A wetter future only seemed more inexorable this month, with Typhoon Haiyan laying waste to the Phillipines with a 14-foot storm surge, and new flood maps issued by the Federal Emergency Management Agency bringing back the high-water mark deep within cities. For planners, the work is a mix of keeping water out and letting it come in and recede, and calculating scenarios aimed at the "fewest regrets,' according to senior fellow Armando Carbonell, who appeared on the panel Planning for Coastal Storms at ABX Boston last week.
"We can't predict exactly how warm things are going to be, or how much the sea level rise is going to be," Carbonell said, so the challenge is to plan for a certain amount of uncertainty, within a range of likely impacts.
Adding to the difficulty is the fact that FEMA flood maps alone can’t be used as a planning tool, because they are based on historical data and do not anticipate changing conditions. The maps are primarily for insurance purposes, though "planners use them for planning because that’s what they have," Carbonell said. The resilience task force being led by HUD secretary Shaun Donovan suggests using information based on the latest available technology, and adding a measure of safety on top of that.
The Netherlands combines barrier infrastructure with designated areas where flood waters are allowed to flow in and then recede, anticipating the so-called "periodic occupation" of hazard. The City of Hamburg takes a similar approach of floodproofing along with floating docks, floodable promenades and parks, and buildings and streets positioned to be out of harms way, eight meters above the Elbe River. Facilities are pulled back from the shoreline and separated by a natural buffer designed to absorb flood energy, at the Hunters Point naval shipyard on Treasure Island in San Francisco.
Two recent publications, Resilient Coastal City Regions and Opening Access to Scenario Planning Tools, provide more background on current adaptation strategies.
The most vulnerable and typically hardest-hit areas are the most heavily urbanized. But most storm-related fatalities occur as people are moving through the flood event -- driving or walking -- suggesting a lack of confidence in the safety of the built environment, noted Ken Buckland, principal at The Cecil Group.
Also in the session, Gregory Sampson, an attorney at Robinson & Cole, detailed the 2012 reforms in the National Flood Insurance Program, which phases out subsidies for second homes, limits severe repetitive losses, requires that rates cover actual losses, and creates a reserve fund. The changes, he said, have the support of both environmentalists, as high premiums will discourage reckless building and occupation, and fiscal conservatives, due to the elimination of subsidies.
Boston, in addition to adopting climate change preparedness and resiliency guidelines, is considering a local wetlands ordinance based on future seal level rise of up to three feet, requiring builders to show buffer zones and development features to let water through ground floors and basements. The techniques are necessary in part because environmental regulations increasingly prohibit building hard infrastructure such as a sea wall, he said.
The only option is retreat for a growing number of places suffering from beach erosion. For others, the emphasis is on elevation, as well as a new industry in building techniques and materials, from "breakout panels" designed to give way in a storm, to wind-resistant building frames, sliding doors and windows, said Charles Orr, principal at Hutker Architects. There is already a greater reliance on exterior materials such as stone, zinc-coated copper, and uncoated natural woods that reflect the "new coastal ethic," he said.