Tsunami flood maps show Malibu coastline under water

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The Tsunami Inundation Map for Emergency Planning, Point Dume Quadrangle, which includes the beaches between Lechuza Point and Latigo Point.

Malibu Lagoon State Beach is seen most at risk for flooding during a tsunami. However, the chance of one occurring in Malibu is low.

By Olivia Damavandi / Assistant Editor

Prompted by the devastating 2004 tsunami that ravaged Indonesia and killed nearly 230,000 people in 11 countries, a new set of tsunami inundation maps for California’s coastal counties was recently released by USC, the California Geological Survey and the California Emergency Management Agency.

The maps are intended to help cities and counties in identifying their tsunami hazard and in emergency evacuation planning. Each map estimates maximum inundation levels brought on by the largest anticipated tsunami event. The maps do not, however, include any information about the probability of a tsunami affecting any area within a specific period of time, due to a lack of known occurrences in the historical record.

In 2005, tsunami warning signs were placed throughout Malibu, and other areas deemed at risk, and a pamphlet circulated that gave such advice as “run from, don’t surf a tsunami.”

Tsunamis are most commonly caused by earthquakes, but can also result from landslides or meteorites.

“Generally speaking and fortunately, the likelihood of tsunamis causing significant damage is low for Southern California,” Aggeliki Barberopoulou. manager of the USC Tsunami Research Center, said Monday in a phone interview. “We do not have accounts from local [tsunami] events for Malibu, but large distant events [earthquakes] in the Pacific Rim have caused damage on many parts of the coast of California.”

Tsunami inundation maps have been created for two areas within the City of Malibu: the Malibu Beach quadrangle, which includes the coastal stretch from Dan Blocker State Beach to Las Flores; and the Point Dume quadrangle, which includes the beaches between Lechuza Point and Latigo Point.

“The major concern for Malibu is not the frequency of events, which is low, but rather the large both residential and transient populations in close proximity to the coast,” Barberopoulou said. “The most vulnerable location in the city is Malibu Lagoon State Beach.”

Eighteen hypothetical worst-case scenarios were considered for the Malibu Beach and Point Dume quadrangles. The scenarios were developed through laborious computer simulations that calculate various details of each area.

Barberopoulou said waves could reach up to eight feet during a tsunami in Malibu. The highest waves are predicted east of Malibu toward Topanga.

Meticulous simulation is necessary because the effects from a tsunami are contingent on the orientation of the coastline (whether it faces probable earthquake zones); the form of the shoreline (which, in some cases, can make waves bigger by focusing them as they head to shore); and the local coastal landscape (hilly beaches are safer than those with flat topography).

“I believe that largely, the seismological community has been ignoring the threat from local tsunamis-mainly in Southern California-because the likelihood of such earthquakes is low, accounts or reports of local tsunamis are very scarce and most of the faults lying offshore Southern California are strike-slip faults (those faults where motion on each side of the fault is parallel to the fault),” Barberopoulou said.

“Ignoring a threat from potential sources because we do not have many accounts [of their occurrence] and because the likelihood of such earthquakes is low, is like assuming you are perfectly healthy without going to the doctor.”

Despite the small probability of a tsunami occurring, Barberopoulou stressed the importance of preparedness. Education and preparation are the best ways to avoid injury and increase one’s chances for survival in a tsunami, according to the California Geological Survey. It is recommended that residents find out whether they live in an inundation zone, and to learn evacuation plans provided by local governments.

Simply put, the best way to avoid a tsunami is to get to higher ground.

The inundation maps can be viewed online at www.conservation.ca.gov/cgs/geologic_hazards/Tsunami/Inundation_Maps/Pages/Statewide_Maps.aspx. More information about tsunami preparedness can be obtained online at www.pmel.noaa.gov/.