More than 200 Ross Valley residents braved the rain Saturday morning to hear about projects to eliminate creek flooding - and an annual tax to pay for them.

The session featured an hour-long explanation by county project manager Jack Curley, who showed slides of the trouble spots, explained data from a new hydraulic model, and outlined projects that, in theory, would stop another "100-year flood" from inundating the Ross Valley.

"These solutions, according to our models, would have eliminated last year's event," Curley said of the Dec. 31, 2005, storm that devastated downtown San Anselmo.

Of the dozen or so people who spoke afterward, a woman suggested tweaking the proposed tax to make large property owners bear a bigger share of the cost, and a man proposed a fee for new development. Most praised the thoroughness of the plan.

"You're headed on the right track," said Roger Roberts of the Marin Conservation Corps.

The session, organized by Supervisor Hal Brown, came three days after Fairfax voted 4-1 to join Ross Valley's Flood Zone 9 following a stand-off with county officials over the right to veto projects town officials didn't like. The zone includes San Anselmo, Ross, Kentfield, Greenbrae and Larkspur.

Although Fairfax's decision added an air of unification to Saturday's event, Brown and others remained on the offensive.

"The longer we wait, the more expensive it will be and the harder it will be to get state and federal funds," Marin County Public Works Director Farhad Mansourian said.

Curley spent considerable time detailing a half dozen of the 16 "constriction" points that cause flooding.

They include a 500-foot culvert in Fairfax; the Lagunitas Road Bridge in Ross and a wooden fish ladder about 600 feet downstream from the bridge; and, in San Anselmo, bridges at Madrone, Nokomis and Sycamore avenues.

He said reconfiguring the Fairfax culvert and the four bridges, along with replacing the wooden fish ladder with a stone ladder, would provide enough water flow improvement so that, during a 100-year storm, a couple catch basins in Fairfax could take care of the rest.

He said Lefty Gomez Park and White Hill Middle School in Fairfax have enough space to hold the overflow.

But, he stressed the projects are preliminary because water flow data and computer modeling hasn't taken into account all of Fairfax, Sleepy Hollow and a few surrounding areas.

"These will change when we do that," he said.

Dave Dickson, a Berkeley consultant who worked on Napa's flood program and presented the financial component of Saturday's workshop, said Flood Zone 9 brings in $140,000 annually and that $660,000 kicked in last year by local governments is already gone.

Regions that have solved nagging flood problems have all created a dedicated, reliable funding source to pay for repairs.

"That is what is needed here," he said.

Dickson touted a recent mail-in survey, which indicated 67 percent of the 1,500 responding Ross Valley property owners said they supported a "storm drain user fee" proposal that officials say requires a simple majority vote. No one discussed the Proposition 13 rule that special taxes require a two-thirds majority vote.

He also explained how officials created a formula that has four annual "user fee" or parcel tax payment tiers ranging from $104 to $180 depending on the amount of impervious surfaces on a parcel.

A Ross Valley flood tax would generate $40 million over 20 years - when it would sunset - and create opportunities for other low-interest loans and grants that requiring matching funds, Dickson said.

Fairfax Mayor Larry Bragman, who cast the lone dissenting vote on the Town Council against joining the flood zone, called the project and funding presentation "overwhelmingly impressive."

He said he remains skeptical that Fairfax will receive a good return on the tax. He said the Fairfax culvert isn't at the front of the line of improvement proposals and it will likely require buying several properties.

"That's a big project," he said.

Assemblyman Jared Huffman said project managers have done an excellent job figuring out what needs to be done and presenting a case to finance repairs. That puts the plan in a good position for state and federal money, he said.

"I'm very excited by this," Huffman said.