Dam Failure

When buying or selling a home in California, consumers can learn if the property is in a zone marked for potential flooding due to dam failure. The disclosure companies will not say which dam is causing the risk, or if it’s several since often there will be more than one dam along the same creek or river, as is the case along the Los Gatos Creek.

Quick take: you can learn about the areas which may be impacted by flooding due to dam failure at this link: Dam Breach Inundation Map Web Publisher.

Dam failure versus flood plain

To clarify, the 100 year flood plains and 500 year flood plains are different from the flooding due to a breach in a dam or levee.  If someone buys a financed home in a 100 year flood plain, the lender will require flood insurance.

Also relevant to the requirement for flood insurance: the 100 and 500 year flood plain inundation risks are considered to be “natural hazards” and the flooding from dam breaches are not, since humans have created the dams (or levees).  Per FEMA: “a flood resulting from changes in river flows is a natural hazard, whereas flooding due to a dam failure is considered a manmade hazard, and therefore excluded from the National Risk Index.”

Approximately 25% of floods in the U.S. are outside of the flood plains. It may be advisable for those in other areas to consider buying flood insurance even if it is not required by the lender.

Map of flood risk from dam failure

Recently Clair sleuthed out the State of California’s Dam Breach Inundation Map Web Publisher. This interesting and helpful tool is an interactive map covering both most counties and most dams. I encourage our readers to check it out.


Dam failure flood zones in Santa Clara County

Click on the image to view the live Dam Breach Inundation Map to better understand the risk of dam failure

This Dam Breach website indicates which dams have their flood risk from failure marked in one of four colors to indicate the higher or lower risk levels. In Santa Clara County there are more than a dozen dams marked at the highest risk category, and some of them hold a large capacity of water. (Some of the dams appear to not be at lake-like reservoirs, but more like covered percolation ponds or holding tanks.)

The concern today, of course, is what happens if we experience a large earthquake and any of these dams fail.

Lake Anderson in South County is the largest reservoir in Santa Clara County. It is undergoing a 10 year seismic retrofit and until it’s completed is at only 3% capacity for safety reasons.  You can view a short video about the retrofit here. With that in mind, take a look at the image below, which showcases what areas could be inundated should the dam there fail.

Dam failure flood zone with failure of main dam at Lake Anderson

Click to view the live map

The map doesn’t show if the flooding goes beyond the county line to the south, and unfortunately not every county appears to be participating in this website and not every reservoir is covered. I was curious about the enormous San Luis Reservoir just beyond our county’s border, but there was no map for that one.


Is Your Refrigerator Flooding?

Refrigerator with water dispenserRefrigerator floods are no laughing matter! Last month, my sister in-law’s fridge leaked causing the hardwood floors to pucker and swell, pushing cabinets and even lifting countertops! They’ve had to move out while their kitchen undergoes a massive overhaul. When my refrigerator line broke back in 2012, it was a similar story. The damage was extensive, and repairs were time consuming and expensive! So what can cause leaks and flooding and how can homeowners prevent it?

Causes for Refrigerator Floods and Leaks

Does your refrigerator have an automatic icemaker or a cold-water dispenser? If so, that plumbing is all capable of breaking. What if you don’t have a water line to your fridge? You can still have a leak. Humidity from the air and produce becomes ice or water when cooled. Modern refrigerators have been designed to automatically defrost: ice is melted, flows down a drain, and collects in a drip pan where it is heated (usually via waste heat from the refrigeration system) to evaporate the moisture. If the condensate is not taken care of properly it can become water damage!

Looking a little more closely, here are a few common causes:


Is your home ready for the heavy rains of an El Niño winter?

waterfallFor four years we have worried about the lack of rain and increased our conservation efforts.  Today lawns everywhere are dead, or hanging on by a thread.

Weather experts now say that there’s a 90% chance of an El Niño winter ahead.  Not only that, but they expect it to be a doozy.

My suspicion is that most of us are not really ready for all that water and the flooding that may ensue, so I wanted to suggest a little preparation for the rainy season (and the deepest hopes that it will refill our reservoirs and aquafers).   Here are a few suggestions from me, based on decades of attending home inspections:

  1. If it’s been more than 3 years since your roof was inspected, get a roof inspection done now, during the dry season. (Use a licensed roofing contractor to do it, not a handyman.) It’s better to do it before you discover a leak, and it’s better to do it before the roofers are booked out a few weeks!  The cost is probably going to be around $100 – $150.  Most homes need “tune up” work every few years, and that’s normal, so have the inspection understanding that some of your vent pipes may need resealing, a few shingles may need replacing, or other small items may require adjustment or repair.  If the roof is younger, that’s all it should be.  The old adage that “an ounce of prevention is worth a pound of cure” applies here.
  2. Make sure that the grading around your house or townhouse is correct and that the land slopes toward the yard & away from your home.  Grading is incorrect a lot of the time – I probably see my home inspector write that up more than half the time.  It matters because the water that comes down will follow the slope of the soil and you do not want it aimed at your structure.  You want the water to go away from your home.
  3. Your downspouts should direct the water away from the house, ideally 6′ or more.  This is super important, as the entire surface of your roof collects water and pushes it off through just a few openings, and in heavy rains this is a ton of water!  You do not want it lingering near your foundation because our clay soils are expansive when wet and that puts unfriendly pressure on foundations and may cause cracking and the exposure of the rebar inside to moisture.  That rebar is important for the foundation’s strength, and if it rusts, the integrity of the foundation is at risk.  So protect the whole system by getting the water away from the home.
  4. If you have a drainage system, make sure that the grates over it are cleared of leaves to allow the water to filter into it.
  5. If you have a sump pump, consider upgrading from the standard type that operates on electricity only to one that works with a battery backup.  In really big storms, we can lose power and then the regular sump pump won’t work, just when you need it most!  If you already have a battery backup, consider keeping a replacement battery on hand.
  6. Most Silicon Valley homes have power lines rather than underground utilities.  Have a look at yours, if applicable, and see if there are tree branches too close to the lines.  Often P, G & E will trim them for free if you spot a problem and let them know.
  7. Do keep spare batteries, water, food, medicines, and other essentials on hand in case of a prolonged power outage.  I recommend getting cell phone or other electronic device battery backups.  Again, if you’re out of power for 3 days, you may need something to juice up your mobile phone!  I have a couple of these “bricks” but my favorite is called a PowerStrip and it has a solar charger.
  8. If you are in an area which is heavily wooded, or the access to your home is heavily wooded, consider purchasing power tools to clear trees that may fall on your route.  Being able to get in and out is crucial in case of an emergency.

Due to an avalanche of spam comments, I have had to turn off comments on this blog, but if you think I have missed anything, please email me and I will edit this article to help others be better prepared for the rains that we hope and pray are coming soon.