Ten percent or more of Delaware’s land mass could be submerged by rising ocean waters by the end of the century, and that would include up to three-quarters of the Port of Wilmington, as much as a fourth of coastal industrial land, and virtually all of the state’s extensive tidal wetlands.
More than 60 percent of dams, dikes and levees could be inundated; sections of railroad flooded out, some roads and bridges made impassable, and up to a fifth of wastewater treatment plants knocked out as an anticipated one-meter rise in sea level spreads across the low-lying state.
Homeowners, business people and government officials face widespread disruption and increased costs ranging from higher insurance premiums to relocation or construction of flood-resistant buildings. Some coastal farmland may be ruined by salt water; aquifers could be contaminated, and already-endangered species of birds and animals would be driven out of their habitats.
It’s not a doomsday scenario from the latest Hollywood blockbuster but a sober projection of Delaware’s vulnerability to rising sea levels from the state’s Department of Natural Resources and Environmental Control.
After more than a year’s work, DNREC’s Coastal Programs team has released a long-awaited draft of its vulnerability study, not yet to the public, but to the state officials, nonprofit groups, academics, and business people that make up its Sea Level Rise Advisory Committee.
Further Effects
of Sea Level Rise
Port of Wilmington could be among hardest hit by rising seas
128 acres, or 59 percent, of the land operated by the Diamond State Port Corporation, the port’s owner, would be inundated if sea level rose by one meter.
The 230-page document, entitled “Preparing for Tomorrow’s High Tide,” is the most detailed study yet by any U.S. state into the threat posed by rising ocean waters, officials said. The effort is being watched by other states and the federal government as a template for how to deal with a phenomenon that experts say is already responsible for flooded coastal impoundments, depleted farmland and dying vegetation in coastal locations around Delaware.
“This document is the first of its kind to provide detailed estimates of numbers or acres of resources at risk from sea-level rise at a state level,” the report said.
After possible revisions from committee members, the report is expected to be released to the public in May or June. It looks at the threat posed to public safety and infrastructure; the economy and society, and natural resources, and ranks the exposure of locations and facilities within each category.
Dams, railroad lines, heavy industrial areas, tidal wetlands, and the Port of Wilmington are among the highest areas of concern, while residences are of moderate concern, and factories and farmland are rated as areas of low concern.
The study deals only with vulnerability to sea-level rise; the response to the problem is due in a later study on how the state might adapt to the rising waters. Officials hope to publish initial recommendations on adaptation this fall.
“Right now, we are at the stage of figuring out where the water is going to go and how vulnerable we are to that,” said Delaware Coastal Programs Administrator Sarah Cooksey, at an April 5 meeting that presented the report to the advisory committee for the first time.
The authors base their projections on research showing global ocean levels are rising by 0.07 inch a year, or seven inches a century, as global warming melts polar ice caps and expands ocean waters.
In Delaware, the sea level is rising twice as fast as the global rate because movement in the earth’s crust means the state’s land is sinking at the same time. Tide gauges at Lewes show waters rising by 0.13 inch a year, or 13 inches over 100 years.
But even that increase is below DNREC’s projections because sea-level rise is expected to accelerate in coming decades. The new report bases its vulnerability assessment on three scenarios: that seas will rise by 0.5 meter, 1 meter, or 1.5 meters by 2100.
Statewide, the land mass lost by the end of the century is projected to be between 8 and 11 percent, including wetlands, the report said. Sea-level rise of one meter could submerge 10 percent of the state’s land.
“Because of its location and dependence on the coast, Delaware is particularly vulnerable to the effects of rising sea levels including loss of low-lying land and structures; saltwater intrusion into ground and surface waters, and increased coastal flooding from storm events,” the report said.
It argued that officials, businesses and individuals “rarely, if ever” consider sea-level rise in deciding where to build or what to preserve but may be able to protect their investments and their safety by incorporating rising waters into their plans.
“Accounting for changes in sea level that may be expected to occur over the lifetime of these projects will help lead to informed decisions for public and private investments by minimizing risk and potential for damage,” the report said.
Under the central assumption of a one-meter rise, 59 percent of the core property at the economically vital Port of Wilmington, or 128 acres, would be inundated, the report says. That would rise to 73 percent if seas rose by 1.5 meters. An additional 362 acres of supporting activities such as warehouses and dredge-disposal sites would also be flooded out.
