In 2017, the powerful Hurricane Irma flanked Miami-Dade and the rest of South Florida.
Across much of the region, a Category 4 storm eye hit the Florida Keys a few miles away, and the impact of a tropical storm was felt at best. It was bad enough: Wind and rain damaged roofs, cut down trees and power lines, and power was out for days – most notoriously, 12 elderly people in Broward County ended up in nursing homes without power.
However, along the coastline of Biscayne Bay, Irma had winds equivalent to a Category 1 hurricane — strong enough to send 3 feet to over 6 feet of water washing over several blocks in the Miami Brickell and Coconut Grove areas, destroying piers, docks and boats, flooding streets for days flooded with the Biscay Sea and shells, and stockpiled sailboats and other boats along the shores of houses and yards on South Bay Boulevard and in the bay.
Channels that normally drain into the bay flow back as the tide moves inland, overflowing into communities, streets and homes.
The damage caused by the fast-moving walls of the bay, while limited in scope and scope, in many cases took years and millions of dollars to repair.
However, if the storm were the same size and strength as Hurricane Yang, it would push a storm surge of at least 15 feet onto the shores of Fort Myers Beach, directly hitting Key Biscayne and the populous centers occupying the barrier islands that protect it. These include Biscayne Bay, Miami Beach, and the beach towns stretching several miles north along a series of problematic fortified barrier islands.
Experts point out that public concern about hurricanes is largely focused on wind damage. But a large, slow Category 4 storm like Hurricane Yan will cause catastrophic surges along much of the Miami-Dade coastline and further inland than Hurricane Center Irma’s surge risk map shows.
Many experts say Miami-Dade remains unprepared in many ways, both mentally and physically, as we continue to grow residents and address ocean and groundwater vulnerabilities from Miami Beach to Brickell and South Miami-Dade. The groundwater level has risen due to climate change.
Government officials in counties and vulnerable cities are well aware of these risks. Building codes already require new residential and commercial buildings in areas most vulnerable to surge waves to be elevated so that water can pass through them without damaging them. Miami Beach and Biscayne Bay have spent millions of dollars with federal assistance to restore dune defenses and improve beaches along the Atlantic coast. Authorities are working on new, nature-inspired ways to reduce the force of storm surges, from offshore artificial reefs to new mangrove islands and “living coastlines” along the bay.
But even the best solutions will at best lessen rather than stop the effects of severe storm surges. Many of them are far away. However, they could only win about 30 years before rising sea levels destroyed the fortifications again. Meanwhile, thousands of old houses and buildings on the ground remain extremely vulnerable to power surges.
“What you’re seeing in southwest Florida has made us very concerned about our vulnerability and what we need to do,” said Roland Samimi, chief recovery officer for the village of Biscayne Bay, which is just 3. 4 feet above sea level. for voters. $100 million in funding streams approved to support major resilience projects.
“You can only protect yourself from the wave. There will always be an impact. You will never eliminate it. You can’t beat the wave.”
When this violent storm hits Biscayne Bay sometime in the future, rough waters will rise from a higher starting point: according to NOAA tidal measurements, local sea levels have risen by more than 100 percent since 1950. It has risen by 8 inches and is expected to will rise. by 16 to 32 inches by 2070, according to the Southeast Florida Regional Climate Change Agreement.
Experts say the sheer weight and force of fast currents and rough waves can damage buildings, bridges, power grids and other public infrastructure more than wind, rain and flooding in vulnerable areas of Miami-Dade. Water, not wind, is the cause of most hurricane deaths. This is exactly what happened when Hurricane Ian blew massive amounts of water onto the beaches of Captiva and Fort Myers in southwest Florida, and in some cases onto houses, bridges and other structures on the two barrier islands. 120 people, most of them drowned.
“Moving water has tremendous power and is what causes most of the damage,” said Dennis Hector, a University of Miami professor of architecture and an expert in hurricane mitigation and structural restoration.
Maps from the Hurricane Center show that the Miami area is more prone to surges than the Fort Myers area, and more so than northern seaside cities like Fort Lauderdale or Palm Beach. This is because the water in Biscayne Bay is relatively shallow and can fill like a bathtub and overflow violently for many miles inland, across Biscayne Bay and the back of the beach.
