Zusha Elinson/The Bay Citizen

The site in Redwood City where Cargill wants to build as many as 12,000 new units of housing

New developments on the shores of San Francisco Bay won't be approved unless they offer economic or environmental benefits that outweigh the cost of protecting against rising seas, under rules adopted Thursday by regional leaders.

The new rules, written to reduce the risk of flooding as the climate changes, are the most advanced and detailed of their kind in the nation.

“What we’re doing today goes beyond the Bay Area,” San Francisco Bay Conservation and Development Commission Chairman Sean Randolph said before joining in a unanimous vote to approve the guidelines. “It has national significance.”

But the guidelines are significantly less ambitious than a proposal to discourage all waterfront construction that the commission, which has jurisdiction over the shoreline, initially planned.

After developers and trade associations voiced their opposition to the plan in May, the commission scaled back the proposal. On Thursday, commissioners voted 24-0 to give themselves more flexibility to approve construction proposals if the benefits of building in an already-developed shoreline area are found to outweigh the risks.

That change could help facilitate approval of the controversial 12,000-home Redwood City Saltworks development proposed by DMB Associates.

“We believe that the version adopted today removed the impediments to proactive collaboration on sea-level rise,” DMB Associates Vice President David Smith said. “Our concerns with the earlier versions of the amendments were that they established prohibitions and presumptions that would have thwarted solutions.”

Smith says the Redwood City project could benefit its neighbors by encouraging the development of a levee system to protect the area from flooding, for example.

The revisions to the guidelines convinced business groups such as the Bay Area Council to withdraw their opposition without incurring substantial opposition from environmentalists. The president of the Bay Area Council Economic Institute, which is the Bay Area Council's research affiliate, is also the chairman of the commission.

“These policies discourage projects that would develop in dumb places, and it encourages tidal marsh restoration in undeveloped areas,” said David Lewis, executive director of the nonprofit Save the Bay. “That’s what the original draft of the policies was calling for.”

The guidelines also require the consideration of the latest climate change science when considering building proposals; acknowledge the importance of wetland restoration projects and shoreline buffer zones to help nature adapt to rising seas; and call for specific additional scientific research.

Sea-level rise along the West Coast of the United States has been less pronounced than around other parts of the Pacific Ocean in recent decades, largely due to cold local waters and the temporary effects of ocean currents. But the Bay Area is considered particularly vulnerable in the future because of its many low-lying shoreline areas.

The commission is preparing for an anticipated 55-inch rise in sea levels by the end of the century, which would leave 213,000 acres of land in the Bay Area flooded or vulnerable to flooding.

The guidelines are considered the first step in preparing the region for the consequences of climate change, including potential heat waves and disease outbreaks.

That planning process, which was mandated by the Legislature and involves multiple government agencies, could take a decade or more to complete.

“There’s still a lot of heavy lifting ahead as the region begins to consider what’s going to be a broader and more specific climate adaptation plan,” Randolph said.

Correction: An earlier version of this story incorrectly stated that Sean Randolph was president of the Bay Area Council. He is president of the Bay Area Council Economic Institute, which is the council's research affiliate.