Thanks to Carolyn Walker’s obtaining complimentary tickets for Woodside HOA reps, five of us were able to attend the 2023 California Central Valley Flood Control Association Forum. The CCVFCA website is here:

[The presentation has been posted online:]

These are my takeaways. If I misunderstood anything, please correct me.

The event started with a presentation by Portadam. They make temporary flood barriers, in principle similar to sandbags but reusable and easier to deploy. There is a possibility of seepage beneath the barrier, same as for sandbags, and a pump might be needed. The speaker said a four-person crew could easily set them up, and gave a ballpark figure of $220 per linear foot for a 4-foot-high barrier. More info is here:

The keynote speaker was Daniel Swain, a climate scientist who’s affiliated with UCLA, NCAR, and The Nature Conservancy. More info about him is available on his website:

Climate change is affecting California’s natural variability of seasons, and the extremes will be more extreme. There will be more intense rainfall packed into a shorter period of time. Then there will be months of drought. He mentioned the droughts will be hot rather than cold, which will intensify the drought. There will be less snowpack and a longer fire season.

For every 1° F increase in average temperature, there’s a 4% increase in the water held in the atmosphere. More evaporation, more water to dump. An atmospheric river can hold more water than the Mississippi. We could get 80-100 inches of rainfall in a month. If the mountains get rain instead of snow, there could be 2-5 times the current runoff.

The 1862 flood was a 200-year flood. I’d seen the images of boats sailing the streets of Old Sac and knew the streets were raised after that. What I didn’t know was that the entire Central Valley was flooded. That’s what we’re facing now. In 2018, there was a 50/50 risk of a 200-year flood in the next 40 years. Climate change is increasing the risk.

Solutions: Prepare for the coming floods. Millions of people will need to be evacuated, many for months and many forever. Test hard structures and plan for them to fail gracefully (in a predictable manner with the least damage).

After Swain’s talk there was a panel discussion. One of the participants was Lori Nezhura, Deputy Director of Planning, Preparedness, and Prevention for the California Office of Emergency Services. There are grants available for flood protection. We can request information by emailing Available grants are also posted at