With sea-level rise threatening to overwhelm Palo Alto's levee system and imperil thousands of properties along the bayfront, city officials agreed on Tuesday night to begin crafting a policy for dealing with the slowly creeping menace.

In a special meeting to discuss the topic, the City Council emphasized the importance of starting to deal with the issue, even as members acknowledged that much uncertainty remains about what should be done. Once in place, the policy would allow the council to pursue zoning changes, building-code revisions and other policy shifts aimed at protecting flood-prone areas from the rising tide.

The city's effort will be informed by a series of studies and regional efforts that are concurrently under way throughout the region. Palo Alto is a partner in the San Francisquito Creek Joint Powers Authority (JPA), a regional agency that is now pursuing a major study known as "SAFER Bay" (the acronym stands for "Strategy to Advance Flood protection, Ecosystems and Recreation"), which will identify ways to improve the substandard levee system that exists today.

The study will consider ways to protect the area from a 100-year flood (a storm that has a 1 percent chance of occurring in any given year) and will incorporate 3 feet of sea-level rise into its design assumptions.

Once the study is in place, the city plans to pursue its own policy, one that will consider both the best ways to protect the community from sea-level rise and the most feasible ways to pay for the improvements.

In discussing the topic, staff and the council acknowledged the many uncertainties surrounding the topic, with differing studies offering different projections.

Phil Bobel, assistant director of Public Works, said projections today range from about a foot by the end of the century to more than 6.6 feet and, in some cases, more than 10 feet. Given the differing projections, Bobel said one important principle in crafting a policy is that one "should be ready for more change."

"You could say that given this huge range of uncertainty, it actually makes sense to do things incrementally, as long as you don't give up the ability to do something even stronger in the future," he said.

Uncertainty notwithstanding, no one disputed Tuesday that the threat of sea-level rise is real. In a report, Palo Alto staff pointed to an estimate from the Pacific Institute that indicates that a 3.28-foot rise in sea level would put 220,000 people at risk of a 1 percent flood event in the Bay Area.

The cost of replacing property that will likely be at risk of coastal flooding would be about $49 billion, in 2000 dollars. And many of the impacts would go well beyond economic figures, as flooding could threaten critical municipal facilities, according to the report.

"Critical infrastructure, such as roads, hospitals, schools, emergency facilities, wastewater treatment plants, power plants and more will be at increased risk of inundation, as will vast areas of wetlands and other natural ecosystems," the report states.

In Palo Alto, the Municipal Service Center is one of several major facilities that would be particularly vulnerable. Located near the Baylands and east of U.S. Highway 101, the sprawling complex of Public Works and Utilities facilities could be cut off from the rest of the city if the highway is flooded. Other critical facilities near the Baylands, including the Regional Water Quality Control Plant and Palo Alto Airport, would also be in danger of flooding.

"The overall result of both sea level rise and possible changes in precipitation patterns is that low-lying areas surrounding the San Francisco Bay will experience more frequent and severe flooding," according to the report. "Areas that are typically flood-prone will be inundated, and some areas that are currently not at risk will be periodically flooded."

Given the potential for devastating floods, the council agreed that the city should move ahead with a formal policy.

"We're talking about an existential threat to large parts of Palo Alto," Councilman Cory Wolbach said Tuesday, in advocating for crafting a policy.

Mayor Pat Burt also supported a new policy and said that pursuing it is "the right thing to do." He also suggested that once the policy is in place, the city can consider zoning changes to protect areas from sea-level rise.

In considering a new policy, Public Works is planning for a 55-inch sea-level rise by 2100. Strategies will focus on protection, adaptation and, where applicable, retreat, according to Bobel.

Funding is also a key consideration, the council agreed. Councilman Eric Filseth noted that if it falls to the people in the flood-prone areas to pay for the improvements, financing the projects could take many decades.

"If we have an assessment district, it seems like it's got to be done pretty soon because it's going to take a lot of time to pay for it," Filseth said.

The San Francisquito Creek JPA is meanwhile pursuing its own strategy for financing the needed improvements. As a long-term goal, the agency plans to bring a ballot measure before voters to create a special tax to fund construction of the needed tidal levee improvements. The projects will be designed to bring about 2,700 Palo Alto properties out of the flood zone, as designated by the Federal Emergency Management Agency (FEMA).

The city's existing levee system -- a network between the creek and the Mountain View border -- is considered substandard and does not meet FEMA standards for height or construction quality, according to Public Works.

Related content:

• Report: Cities unprepared for sea-level rise

• Experts: Rising sea level needs to be top priority