By Dr. Robert Thorson
When I began teaching at UConn in 1984, I started a file of state newspaper clippings for my earth sciencecourses. One of the first things I learned was that more than 6,000 acres of wetland on the Connecticut shore was converted to dry land prior to the 1970s by ditching, draining and dumping within tidal wetlands. This allowed land-hungry communities to spread out over what was then being called artificial fill.
At the time, I wondered naively why any government would permit such land use practices during a geological epoch of melting ice sheets and rising sea level. Today, any governing entity for coastal property knows that the pace of sea level rise has accelerated, and that an epoch of stronger subtropical storms is upon us.
Within the last decade, the owners of Connecticut coastal properties have been kicked in the shins by rising insurance premiums. Now, the state and municipal governments with jurisdiction over those lands are being kicked by Moody’s Investors Service. This credit rating agency, arguably our nation’s most respected, has put coastal states and municipalities on notice that Moody’s credit ratings for state and municipal bonds will hereafter be tied to coastal preparedness.
The fiscally conservative and hazards aware part of me is loving this news because it proclaims an obvious truth that we geologists have taught for a half-century. Easy come, easy go. Lowlands created easily by shallow fill will be the first to go under. We’re talking about our national mall in Washington, D.C., much of the Bay Area in San Francisco, the Florida coastal strip, New York, Boston and countless other cities with large areas of low-lying fill within city limits.
To understand this sea change in Moody’s tone, simply pause and reflect on what the past hurricane season did to poorly prepared coastal communities. The media frenzy has abated, but the financial shocks keeps growing. The estimated recovery costs are: $180 billion for Harvey in Texas; $95 billion for Maria in Puerto Rico; $50 billion for Maria in Florida. The total is triple that of historic Hurricane Katrina, once considered the “costliest hurricane in U.S. history.”
Though the U.S. is $20 trillion in debt, each disaster is met by battalions of federal employees who coordinate recovery and help pay the bills. In Houston alone, more than 10,000 people were physically rescued, and nearly 1 million citizens have asked for financial assistance. Any money our federal government pays them will be borrowed from somewhere else. Though the size of our debt staggers belief and is beggaring the next generation, it’s only enough to pay for 61 hurricane seasons like the last one.
Continuing with the example of Houston, the Dec. 1 New York Times published an investigation about building on the city’s reclaimed marshes and swamps. In Houston, 6,000 properties were built in zones designated as safe following minor engineering alterations such as building levees and raising the land surface a few inches with imported soil. In one of these so-called safe zones, a sprawling, upscale residential community called the Woodlands was submerged by the floods of hurricane Harvey. This inundation, the paper said, “underscored the profound vulnerability of a metropolis with an ethos of untrammeled development built, essentially, on a swamp.” This quote could also apply to the development-crazed ethos of the Connecticut shoreline prior to the 1970s, after which the state stopped encouraging the filling of floodplains and coastal marshes. Everything built on those lands is now at risk. Easy come, easy go.
This brings us to the concept of the so-called 500-year flood. To statisticians, it’s the flood with a 1- in-500 (0.2 percent) chance of occurring in any given year. To geologists, it’s pure fiction because it requires that an unknown future behaves in a way similar to the recent past, and that a century’s worth of data can be used to extrapolate the next 400 years.
This fiction explains why Houston has experienced three 500-year floods within the last three years. Each is a fairy tale on which federal flood policy has been based. I’m glad the private sector reads non-fiction.