Lawmakers in some states have blithely dismissed the threats of global warming, most notably those in North Carolina, where state lawmakers earlier this year passed a law ordering that only historic trends, not projections, be considered in coastal planning.
In South Florida, political leaders and planners arent in denial. In 2009, Miami-Dade, Broward, Palm Beach and Monroe counties formed a climate change compact to work together to confront a problem South Florida will see sooner than just about anywhere.
A string of studies by insurers, environmental groups and government and university researchers have singled out Miami-Dade County at the top of the list of at-risk cities, with tens of billions of dollars of property that could be damaged by heightened storm surge or flooding.
Earlier this year, a report from Climate Central, an independent research and journalism organization, suggested Miami-Dade and Broward counties alone have more people vulnerable to flooding than any state except Florida and Louisiana. Other studies suggest some of the lowest-lying Florida Keys may be the first to be inundated.
The compacts draft projection of sea level in Southeast Florida based on local trends and global forecasts calls for a rise of three to seven inches by 2030 and nine to 24 inches by 2060. From there, many scientists predict the trend could accelerate.
Miami Beach and other low-lying barrier islands are particularly vulnerable to drainage problems but those are spreading to the mainland, said FAUs Heimlich. The FAU study found a sea level rise of about six inches could cut flood-control capacity by more than half with higher tides bottling up canals and structures that now drain with gravity as runoff flows downhill to the coast.
This is a problem that is not far away, said Heimlich. It is already being experienced and will get worse in the next few years.
Broward and Miami-Dade counties both are doing more detailed analysis of how existing drainage systems might have to be retro-fitted or expanded.
Doug Yoder, deputy director of the Miami-Dade Water and Sewer Department, said sea level rise will also push more salty and brackish water into surface drainage and sewer systems, adding to the costs and volume of treating runoff. Worsening salt water intrusion, which can shrink and taint the underground Biscayne Aquifer, the countys main source of drinking water, will also require more expensive treatment systems in the future.
Potentially, Yoder said, the county could have to move sewage treatment plants like the aging facility on Virginia Key inland and build them at higher elevations. Monroe County is already planning to do that with a new fire station in Key West, adding several feet to the ground-floor elevation.
While there are a wide range of potential costs, including raising roads, Yoder said solving drainage was critical. Without it, he said, you wonder how long people will continue to live in a place that floods routinely.
James Murley, executive director of the South Florida Regional Planning Council, said Miami Beach is out front in accounting for sea level rise. On-going budget challenges could make it tough sell for some communities worried about spending too much to address impacts that might not come as soon as anticipated. Forecasts differ on the pace and impact.