mike koozmin/the s.f. examinerJust south of AT&T Park

Study: SF may need to build levee to protect Mission Bay from rising sea levels

San Francisco may get a wall on the waterfront after all.

But this barrier would not be a block of condominiums for the rich to live in, as the former 8 Washington St. project proposed. This wall is needed to keep the ocean from flooding The City's newest hospital complex and the Warriors' new arena.

Mission Bay is one of the biggest ongoing development areas in San Francisco in recent years, with a sprawling new UC San Francisco campus nearing completion. There are new condo complexes rising within walking distance of tech firms, and a stone's throw away from the Giants' waterfront home at AT&T Park, the Warriors' new arena could be open by 2018.

Mission Bay is also the first area in The City that is expected to see regular flooding — and, eventually, a new permanent waterfront formed inland from the present coast — within the next 35 years due to impending sea-level rise.

The ocean level around San Francisco is expected to rise by as much as 15 inches by 2050, according to conservative estimates.

By 2100, the ocean could rise between 3 and 6 feet, according to figures produced by the National Research Council that are accepted as realistic sea-level rise projections by The City.

“We know it's going up,” said Steven Reel, a project manager at the Port of San Francisco's engineering department. “And it will continue to go up.”

To keep the water out, The City might need to construct a levee — an earthen wall similar to barriers seen in the Netherlands and in New Orleans — on the current shoreline at Terry Francois Boulevard, according to a draft version of a study presented to The City's Capital Planning Committee on Monday.

Other options to keep the UCSF Benioff Children's Hospital, as well as the Warriors' court, dry besides a levee at water's edge include a tidal gate at the entrance to Mission Creek, and another wall further inland at Third Street. Mission Creek could also be closed off to the tides entirely in a fashion similar to Oakland's Lake Merritt, said Laura Tam, sustainable development policy director at urban-planning think-tank SPUR.

The City hopes to eventually consider the impact of rising tides when planning future development projects, and draft guidelines for incorporating requirements addressing sea-level rise could be approved in the coming months.

There's no requirement yet for private developers to plan what to do if their current-day projects become waterfront property or are subjected to flooding.

So far, private lenders are still willing to fund projects where flooding is possible, noted David Behar, chair of The City's sea-level rise committee.

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