RichmondSFBlog reader Gideon directed me to a recent story in the Bay Citizen about the potential tsunami risk to San Francisco. We had one warning last year and another one ten days ago in the wake of the 9.0 earthquake off the coast of Japan; that warning closed Ocean Beach and the Great Highway for most of the day.
San Francisco’s coasts are no stranger to tsunami activity:
Fifty-one tsunamis have reportedly hit the San Francisco Bay since 1850; nine of them originated in Alaska, according to the San Francisco Emergency Response Plan. The most recent tsunami events in the Bay Area happened in 1946, 1960 and 1964, but there are no recorded deaths from tsunami-related events in San Francisco County.
The greatest risk to our part of town is along our coastline at Ocean and Baker beaches. The good news is that we’d have some time to prepare for a tsunami. According to the article, we’d have 4 to 5 hours to evacuate if a 9.0-magnitude earthquake struck Alaska’s Aleutian subduction zone.
In addition, state researchers have prepared “inundation maps” to pinpoint where the risk is the greatest, and help residents and city planners with emergency planning – deciding who and where to evacuate first. The inundation map below shows red areas where a tsunami could cause flooding problems on our coastlines and in the bay.
Only about 3 blocks along Ocean Beach put the Richmond District at risk (highlighted in yellow on the map). If a tsunami did hit, we’d also benefit from the La Playa condominiums on the Great Highway which would help dissipate some of a tsunami’s impact.
Ocean Beach is highest on the city’s list of tsunami hot spots, according to the city’s comprehensive 48-page tsunami plan (download here). According to the plan, the city’s at-risk area extends “from Sutro Heights Park on the North, to the San Francisco County Line on the South (Ocean Beach), running north to south and parallel from 46th Avenue to the San Francisco Zoo. At that point the inundation line moves east to include the Zoo grounds and Lake Merced. Approximately 45 blocks of the Sunset District and 3 blocks of the Richmond District are in the affected area.”
An inundation map showing red areas where a tsunami wave could cause flooding on our coast lines.
Courtesy of Bay Citizen
Ocean Beach and all beaches on the City’s western shore are top on the list of first response areas in the case of a tsunami threat. There’s also a siren system in place which was not activated last Friday as the Department of Emergency Management determined there was not enough risk. It’s the same siren you hear tested every Tuesday at noon. You can read the city’s 48 page tsunami plan here.
Read the full story at Bay Citizen
Sarah B.
Look for the signs in the west part of town. They indicate evacuation routes, and if you hear a siren other than Tuesday noon,heads up!
The La Playa condominiums would probably face the same fate as many wood structures in Japan if the tsunami was equal to theirs…they had 10 meter high concrete tsunami walls which were no match…the force of the wall of water would probably knock the condos down quite easily. The outer Richmond District neighborhoods gain altitude starting around 43rd Ave. I think the Sunset District would be more devestated further inland and certainly along the Great Highway. Other worries…can the lions and bears at the zoo swim?!
what about 5th ave? I believe I am about 200 feet above sea level but something tells me that still wouldn’t be high enough..
Hooray for the hills and cliffs of San Francisco! That said, I would not willingly stand on any of the cliff edges at Land’s End or over by Baker Beach if a tsunami ever did come in. One never knows how much force it would take to make some of them crumble. Yet last week there were tons of people standing there, just waiting for a photo opportunity. Some things just aren’t worth the risk.
i too am worried about the zoo animals, if such a disaster strikes our hood. i don’t know what kind of animal evacuation could be in place. there are many animals whose night quarters are made of heavy concrete which may be able to resist such a force, but there are many more who don’t have such shelters. let’s hope the crazy weather changes on our planet don’t bring us a tsunami or any other mother nature madness to any devestating degree.
@ Tyler, 200 feet is plenty. Staying above 30 feet is the general guideline. There was talk of 10-meter waves in Japan, and in Hawaii the warning was to stay above the 3rd floor if in a high-rise.
I suppose i feel safer seeing this map, being that I have Lincoln Park between me and the ocean…;)
There should actually be a large inflow at the zoo, as that was historically the marshy outflow from Lake Merced. I read somewhere that after 1906 earthquake the water level in Lake Merced dropped 6 feet and the outflow through the valley where the zoo now stands lasted two days and could be heard some distance away.
If water did breach whatever levees and sewer boxes “defend” the zoo, quite a bit of water would likely settle there (not to mention there’s not much of a natural drain for the Sunset District behind the Great Highway and its underlying box sewer;w whatever water lands there would stay a while).
The zoo is the second item on the list of priorities after Ocean Beach and all beaches on the western shore. Here’s what the 48 page plan says about the zoo specifics:
Zoo:
– Announce on the Public Address System the closure of the Zoo and evacuation route
– Secure the animals
– Clear all patrons from the zoo in an expeditious manner following designated routes of travel when leaving the zoo parking lots
– Request mutual aid assistance through the EOC
Sounds like in most cases, the animal habitats have some kind of secured area that would be relatively dry and protected for the animals.
Sarah B,
in regards tot he zoo i don’ think there is a sealed area for the bears at least. i have been behind the scenes there and if water did intrude the grottos, it may not bring down the structure, but i think it might flood the night quarters. i would be interested to hear how the zoo would keep the animals sealed in. the lion house is secure i think. although the grotto to the east end where the snow leopards live is not. the rhinos, hippo and primates would be in secure areas, but i dont know how the savannah structure or some of the hoof stock down south gate would fair. as well other assorted animals like the penguins, flamingos, childrens farm barn. as much as we don’t like the old concrete structures there, those might be the ones that stand up thru time.