Notes on meetings on recently (circa 9/97) discovered flood risks in the Matadero and Barron Creek basins

Contact: Creek Committee Chair


Abbreviation: SCVWD = Santa Clara Valley Water District

Index

Index in reverse chronological order (most recent first); rest of page in forward chronological order.
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Edited versions of tables presented at Public Meetings

Flow Rates for Storm Frequency
Flood Frequency (Probability)Barron CreekMatadero Creek
5-year (20%) 210 1460
10-year (10%) 320 1960
25-year (4%) 490 2590
50-year (2%) 620 3060
100-year (1%) 760 3500
500-year (0.2%) 1100 4480
Flows in cubic feet per second (cfs)
Barron Creek flow measured at Foothill Expressway
Matadero Creek flow measured at Louis Road
Graphical Representation of above table (20 KB)

Matadero Creek Interim Fix Alternatives
Level of Flood Protection
OptionMax Diversion from Barron to MataderoMataderoBarronNumber of homes affected by 100-year flood
1. Do Nothing600 cfs 50-year = 2.0%100-year = 1.0%3,000 +/-
2. Fully block the diversion structure0 cfs100-year = 1.0%5-year = 20.0%1,000 +/-
3. partially block300 cfs100-year = 1.0%20-year = 5.0%1,000 +/-
4. less blockage300-600 cfs 70-year = 1.4%70-year = 1.4%4,000 +/-
5. Raise flood walls at Waverley600 cfs 50-year = 2.0%100-year = 1.0%3,000 +/-
Note: flooding levels are stated in the two common formats: (1) average interval over the longterm, (2) percent chance of that level of flood happening in any given year.
For example, a flood that is projected to happen 10 times in a 1000-year interval is referred to as a 100-year flood or a 1% event.
The calculations of the size of these events is based largely on mathematical models, backed by some actual measurements and experience.


Notes from preparatory meeting involving BPA, SCVWD, and City of Palo Alto (on 10 October 1997)

Marking changes: changes since the original issuance of these notes are indicated by introductory words in the color blue.
These notes have been edited to remove sections relevant only to the preparation for the public meetings (which have now taken place). These sections have been moved to a subsidiary page with links left here.
Option numbers updated: the options presented in the sheet handled out at the public meeting were numbered differently from the preliminary version. These notes on the preliminary meeting have been updated to use the later number scheme (with the earlier number in parentheticals).

Attendees

These notes do not follow the exact order in which they were made, but have been reorganized for brevity.

Introduction (BPA)

Presentation of options: SCVWD-Chesterman

Zlotnick: "traditional level of service from the Water District not enough"

City of Palo Alto will do additional cleanup along Barron Creek

Background: the Barron Creek flood of 1983 that flooded large portions of neighborhood is classified as a 17-year event. No one knew what the classification of the larger 1955 flood was.

Sandbags:

Miscellaneous topics

Meeting announcement

Presentation at meeting


Notes from Public Meetings (Wednesday & Thursday October 15-16)

The two meetings had very similar presentations by the Water District (as they planned) and the set of topics covered by the audience was very similar, although the amount of time spent on each varied more than I would have expected. Most of the issues and concerns raised in the meeting of Friday 10 October (between the BPA Board and the Water District) were echoed by the general audience in these meetings. I will not repeat those here.

NOTE:The numbering of the options in the handout at the general public meeting was not the same as in the handout at the preliminary meetings. So be careful with any document that identifies options only by number.

When the SCVWD staff report on comments and suggestions received during these meeting is completed, they promise to post it on their Hot Topics page on their web site.

The SCVWD Board of Directors will consider which option to adopt at some subsequent board meeting. This may be at one of their regularly scheduled meeting (every other Tuesday, starting at 9am, at their headquarters in San Jose), or it may be a special meeting. There was strong sentiment (especially at the Wednesday meeting) to try to have that meeting in Palo Alto so that interested residents could attend.
Zlotnick was supportive of this (and he may have originated the suggestion), but could not promise that it would happen (it is a decision for the whole board).
Letters are being sent by BPA requesting that meeting be held in Palo Alto to facilitate public attendance (to Board of Directors, Santa Clara Valley Water District and to Mayor Huber and Councilman Rosenbaum (City of Palo Alto) requesting support)

Additional information on how the Louis Road bridge causes flooding at Waverley

The clean-out of vegetation in the Barron Creek sediment basin (behind Gunn HS) is awaiting approval (being delayed by) US Fish and Wildlife Service (issue raised in preparatory meeting).

Other public officials present (observing) at the Thursday 16 October meeting

Discussion of assignment of risk

Demolishing the Louis Road bridge

Sediment build-up in lower creek channels, and problems with US Fish and Wildlife Service (no problems with California Fish and Game)

Update: In week of Oct 27th, bulldozers have been working in lower Matadero Creek removing silt and vegetation.

Concerns about how high the water got in lower Matadero in 1995-6.

Motivations of SCVWD directors representing districts other than ours.
Option 4 and 5 in the table above are not favored by the Water District staff because they would cause flooding for homes not currently in the 100-year flood zone, and they have a dictate of "First, do no harm." This leads to the conclusion that it is better to leave 1000 homes in a 5- or 20-year flood zone, than to add 20 homes to a 50- or 70-year flood zone.
Reading between the lines: the district seems to more concerned about successful litigation by homeowners placed into the flood zone than litigation by homeowners left in the flood zone.
These priorities of the staff may well reflect the priorities that the Board of Directors bring to the meeting that decides this issue.
Aside: the people affected by this problem vote for only one of the five board members representing districts and for one of the two at-large members.



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