The average depth of the bay is less than six feet. The shallow bottom of Biscayne Bay caused the water to accumulate and rise on its own when a strong hurricane washed the water ashore. Low-lying communities 35 miles from the bay, including Homestead, Cutler Bay, Palmetto Bay, Pinecrest, Coconut Grove, and Gables by the Sea, are vulnerable to some of the worst flooding in South Florida.
Penny Tannenbaum was relatively lucky when Irma hit the coast at Coconut Grove: she evacuated, and her house on Fairhaven Place, Bay Street on the canal, was only a few feet from the floodwaters. But when she got home, there was a foot of standing water inside. Its floors, walls, furniture and cabinets were destroyed.
The stench—a mixture of musty silt and effluent sludge—was unbearable. The maintenance contractor she hired entered the house wearing a gas mask. The surrounding streets were covered with a slimy layer of dirt.
“It was like you had to shovel snow, only it was heavy brown mud,” Tannenbaum recalls.
Overall, the hurricane caused approximately $300,000 in damage to Tannenbaum’s home and property and kept her out of the house for 11 months.
The National Hurricane Center’s forecast for Yan called for significant surges along the South Miami-Dade route just before the storm’s path turned north from South Florida.
“Dadeland has water all the way to US 1 and beyond,” said Brian House, chair of the marine sciences department at the Johnston School of Oceanographic and Atmospheric Sciences. Rosenthal at the University of Michigan, who runs the storm surge modeling laboratory. “That’s a good indication of how vulnerable we are.”
If Irma had not changed course as well, her impact on Miami-Dade would have been several times worse, forecasts suggest.
On September 7, 2017, three days before Irma arrived in Florida, the National Hurricane Center predicted that a Category 4 hurricane would make landfall south of Miami before turning north and sweeping the state’s east coast.
If Irma had stayed on this path, barrier islands like Miami Beach and Key Biscayne would have been completely submerged at the height of the storm. In South Dade, floodwaters will inundate every inch of Homestead, Cutler Bay and Palmetto Bay east of the US. 1, and eventually crosses the highway into the lowlands to the west, which can take days or weeks to dry out. The Miami River and numerous canals in South Florida act as a system of waterways providing multiple pathways for water to penetrate inland.
It happened before. Twice in the past century, Miami-Dade has seen storm surges as intense as Jan’s on the Gulf Coast.
Prior to Hurricane Andrew in 1992, the South Florida storm surge record was held by the unnamed Miami hurricane of 1926, which pushed 15 feet of water onto the banks of coconut groves. The storm also washed eight to nine feet of water down Miami Beach. An official memo from the Miami Weather Service office documents the extent of the damage.
“Miami Beach was completely flooded, and at high tide the ocean extended to Miami,” wrote bureau chief Richard Gray in 1926. “All the streets of Miami Beach near the ocean were covered with sand to a depth of several feet, and in some places the cars were completely buried. A few days after the storm, a car was dug out of the sand, inside which was a man, his wife and the bodies of two children” .
Hurricane Andrew, a Category 5 storm and one of the strongest ever to hit the continental United States, broke the 1926 record. At the height of the flood, the water level reached almost 17 feet above normal sea level, as measured by the layer of mud deposited on the walls of the second floor of the old Burger King headquarters, now located in Palmetto Bay. The wave destroyed a timber-framed mansion on the nearby Dearing estate and left a 105-foot research vessel in the mansion’s backyard off Old Cutler Drive.
However, Andrey was a compact storm. The range of bursts it generates, while strong, is severely limited.
Since then, population and housing have increased dramatically in some of the most vulnerable areas. Over the past 20 years, development has created thousands of new apartments, apartments in the flood-prone communities of Edgewater and Brickell Miami, the flood-prone suburbs of Coral Gables and Cutler Bay, and Miami Beach and Sunshine Banks and House Islands Beach. .
In Brickell alone, the flood of new high-rise buildings has increased the total population from nearly 55,000 in 2010 to 68,716 in the 2020 census. Census data shows that zip code 33131, one of three zip codes covering Brickell, has quadrupled in housing units between 2000 and 2020.
