Return of the King Tide: Miami Beach Braces for Tidal Flooding

The annual "King Tide," the year's highest astronomical tide, will make a return to coastal cities Thursday, which has Miami Beach city officials working against the clock to safeguard their streets against tidal flooding.

"The City of Miami Beach has placed check valves in over 50 critical outfalls that allow tidal flooding in the city," City Engineer Bruce A. Mowry said in an email. "We are checking daily to see if additional locations can be identified."

The check valves will allow an outflow of storm water to be drained, but will inhibit reverse flow inland.

Residents are encouraged to utilize online resources to report flooding in the region, according to reports from the city's Twitter account.

Through an app, anyone can submit their flooding reports and photographs to identify potential hazards caused by the tides.

The 2013 King Tide resulted in roadway flooding across Miami Beach, a city of 91,000 people, but since then, new storm water management systems have been constructed and put into place.

"The 'King Tide' is an informal term given to very high tides anywhere," according to Brian McNoldy, a senior research associate at the University of Miami's Rosenstiel School of Marine and Atmospheric Science.

"It's just an alignment of the moon and sun that tugs our ocean farther away [or] toward the surface than normal," he said, adding this causes very high or very low tides.

The tides can be more extreme than average because of the alignment of the sun, Earth and moon, he said.

The proximity of the moon to Earth (perigee), and the proximity of the Earth to the sun (perihelion) impacts the tides.

"It's not just one exact moment; the King Tides last for days as the alignment comes into focus and out of focus."

Astronomically higher-than-average tides happen everywhere on Earth and are very predictable, he added.

While tides will remain at their highest from Oct. 9 through Oct. 10, tides this week have already been above their predicted normal, according to NOAA reports, which could make the impacts worse than expected, AccuWeather.com Meteorologist Jesse Ferrell said.

"They don't happen at the same time everywhere on Earth," McNoldy said. "Some are spring-fall, some are winter-summer. In much of the eastern U.S., the spring-fall full moon is most conducive to extreme tidal fluctuations."

Estimates of this year's King Tide in Florida are around four feet, according to the Miami Herald.

"Several months ago, the city approved emergency construction of several storm water pump stations in critical areas of South Beach," Mowry said, adding that six pumps are currently in service.

"Sizes of the storm water pump stations vary in size, but a typical pump size range is 7,000 to 14,000 gallons per minute for each pump," Mowry said. Stations usually have two pumps.

In addition to the check valves and storm water pump stations draining the water into Biscayne Bay, several large trailer-mounted pumps are also available to city officials and can be moved to any location that may be required over the next couple of weeks, Mowry added.

"The storm water pumps either lift the water to a higher elevation so it flows to the Bay or pressures water in the outfall to the Bay," he said.

As sea levels continue to rise and challenge the area's infrastructure, Miami Beach officials implemented a sea-level rise and storm water mitigation program costing an estimated $300 million.

"Higher tides are projected to continue for years and the city is preparing for the future," he said.

"There are plenty of coastal cities around the world at great risk from sea-level rise in the coming decades, but southern Florida is very flat and sits upon porous limestone," McNoldy said. "So, in addition to flood waters coming at us from the sides, it's also already causing problems from below."

The five-year program will develop infrastructure to manage the storm water issues facing the city. With the ongoing project, the estimated number of pump stations for Miami Beach will be approximately 50 to 60 new pump stations, Mowry added.

"We will have four more storm water pump stations placed in service over the next six months in the South Beach area," he said.

"The flooding potential certainly increases as sea level rises," McNoldy said. "Instead of the water level being 3.1 inches on a street somewhere, it could be 3.5 inches for example. Just add the amount of sea-level rise to whatever the astronomical tide is generating. But in flat areas, an inch or two in vertical elevation can extend several yards or more in the horizontal. It could make the difference between being completely dry and having some standing water."

McNoldy said the infrastructure being constructed by the city of Miami Beach can help reduce tidal flooding now, but will not provide an overall solution to rising sea levels threatening the area.

"It does seem that the new infrastructure will be somewhat effective in reducing the routine flooding in Miami Beach," he said. "But it is more of a patch than a solution."