher ground protective action order.”
The January debris flows killed 23 people and destroyed or damaged hundreds of homes just weeks after the Thomas Fire burned most of the hillsides and mountains above Montecito.
Click here for a list of resources, including how to sign up for alerts and where to find city-specific emergency information.
Residents can register for Aware & Prepare emergency alerts from Santa Barbara County by visiting the ReadySBC.org website or AwareAndPrepare.org and click on the red button that states, “Register for Alerts”.
The debris flow risk maps for recent burn areas from the Cave Fire are available on the county’s emergency website, ReadySBC.org, in addition to winter storm preparedness materials.
Thursday’s meeting was broadcast live on the county’s YouTube channel.
Attendees also participated in a 30-minute question-and-answer session with officials at the gathering.