Monterey facing major impact from sea level rise - The Mercury News

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MONTEREY — There will be major effects from sea-level rise on Monterey’s transportation systems, causing entire road closures, including shutting down the Lighthouse Tunnel to some 55,000 cars that make daily trips, experts explained to the city’s Planning Commission this week.

“This is going to be a slow-motion train wreck,” said Commissioner Michael Dawson about the massive infrastructure damage the rising seas could cause.

Frederik Venter of Kimley-Horn Associates and Rebecca Verity of GEI Consultants have been working with Fernanda Roveri, a senior associate planner with the city, to develop staged timelines for the years 2030, 2060 and 2100 that project what sea-level rise will do to the city’s transportation network and possible solutions to thwart massive damage that can cost hundreds of millions of dollars.

Data for the current study were generated by Revell Coastal in 2017, and the future wave impact analyses in the study were conducted by Moffatt and Nichol in 2019.

Tuesday’s meeting was designed to brief commissioners on work that has been developed over a matter of months and then to solicit public feedback about proposed solutions.

By the end of this decade, sea-level rise is projected to be in the neighborhood of 8 inches, enough to regularly flood Del Monte Avenue in the vicinity of Del Monte Beach. By 2060, the seas will have projected to rise by 2.4 feet and Del Monte will be completely underwater and the Lighthouse Tunnel will be little more than a freeway for fish.

And by 2100, the sea will have risen 5.2 feet, forcing the closure of Fremont Street, creating tremendous congestion and a significant decline in economic activity in the city. It will cause a domino effect with cars piled up on Highway 1 and one scenario has motorists wanting to go to Cannery Row squeezing onto Highway 1 then circling around on Holman Highway through Pacific Grove.

It’s not just surface streets. Sewer lines and storm drains will be severely damaged. Sinkholes will erupt where wave action undercuts surface strata. Water inundating electrical systems will spark fires. There will be an increase in traffic accidents, as well as injuries and deaths along with delayed time from first responders. Homes and businesses would need to relocate. Monterey will be a less attractive place for tourists and an economic downturn would cascade.

“It would be a less attractive place to work and play,” Venter said.

On the most basic level the city is faced with two options: let the sea come in and let it take what it will, or try to keep it out with a number of measures — none of them cheap.

One option is to elevate the current coastal Recreation Trail by 13 feet and pack the seaward side with two-ton boulders to mitigate the wave action that would pound its base. In today’s dollars that would cost roughly $57.9 million.

Another option the city could explore is to anchor massive piles in underlying bedrock and construct a 17-foot-tall seawall on the ocean side of the Rec Trail as well adding smaller rip-rap boulders. The downside to this strategy is for roughly three-quarters of a mile pedestrians would not have a view of the ocean. It’s also the most expensive seawall option at $88.9 million.

In the absence of seawalls, another option would be to construct a viaduct to the tune of $300 million that would take traffic over the top of the advancing surf line. Or, Del Monte could be diverted inland and cross newly constructed bridges across a swollen El Estero.

The study notes that Monterey is perhaps better naturally prepared than many of California’s at-risk cities. With hills rising steeply from the sea, granite rather than sandstone cliffs and its most at-risk region already centered around El Estero, Monterey may find that adapting to rising seas may also provide unique opportunities.

“By creating a tidal bay in an area not much larger than the existing Lake El Estero, Monterey could restore a coastal estuary, add rather than lose beaches, bike trails, and waterfront businesses, and create sheltered marshlands or harbors for fishing, swimming, and small boats,” a section of the study reads.

In the short-term, the city’s Planning Department has applied for two $400,000 grants with the help of the state Office of Emergency Services and the state Coastal Conservancy to move planning into the next phase that by 2025 will require a decision about the best strategy to pursue.

The city of Monterey couldn’t come close to generating the funding needed for some of the options and would rely on state and federal funding. The problem with that is Monterey is only one of thousands of coastal communities that would face the same fate by the time grandchildren today are facing the consequences of sea-level rise.

A graphic showing which streets would be inundated at various time intervals. (Courtesy city of Monterey) 

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December 12, 2020 at 08:28PM
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Monterey facing major impact from sea level rise - The Mercury News

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