sea level rise meet

Jake Thickman, a coastal scientist at Moffatt & Nichol, explains a sea level vulnerability map for Seal Beach last week  during a Sea Level Rise Vulnerability and Adaptation Strategies Workshop for the Seal Beach Local Coastal Program at Marina Community Center in Seal Beach.

Seal Beach residents got a look July 17 at what sea level rise could mean to them, thanks to a city presentation showing that large swaths of the small municipality could flood by 2050 and that the odds of even greater inundation will increase throughout the century.

While there was significant concern among the 40 or so residents on hand at the Marina Community Center, there also was criticism that projections of sea level rise showed flooding far sooner than was probable.

The state’s sea level projections used at Wednesday’s workshop have just a 0.5% chance of occurring as quickly as the city is expected to prepare for. State officials say those projections are recommended in order to accommodate factors not taken into account in the calculations, including indications that water rise may accelerate faster than previously thought.

“I think that’s a bit aggressive,” said Robert Goldberg, whose Clipper Way home is in an area projections show will be among the first to flood. “I’m not going to sell my house based on a 1-in-200 chance. I think something like 1% or 2% might be more appropriate.”

The workshop is part of the city process in developing its Local Coastal Plan, which will outline development and resource protection rules in Seal Beach’s coastal zone. The document will incorporate requirements of the state Coastal Act and allow the city to give final approval to new development. Because it lacks a Local Coastal Plan, the city currently must send new coastal development to the state Coastal Commission for review.

One component of the Local Coastal Plan will be how the city intends to adapt to rising seas. A preliminary report outlines a possible mix of protections such as seawalls and sand berms, accommodations such as putting buildings on stilts, and retreat, which could include abandoning and demolishing current structures.

The Probability Debate

Seal Beach is already susceptible to flooding, with a sand berm constructed on the beach each winter as protection against high tides and big surf.

According to recommended state projections, a 1.6-foot sea level rise could occur by 2050. Combined with a 100-year storm and without new mitigation, flooding from the San Gabriel River northwest of the city and Anaheim Bay to the southeast would spill over into neighborhoods inland from the beach — particularly low-lying areas south of Pacific Coast Highway.

With a 3.3-foot sea level rise by 2070, similar flooding would occur without a storm. With a 6.6-foot seal level rise by 2100 and no storm, the inundated area would roughly double with water coming from the ocean and nearby wetlands as well as from the San Gabriel River and Anaheim Bay.

But those projections have just a 0.5% chance of occurring, according to the Coastal Commission. The “likely” scenario outlined in the city’s Sea Level Vulnerability Report is a half-foot to a foot of sea level rise by 2050 and 1.3 feet to 3.2 feet by 2100.

The projections of faster sea level rise were developed by the state Ocean Protection Council and are used as recommendations by the state Coastal Commission, which must approve Local Coastal Plans.

“We want to make sure we’re not underestimating future sea level rise because the consequence to coastal resources, development, life and safety could be severe,” said commission spokeswoman Noaki Schwartz.

She said that the science of projecting sea level rise has continued to evolve since the state projections were established, including indications that ice-sheet melt may cause seas to rise faster than previously thought. That means the 0.5% probability “may, in reality, be higher,” she said.

A Harbinger

Anticipation of future sea level rise is already affecting development plans in Seal Beach.

A proposal to build two houses on a vacant lot on 17th Street, five blocks from the beach and four blocks from Anaheim Bay, has been staunchly opposed by Coastal Commission staff, which notes that 3.3 feet of sea level rise would inundate the lot.

“The proposed subdivision and construction of two single-family residences is not designed or engineered for the changing water levels and associated impacts that are anticipated over the life of the development,” says the staff report. “It is important to note that at 5.7 ft. of (sea level rise), inland flooding is so severe that the beach fronting portion of Old Town may become an island and that whole sections of sandy beach may disappear.”

At the request of the builder, a commission vote on the project scheduled for July 10 was postponed.

That situation is likely a harbinger for all coastal cities as they develop state mandated climate adaptation plans and update their Local Coastal Plans.

“What we’re after is what adaptations are most appropriate for Seal Beach,” city consultant Chris Johnson told the workshop gathering. “The most appropriate fix.”

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