Further Effects
of Sea Level Rise
Rail-line flooding could cause widespread disruption
The report concludes that 4 percent of Delaware’s rail lines are in areas that would be inundated if seas rose by one meter.
Heavy industrial areas identified by the state’s Coastal Zone Act are also at high risk of inundation. The report says 16-25 percent of those areas could be flooded by rising seas by 2100. While modeling suggests the factory buildings themselves are at low risk of flooding, associated structures such as docks and piers are more likely to be affected, and that could hurt local and statewide economies.
Inundation of areas zoned for future development could also cause economic damage if businesses decide not to locate there because of the threat of flooding, the report said.
The report applies the words ‘could’ , ‘might’ or ‘may’ to its projections because other factors will also contribute to the projected inundation, said Susan Love, a planner in the coastal programs unit. Models used in the study don’t account for shoreline erosion, natural migration of coastline, or human structures such as sea walls or dikes.
Love added that buildings, industrial sites, or natural features within the flood areas won’t necessarily be negatively affected. For example, a home could be elevated on pilings or a wetland could accumulate sediment, allowing it to keep pace with sea-level rise.
The threat to homes is less severe overall – between 1 and 5 percent of residences statewide are projected to be inundated by the end of the century, representing between 4,000 and 20,000 homes.
Under a one-meter rise scenario, the percentage of homes under threat ranges from less than 1 percent in New Castle County to 8 percent in Sussex County because resort development there has resulted in high-density residential development in tidal zones such as at Bethany Beach, South Bethany, and Fenwick Island.
Public water supplies, which are heavily dependent on groundwater, are also at risk if rising seas contaminate rivers, creeks and aquifers, the report said. If seas rise by one meter, three percent of the state’s “undeveloped recharge areas” – where rainfall replenishes aquifers – would be inundated with salt water.
Tidal wetlands such as Bombay Hook and Prime Hook National Wildlife Refuges would be effectively wiped out, the report said. It estimates that 99 percent of those areas would be inundated if seas rise by one meter, eliminating the wetlands’ value as carbon sinks and filters of pollutants such as nitrogen runoff from farmland into the Delaware Bay.
The coastal flooding would also further imperil endangered bird species such as the Black Rail, 99 percent of whose habitat would be lost if seas rose by 0.5 meter.
People who live in coastal areas would experience sea-level rise most directly but its impact would be shared throughout the state through the higher cost of maintaining infrastructure, a shrinking tax base, or loss of recreational opportunities, the report said.
The team assessed exposure to sea-level rise via a multi-stage process that began with data collection for facilities such as railroads, ports and bridges, and ended with a risk-assessment exercise that evaluated the geographic areas where inundation would occur; how widespread its impact would be, and how severely the location’s function would be affected.
Further Effects
of Sea Level Rise
Rising seas would inundate most dams and levees
More than 60 percent of Delaware’s dams, dikes and levees, or some 31 miles’ worth, would be inundated by a one-meter rise in sea-level, the study said.
For example, inundation of heavy industrial areas in New Castle County would be geographically limited to that area but its economic effects could be seen in job losses statewide if those factories were forced to shut or curtail their operations. The assessment also took into account the functionality of a targeted location. A tidal wetland, for example, would be identified as an area of high concern if, as a result of inundation, it was unable to perform its function of providing a wildlife habitat and coastal storm protection.
In the economically important tourism industry, business is likely to be hurt by rising seas, the report said. It projected that coastal restaurants and shops will face more frequent closures because of flooding, as well as the costs of flood defense or even relocation to higher ground.
Scenic coastal roads such as Route 9 are more likely to be closed by floods, while the state parks that attract many visitors are also threatened. The report projected that 31 percent of state-park acreage could be inundated if seas rise by one meter.
Karl Kalbacher, director of economic development for New Castle County, and a member of the sea-level rise advisory committee, said the report’s conclusions shouldn’t be a surprise given DNREC’s earlier publications and its public meetings on the issue late last year.
But he said it will probably be a “wake-up call” to some sections of the public, and to policymakers who will have to decide how – not whether – to respond to the threat to such important facilities as the Port of Wilmington and the City of New Castle.
Policymakers at state and local levels will have to decide whether to defend important public infrastructure against rising waters or simply to retreat, he said.
“I would find it troubling if we didn’t protect the Port of Wilmington and historic areas of New Castle,” he said. “They are issues that we are going to have to work through with our elected officials.”
