New maps show risks for flooding in Humboldt Bay
11/19/13
It will not be long before the coast of Humboldt Bay looks dramatically different.
The Humboldt County Public Works Department and Humboldt Bay Harbor, Recreation and Conservation District hosted a public information meeting to discuss rising sea levels around Humboldt Bay on Nov. 12.
Jennifer Kalt, policy director of Humboldt Baykeeper, said they discussed the vulnerability of the earthen dikes surrounding Humboldt Bay. The dikes were built in the late 19th and 20th centuries and have not been properly maintained, according to Kalt.
New inundation maps were released for the first time at the meeting, which is part of the Humboldt Bay Sea Level Rise Adaptation Planning Project.
The goal of the mapping is to determine which areas need to be protected by armoring the existing dikes and which areas will be allowed to turn back into wetlands.
“We’re going to be one of the first places that is going to have to make the difficult decisions as the sea level rises,” Kalt said.
Kalt explained that in the past few years Humboldt Bay has been experiencing twice the sea level rise of the California average.
“Between two and three feet of sea level rise is the point at which most of the former tidelands will be flooded,” she said.
Most vulnerable to flooding from storm surges are the Arcata and Eureka wastewater treatment plants due to their location. Highway 101 between the two cities is also at risk.
Up to 90 percent of local wetlands were diked off and turned into agricultural land Kalt said.
“The former salt marshes that are now pastures behind the dikes have dropped two to three feet due to land subsidence,” she said. The subsidence and rising coastline leave these areas vulnerable.
The Coastal Commission is calling for all new building projects in the coastal zone to plan for an additional 18 inches of sea level rise by the year 2050.
The sea level is expected to rise as much as 55 to 65 inches by the year 2100, according to the National Research Council.
“It is important to note that although the timing is uncertain and predictions will change with more info, sea level rise is happening and we need to plan for it,” Kalt said. “That’s the big lesson: building and developing wetlands isn’t really going to get us anywhere.”
Dan Berman, who is a part of the project and works for the Humboldt Bay Harbor District, said there are two main components to what the group is working to do. One component is the technical work of mapping and modeling and the other is analyzing that data and looking at case studies to determine what the options are.
“Part of our goal for this is to share information with the community,” Berman said.
Aldaron Laird, environmental planner and owner of Trinity Associates, said the purpose of the meeting was to show the public the inundation footprint.
“We showed what the potential for flooding is based on the existing conditions of the shoreline,” Laird said.
According to Laird, 75 to 80 people attended the meeting last week. The group plans to hold public meetings annually.
