Los Angeles Tsunami Scenario

CaliNews — By L.A. Mama on December 19, 2011 at 4:36 pm

Tsunami preparedness information has been issued to residents of Los Angeles that live near the coast in the form of brochures and PDF files. These brochures/PDF files address the communities of Venice, West Los Angeles and the Harbor area of L.A., however the brochure also points out that “all low lying coastal areas” can be struck by a tsunami. Unfortunately, the brochure does not define at what elevation an area would be considered as low lying. There are color coded maps that show the areas of inundation for the city of Los Angeles, Los Angeles county and a small portion of adjoining cities/counties.

It is important for all residents of Los Angeles to be prepared for a tsunami if they spend any amount of time near the coast. A major aspect of being prepared is to know the warning signs of a tsunami.

WARNING SIGNS OF AN IMPENDING TSUNAMI

An earthquake
An unusual rapid receding of the ocean
Receding of the ocean/tide that seems unusually far so that it exposes the sea floor
Ocean tides that surge inland
A loud roaring coming from the ocean (some have said that it sounds like a freight train)

Tsunamis are caused by earthquakes, landslides, volcanic eruptions and meteor impacts, which are extremely rare. There are two types of tsunamis, local and Pacific-wide tsunamis. Local tsunamis can be caused by an earthquake near the coast or offshore and landslides. Pacific-wide tsunamis originate elsewhere. If Los Angeles were to have a local tsunami, the first wave could hit within 10 minutes, with little or no time for officials to issue a warning. That is why it is very important to know the warning signs of a tsunami and get to higher ground immediately. Pacific-wide tsunamis reach the coast of California within at least an hour, which gives ample time to issue a warning and evacuations.

Recent studies,cited by National Geographic, have shown that California is more prone to tsunamis than previously thought. According to Costas Synolakis, the director of Tsunami Research Center at the University of Southern California, “…even moderate earthquakes near the coast can generate large tsunamis by generating submarine landslides.” He also notes that this type of tsunami is capable of generating waves as high as 40 feet tall, which is similar to the waves that swallowed Japan on March 11th, 2011. CNN reported that some of these waves went 6 miles inland.

The inundation maps for Los Angeles included in the brochures/PDF files do not take into account the possibility of waves reaching 6 miles inland. Since much of L.A. is situated on slightly higher elevations than the areas noted in the brochure and maps, it is understandable that the waves wouldn’t reach many areas even on the coast. However, one thing that hasn’t been addressed is the fact that the Los Angeles River and Ballona Creek both lead to the ocean. My research (as noted below) indicates that these waterways, that are lined with concrete, could act as a channel for waves to surge throughout other parts of L.A.

Los Angeles County Coastal Monitoring Network : “Tsunamis can be amplified by bays, harbors, lagoons, or rivers and flood control channels, which can funnel the water and send it further inland. Stay away from rivers, flood control channels, harbors, marinas, and bays that can funnel the water from tsunamis”
National Oceanic and Atmospheric Administration: “Stay away from rivers and streams that lead to the ocean as you would stay away from the beach and ocean if there is a tsunami”
Red Cross: “Tsunamis can travel upstream in coastal estuaries and rivers, with damaging waves extending farther inland than the immediate coast”

The Los Angeles River (images below) twists and turns through Los Angeles and spans more than 51 miles. The following communities within Los Angeles, sit on the banks of the Los Angeles River:
*Canoga Park
* Reseda
* Van Nuys
* Sherman Oaks
* Studio City
* Universal City
* Toluca Lake
* Burbank
* Glendale
* Los Feliz
* Atwater Village
* Elysian Valley
* Glassell Park
* Cypress Park
* Chinatown
* Lincoln Heights
* Boyle Heights
* Vernon
* East Los Angeles
* South Central Los Angeles
* Maywood
* Commerce
* Bell
* Bell Gardens
* Cudahy
* South Gate
* Lynwood
* Paramount
* Compton
* Long Beach

Ballona Creek spans nine miles across the southwestern portion of L.A. through the neighborhoods of Culver City, Mar Vista, Del Rey, Marina Del Rey, Playa Vista and Baldwin Hills. It ends at Marina del Rey in the Santa Monica Bay portion of the Pacific Ocean. Below is a picture of Ballona Creek. On the left are the back yards of residents who live the community of Culver City, on the right is the lower portion of Mar Vista, showing Mar Vista Gardens. If you click on this picture to enlarge it, you will see the Pacific Ocean at the top.

The Los Angeles River and Ballona Creek were both lined in concrete and channelized after the Los Angeles Flood of 1938. After four days of rain fell on Los Angeles in February and March of 1938, 5601 homes were destroyed, 1500 homes were damaged, 115 people were killed and 800 cars were stranded. Although measures were taken in an effort to prevent flooding through channelization, these waterways flooded the city of Los Angeles again in 1969, 1980, 1983, 1992 and 1994 (read more about the Los Angeles Flood of 1938). Could a 40 ft wave traveling with great force and speed be funneled through these channelized waterways? If so, the loss of human life and devastation would be tremendous! Please take a moment to look at the photographs of the Los Angeles River and Ballona Creek above to judge for yourself as to how many lives would be in jeopardy (click on each to view larger). Los Angelenos need to prepare for this possible scenario. Go to ReadyLA.org to learn more about how to prepare for tsunamis, earthquakes and flash floods and build a disaster preparedness kit.

Sources:
CNN coverage of Japan Earthquake and Tsunami
City of Los Angeles Emergency Management Department Tsunami Brochure
Los Angeles County Coastal Monitoring Network: Safety Preparedness – Tsunami
L.A.Times: California Tsunami Could Come with No Warning
National Geographic Tsunami Facts: How They Form, Warning Signs and Safety Tips
Nationl Oceanic and Atmospheric Administration: Tsunami What Should You Do
Red Cross: Tsunamis
Suburban Emergency Management Project: Los Angeles Basin’s 1938 Catastrophic Flood Event