I have lived near San Francisquito Creek since 1968 and used to swim in it as a Stanford graduate student. I bought a house on Oak Court off Woodland Avenue in 1975 because of the creek nearby. It is a magical and almost natural place that, most of the time, is good for the soul in its natural state.

I also attended the JPA meeting remotely. Several matters at the meeting and in the Almanac article troubled me:

1. "...flood walls 1,000 feet in length and 1 or 2 feet in height..."--Let us be very clear. What this really means is taking out all trees and all vegetation, and then creating concrete channels like the ones in south Palo Alto that were designed by Valley Water.

2. "...the hydraulics at the creek's [sic] have changed." Really? It seems that the creek has been flowing into the Bay for thousands of years. Is it possible that "climate change" has altered the creek? It seems far more likely that the engineers who built the model were wrong. However, blaming the problem on the creek or hydraulics theory makes me mistrust the engineers who are doing the analysis. Making a mistake is normal and excusable; finding a scapegoat for a mistake makes me distrustful of those who are suggesting it.

3. "The existing model...relied on data from four prior storms, all of which were less severe than the one that occurred during New Year's Eve."--While there was some flooding in late December, it was far less severe than the 1998 flooding even though the storm itself was more severe. I asked why that would be at the meeting and was told that the local jurisdictions had improved their storm-sewer capacities. This suggests that there are, indeed, other solutions to the problem that are more effective and possibly less costly than the $58 million replacement of the Pope-Chaucer bridge.

It is essential that we hear from more experts than those who have only concrete channels in their tool bag.

--Chuck Bernstein, 444 Oak Court, Menlo Park

Valley Water is showing that if Pope-Chaucer was replaced, their updated modeling (based on the actual water levels observed and documented durring the New Years Eve flood) shows that there would need to be 4 miles of 3 foot to 6 foot floodwalls from the Newell Street Bridge up to almost Pope Chaucer. 3 to 4 feet plus up to 2 feet additional on outside curves.

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Jack Xu, a Professional Engineer & Certified Flood Manager in the Valley Water Hydrology, Hydraulics and Geomorphology Unit, presented this conclusion in his June 8, 2023 presentation to the SFCJPA:

"Transfer of Flood Risk
Pope Chaucer cannot be replaced without a significant increase to the Reach 2 Proiect
• Floodwalls 3' - 4' for 2 miles on each side, from Newell Road up to almost Pope Chaucer"

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In Xu's June 5, 2023 technical memorandum, he added:

CREEK SUPERELEVATION
Creek superelevation is a phenomenon that occurs when water flows around a bend in a creek.
The water on the outside of the bend moves faster than the water on the inside of the bend,
which creates a higher water level on the outside. There are areas on the outside of bends that
are shown to have flooded on NYE, but the revised models do not. Superelevation is not
considered in the HEC-RAS model and must be accounted for separately.
Using a simple methodology from the US Army Corps, an estimate for recommended
additional freeboard due to superelevation at various locations ranges from 0.75’ to just under
2.0’

Before the JPA abandons the Reach 2 flood plan, developed over many years of engineering studies and public discussion, I would like them to get an independent, expert opinion on whether the changes to the flood model are appropriate.

Mr. Combs was quoted as saying that “science is science” so we need to accept it. Environmental modeling is an approximation, not a science. Small changes in input variables can have major impacts on the results. According to their report, Valley Water made only one significant change to the 2016 flood model: they increased the "roughness coefficient" of the creek channel until the modeled 2023 flooding between Chaucer and 101 matched the actual flooding. That is, Valley Water has recalibrated the model to fit the 2023 flood, but has not validated the revised model based on previous floods. That needs to be done.

The report concludes that the roughness coefficient was too low because the original model lacked valid data on floating debris. This conclusion raises more questions than it answers, for example:

• Do you believe that the 2023 flood is typical what we will see in the future? Have you considered that the 2023 flood occurred after four years of drought, with many stressed and dying trees primed to fall?
• If floating debris is what caused flooding to exceed earlier predictions, wouldn’t it be less damaging to the creek environment (and less costly) to reduce debris by better maintenance of trees along the creek by cities and private landowners?
• Does the revised model account for the replacement of the Newell Street bridge? If not, the conclusion that removing the Pope-Chaucer bridge will increase flooding downstream is questionable.

I hope that the JPA considers these questions (and others) before making any decisions.