In Biscayne Bay, the number of year-round residents has increased from 10,500 in 2000 to 14,800 in 2020, and the number of housing units has increased from 4,240 to 6,929. canals, with the population increasing from 7,000 to 49,250 during the same period. Since 2010, Cutler Bay has welcomed about 5,000 residents and today has a population of over 45,000.
In Miami Beach and the cities extending north to Sunny Isles Beach and Gold Beach, population remained stable throughout the year as many part-time workers bought new high-rise buildings, but the number of housing units after 2000 The population according to the 2020 census is 105,000 people.
All of them are under the threat of a strong surge and were evacuated during a severe storm. But experts fear that some may not fully grasp the threat posed by the surge or understand the nuances of the forecast data. With many residents staying at home as the hurricane rapidly intensified and leaned south before making landfall, confusion or misinterpretation of Yang’s changing projected trajectory could delay Lee County evacuation orders and keep the death toll high.
UM’s House noted that changes in the storm’s paths of just a few miles could make the difference between a devastating storm surge like the one seen in Fort Myers and minimal damage. Hurricane Andrew turned around at the last minute and trapped many people at home in its impact zone.
“Ian is a great example,” House said. “If it moves anywhere close to forecast two days from now, even 10 miles north, Port Charlotte will experience a more catastrophic surge than Fort Myers Beach.”
In class, he said, “Follow the evacuation orders. Don’t assume that the forecast will be perfect. Think of the worst. If it doesn’t, rejoice.”
A number of factors, including the local topography and direction of a storm, wind speed and the magnitude of the wind field, can affect how hard and where it pushes water, House said.
East Florida is slightly less likely to experience a catastrophic storm surge than western Florida.
The west coast of Florida is surrounded by a 150 mile wide shallow ridge known as the West Florida Shelf. As in Biscayne Bay, all the shallow waters along the Gulf Coast contribute to the growth of storm surges. On the east coast, by contrast, the continental shelf extends only about a mile from the coast at its narrowest point near the border of Broward and Palm Beach counties.
This means that the deeper waters of Biscayne Bay and the beaches can absorb more water caused by hurricanes, so they don’t add as much.
However, according to the National Hurricane Center’s Storm Surge Risk Map, tide risk in excess of 9 feet during a Category 4 storm will occur over much of the South Miami-Dade continental coastline in Biscayne Bay, at points along the Miami River, and in various areas . canals, as well as the back of barrier islands such as Biscayne Bay and beaches. In fact, Miami Beach is lower than the waterfront, making it more vulnerable to waves as you move across the bay.
Splash maps from the Hurricane Center show that a Category 4 storm will send massive waves many miles inland in some areas. Rough waters can flood the east side of the coast of Miami and the Upper East Side of Miami, extend beyond the Miami River all the way to Hialeah, flood the village of Coral Gables east of Old Cutler Road with more than 9 feet of water, flood Pinecrest and invade Homes on Miami farm in the east.
Village planners said Hurricane Yan actually brought potential danger to Biscayne Bay residents, but the storm left the central coast east of Orlando, Florida a few days later. A week later, the disrupted weather pattern he left behind sent a “freight train” to the beach in Biscayne Bay, which was badly damaged, village planning director Jeremy Kaleros-Gogh said. The waves tossed massive amounts of sand across the dunes, which restored calming storm surges, and onto the edges of coastal parks and properties.
“On Biscayne Beach, people are surfing like you’ve never seen before,” Calleros-Goger said.
Samimi village resiliency officer added: “The beach has suffered. Residents can see this clearly. People see it. It’s not theoretical.”
However, experts say that even the best regulations, engineering and natural remedies cannot eliminate the risks to people’s lives if people don’t take it seriously. They are concerned that many of the locals have long forgotten Andrew’s lessons, even though thousands of newcomers have never encountered any tropical storm. They fear that many will ignore evacuation orders that will require thousands of people to leave their homes during a major storm.
Miami-Dade Mayor Daniella Levine Cava said she is confident the county’s early warning system won’t get anyone in trouble when a major storm threatens to hit. She noted that surge zones for the system have been clearly marked and the county is providing assistance in the form of a circulating shuttle that takes residents to shelters.
Post time: Nov-10-2022