from Sea Level Rise Vulnerability and Adaptation Workshop document
Map of Imperial Beach in 2100 projecting extent of flooded streets
Imperial Beach residents got a "scary" look at how the city will be affected by rising sea levels Wednesday night (May 11) and began looking at ways to keep the beach in Imperial Beach.
"If we don't do anything, we're going to have a much wetter Imperial Beach," said David Revell, a geomorphology scientist and consultant who specializes in sea-level rise in California. "If we don't do anything, we will have more disasters at rising costs." The meeting marked the beginning of what city leaders described as a conversation on how to deal with the predicted rise in sea levels over the next 100 years.
Sea level is expected to rise to two meters (six and a half feet) by 2100, said Revell, and the rise is accelerating in large part due to increasing melt of polar ice and a rise in water temperatures that's causing water to expand.
"It isn't rising linearly, it's rising exponentially," he said. It isn't new but it has sped up. Sea level from "a 50-year storm event [likely to happen once in 50 years] in 1950 is now a normal high tide."
The “scary” maps, he noted, are based on predictions of what could occur over the next 100 years if nothing is done. Under those projected conditions, at a two-meter increase in the sea level, 30 percent of the parcels of land in Imperial Beach are at risk of flooding or erosion.
City leaders hired Revell to study the city's vulnerabilities so they can begin working on long-term strategies for protecting property and beaches and still respect the environment and natural processes.
The April flooding in the southwest areas from the Tijuana River mouth blockage is still fresh in people's minds. One frustration, voiced by several councilmembers, is that the solutions have to be regional. Though other cities and the port were invited to participate in the "workshop," none showed up.
"What I am concerned about is our missing partners," councilmember Lorie Bragg said.
The coastal city of about 27,000 people is particularly vulnerable because of geography, councilmember Ed Spriggs said. "We don't have a choice because we are surrounded on three sides by water and because we are a low-lying community. The more we look at these options, the less we will be driven by fear."
The city is looking at ways to adapt to higher sea levels that include: coastal armoring with sea walls; continuing to add sand to the beaches to add more buffering; a hybrid of combining dunes and cobble along the coast; extending the existing jetties (called “groins”) and adding several more to increase the build-up of sand offshore; and, buying the land along the coast and leasing it back to residents and businesses until it is no longer safe to use for people, and then surrendering it to the ocean.
Each approach has its drawbacks. Experience shows that building sea walls results in the sand at the foot of the wall eventually disappearing, for example.
"If we do nothing but hold the line and armoring, we lose the beaches by between 2050 and 2075," Revell said. Sand “nourishment,” will cost an estimated $20 million for Imperial Beach alone, Revell said. And the hybrid combination of cobbles and sand to shield the city's beaches will have to be rebuilt between four and seven times in the next 94 years, he said.
A lease-back arrangement will be very expensive in the long term; Revell estimates that by 2100, the ocean will claim land three parcels deep along the coast. Workshop participants pointed to Santa Monica's accidental solution — its breakwater (built in 1934 to make a wave-free marina, and quickly overtaken and submerged) has protected the city. Revell said it was a possible solution, but not among the top five suggested. The city's best bet is to choose different strategies for individual issues, he said. Revell emphasized that the city has time to take a thoughtful approach to addressing the problems.
Former congressman and longtime Imperial Beach resident Brian Bilbray said that the public's commitment to protecting the city has to remain strong.
"The biggest problem is when it's time to move forward, the public that was for it doesn't show up but the small group of people who oppose it do," Bilbray said. "Every one of these answers has to have [the leaders with] the commitment and the fortitude [to face] being attacked."
Bilbray noted that coastal erosion was the first issue before Imperial Beach in 1956, when it became a city.