DFM News' five part series on the potential impact of sea level rise in Delaware continues with Part IV - the third and final stop on our county-by-county look at the issue, Sussex County.
In the City of Lewes, an expected rise in sea level is an integral part of a new report on hazard mitigation and climate change adaptation.
The document, published in June and approved in early August by the city council, notes that the city has already seen its coastal waters rise by 12.7 inches over the last century, and the waters are expected to rise faster in coming decades.
“Sea-level rise will pose many and varied threats to Lewes,” the report said. It anticipates flooding will be more frequent; will reach further inland, and will exacerbate erosion. Some areas that now flood only during storms will become permanently inundated.
More than a third of the city’s buildings are in an area designated by the Federal Emergency Management Agency as a 100-year floodplain, which is deemed to have a 1 percent chance of flooding. An event of that nature would cause some $24 million worth of damage, and the risks will increase as the climate changes, the report said.
“Climate change will impact Lewes directly through continuous sea-level rise, increased coastal erosion, changes to wet-dry seasons that can cause both severe drought and higher precipitation, and associated floods that impact both natural systems and the built environment,” the 171-page report says.
As part of the mid-Atlantic region, Lewes is vulnerable to the warming temperatures and rising sea levels that most scientists see as “extremely likely” by the end of the 21st century, according to the report, which was prepared by the University of Delaware’s Sustainable Coastal Communities Program, the Delaware Sea Grant College Program, and ICLEI, an association of local governments working on sustainability projects.
Like other coastal communities, the city will be subject to accelerated sea-level rise over the coming century as glaciers melt and water expands due to temperature increases.
The Lewes report cites a 2007 study by the United Nations’ Intergovernmental Panel on Climate Change which projected a global sea-level rise of 0.59 to 1.9 feet, based solely on the thermal expansion of water. That estimate doesn’t include the effect of glacial melt which could push the global increase as high as 4.6 feet over the next century.
Coastal storms will be more frequent and more damaging, the report says. It cites a study of Atlantic City, NJ where “100-year” (1 percent chance) storms are projected to occur as often as once every four years by 2050 and once every two years by the end of the century.
For Lewes, bigger, more frequent storms and higher seas would damage commercial, residential and industrial buildings as they move farther inland. Sewers and septic systems would be flooded and aquifers could be contaminated with salt water.
Among “critical facilities” in the town’s 100-year floodplain are the Cape May/Lewes ferry terminal, the U.S. Coast Guard station, three University of Delaware buildings, and the town’s wastewater treatment plant.
Flooding of the wastewater plant would pose a serious threat to the health of the town if it was unable to process water, the report said. “Flood damage could result in a failure at the plant that might lead to an overflow of the plant’s contents, resulting in a serious health risk to the community,” it said.
Lewes Mayor James Ford said he can’t conclusively link recent local events like flooding or beach erosion to sea-level rise, which is just one of the natural hazards that the city is planning for.
But he acknowledged the growing weight of research indicating the likelihood of higher sea levels in the future, and said his city would be foolish to ignore it.
“For the most part, the writing is on the wall that some things are changing,” he said.
Rising Threat: Lewes braces for ‘greatest threat’ of sea-level rise
Excerpts of interview with Lewes Mayor James Ford
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In the case of the “nor’easter” storms that periodically flood sections of Lewes, there’s no evidence so far that they are being made any worse by rising seas, Ford said.
“But if there’s even the slightest elevation in sea-level rise then it certainly would exacerbate a northeast storm,” he said.
Local memories of recent storms are fresh as evidenced by a sign posted along the main road linking the Lewes town center with its beachfront. The sign, at the edge of a marsh, commemorates a 1998 storm in which the water rose 5.1 feet above mean sea level, covering the street where the marker stands with almost two feet of water.
The sign also has a picture of a flooded gas station and a yellow van up to its axles in water during a 1962 storm when the water rose 7.8 feet above mean sea level.
Among a long list of recommendations for dealing with the expected rise in sea level, the report urges a review of the city’s zoning code to ensure that flood regulations are strengthened and buffers around wetlands are increased; improved protection of water wells against a possible influx of saltwater, and better stormwater management.
The city should also conduct a survey of vulnerable homes based on their heights above expected flood levels; provide additional financial incentives for homeowners to build above code requirements; increase education for homeowners on how to build and retrofit to withstand flooding, and increase understanding of how aquifers work, the report said.
Changes to building regulations could increase construction or renovation costs for homeowners but those costs could be offset by reduced insurance rates if they are cut under the Community Rating System, Ford said.
Although residents are likely to question any such changes proposed by the council, they would likely accept them as they become more aware of the threats involved, he added.
“I would expect there to be questions, but I also feel the residents and property owners understand the concerns and challenges they face living in that location,” Ford wrote in an email.
Planning and zoning codes should reflect the expectation of sea-level rise, the report said. Such changes would allow Lewes to maintain its relationship with the sea, which it called a “core community value.”
It also calls for the city’s Comprehensive Plan to include language recognizing the severity of the threat of rising seas.
“The greatest threats to the community come from rising seas,” the report says. “Looking forward, scientists have confirmed the seas will rise at an accelerated rate this coming century. In Lewes, this rise will very likely cause flooding to cover more land and reach high elevations on already designated flood zones.”
Development that does not account for increasing inundation levels puts homes, business and infrastructure at risk resulting in human hardship and higher costs to government for response and recovery, the document says.
“Given that Lewes is already vulnerable to storms and flooding events, these increased threats from climate change are of even greater concern to our community.”
Next in the Rising Threat series: A look at the how the state's public policymakers plan to prepare for sea level rise.
Previously: Part I - Rising seas threaten Delaware coast, test policymakers.
Part II - City of New Castle plans dike repair to repel rising seas.
Part III - Distant scenario or current menace in Kent County?