Natural Hazards in Silicon Valley

Natural hazards collage - natural hazard zones to considerWhat are the natural hazards in the San Francisco Bay Area and Silicon Valley?

The main natural hazards to consider are:

  • earthquakes
  • floods
    • 100 or 500 year flood plains
    • floods from dam failure or levee failure (includes rising sea and bay water levels)
  • liquefaction zones (and compressible soils areas)
  • landslide zones
  • fire risk areas, such as the Very High Fire Hazard Severity Zone
  • for those with basements (few homes), radon

There are zones associated with these potential risks and those areas are delineated by the state, county, and local jurisdictions. The state level earthquake faults are those which are considered active in relatively recent years. The county mapped fault zones may not have been active in over 10,000 years and the town or city labelled areas have been dormant for much longer than that.

Where to learn about natural hazards and natural hazard zones in Santa Clara or San Mateo Counties:

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Are Fire Seasons New?

Fire season is a concern for all on the West CoastFire season is a concept we are familiar with in the West Coast, but it may be foreign to those moving here or living far away.

Not long ago I was on the phone with a cousin from the East Coast. That area had recently been hit by Tropical Storm Ida and over here we were being smothered by the smoke from the Northern California fires (Caldor, Dixie, Tamarack and some others). Aghast at enormity of it all, my cousin asked the poignant question, “has there always been a fire season, or is that a recent thing?”

Fire Season

Briefly, yes, California has always had a fire season.

One major reason people (myself included) love California is for its mostly dry Mediterranean, subtropical climate. However, that ideal dry hot summer climate is also a perfect tinderbox. Without summer rain, the grasses and annuals die off and many native perennials go dormant. Dry hot winds, frequent from around August through October, dry out the landscape even more. By this time, an open hillside is A-grade kindling – one little spark and it’s a recipe for disaster.

Even in wet seasons with no drought, the summer will always be hot and dry with a high risk of ignition. So while fire season is nothing new, it’s longer and much worse than it used to be.

Fire and California Homes

For California homeowners and buyers, the increasing fire danger is strongly felt. Most buyers tell me they do not want to be in high fire risk zones, but might not always know what to avoid. State and local governments have put more preventative regulations in place to keep homes safe from wildfire, both on builders and homeowners.

If you are relocating to Silicon Valley, you may be wondering what the risks of wildfire are like for this area. There are plenty of resources available online, and I always recommend clients to look at the hazard maps such as those listed in my article Tools You Can Use When Relocating to the San Jose Area. While the mountain and foothill communities may be at risk of wildfire, even the lowlands are experiencing another concern that comes with harsher fire seasons: smoke and air quality.

In my other blogs I have more articles dedicated to the topic, so I won’t go into detail here. I encourage you to view some of my articles about Fire at the Live In Los Gatos Blog or over at the Valley of Heart’s Delight blog under the Natural Hazards and Safety categories if you’re interested in learning more.

Some of the oldest trees living in California have the scars of past fires, sometimes multiple. Native plants have evolved and adapted to fire and can thrive in its shadow. And for as long as people have lived here, they have contended with seasonal fire danger.

Fire season 2021 has come to an end with the arrival of rain – a double bounty since we are in the middle of a severe drought. When the rains come, the problems aren’t over, though. In burned out areas, the next challenge will be mudslides and further damage to the fire zones. This is an old problem also, I remember hearing about the mudslides following the fires as a kid growing up in the 60s and 70s.

Fire hardening” is an important concept for those of us who live in or near large open spaces with hills especially. I suspect it will grow into a cottage industry with new experts appearing to advise or possibly install features which will make our homes and landscaping more resistant to advancing flames.

Tools You Can Use When Relocating to the San Jose Area

If you’re relocating to the San Jose area, there are a few tools you can use for resources as you evaluate different parts of the region. When I started this website, I had books listed that you could purchase. Today, mostly I have websites that you should bookmark – for free!

Natural & Environmental Hazard Information Tools You Can Use

Natural hazards are found throughout the United States, often the major one people consider is the one hundred year flood plain. Here in the Golden State, we have some additional concerns relating to fire and earthquake risks.

  • California MyHazards can display a map anywhere in the state with information relating to liquefaction zones, earthquake faults, 100 year flood plains, and high fire risk areas.
  • Flooding from Dam Failure (potentially caused by earthquakes as well as other possibilities) is scary. Learn more about those zones at the link I’m providing here. (As of this writing, the Approved Inundation Maps link is not working.)
  • A Barclay’s Locaide will outline earthquake faults, flood plains, and other natural hazard zones you might want to know about. This is now out of date, but you may be able to locate a used one online or see if a local real estate association of Realtors bookstore has it available. 
  • Earthquake Zones of Required Investigation can be used throughout the state to identify landslide, liquefaction, and other zones relating to quakes.
  • Something else to know is that there are state mapped earthquake faults (the more active ones, such as the Hayward or San Andreas Fault) and also the city, town or county mapped fault zones (for example, the Shannon Fault). The latter may have been dormant for 11,000 years or more.
  • Buying a home? Sellers usually provide a Natural Hazard Report, an Environmental Hazard Report, and a Tax Report from a company such as JCP. This same company / site has a great amount of information on local conditions on its About the Hazards page that newcomers would benefit from.
  • When buying a home in California, consumers are given a link to download brochures, or one combined document, on a variety of hazards. I’m not sure that most of them take the time to read it, but it’s excellent info and I highly encourage anyone living in CA, whether renting or owning, to read it:
    Homeowner’s Guide to Earthquake Safety & Environmental Hazards

Environmental Hazard Zones

  • Local concerns also include environmental ones, such as SuperFund sites. here you can see SuperFund sites in reuse (meaning offices and homes on those sites).
  • Some sites with spills, leaking underground storage tanks, or other issues can be found at this Cleanups in my community page (nationwide info)
  • Mercury, or quicksilver, was mined in Almaden (New Almaden and related mines) and east Los Gatos (Guadalupe Mine area) – it is a naturally occurring element in cinnabar. For that reason, creeks in those areas should not be entered or fished in.
  • Asbestos is another naturally occurring element here. It was prized for being somewhat fire resistant and was mined under Communications Hill. It’s something to investigate if you want to live in that area.
  • Oil, gold silver, and other elements were mined here as well as granite (we still have quarries active in Santa Clara County today, a couple in the Cupertino area and one in the hills by Lexington Reservoir just outside of Los Gatos). Some old mines are not mapped if they are on private land, so one of the disclosures we have relates to unmapped, abandoned mines., which may be found in more rural pockets of the county.

Other Priorities for the Tools You Can Use list

In addition to natural and environmental hazards, there are big plusses that will attract new residents.

It is also helpful to have a knowledgeable Realtor as your resource!  Please call me if you’d like assistance in your move to SIlicon Valley. I’d be happy to help you.

 

Related Reading

Silicon Valley liquefaction zones (on the Valley of Heart’s Delight blog)

Is there a radon risk in Silicon Valley homes? (Valley of Heart’s Delight blog)