The new face of flooding
Alabama and the U.S. Gulf Coast region have seen a sudden burst of sea level rise, spurring flooding in low areas exacerbated by rainfall and high tides.
THEODORE, Ala.John Corideo drove the solitary two-lane highways of southern Alabama, eyeing the roadside ditches. It had been raining off and on for days and Corideo, chief of the Fowl River Fire District, knew that if it continued, his department could be outmatched by floodwaters.It kept raining. Water filled the ditches and climbed over roads, swallowing parts of a main highway. About 10 residents who needed to be rescued were brought back to the station in firetrucks. More remained stranded in floodwaters, out of the department’s reach. “That week … we just caught hell,” Corideo said.What the residents and rescuers of the Fowl River region faced on that day was part of a dangerous phenomenon reshaping the southern United States: Rapidly rising seas are combining with storms to generate epic floods, threatening lives, property and livelihoods.In the Fowl River’s case, unusually high tides slowed floodwaters as they went downstream to drain. This increased the water’s depth and flooded a wide expanse — even several miles upstream. The result was deluged roads, washed out cars and damaged houses from a flood that was larger, deeper and longer-lasting due to rising seas.These supercharged floods are one of the most pernicious impacts of an unexpected surge in sea levels across the U.S. Gulf and southeast coasts — with the ocean rising an average of 6 inches since 2010, one of the fastest such changes in the world, according to a Washington Post examination of how sea level rise is affecting the region.The Post’s analysis found that sea levels at a tide gauge near the Fowl River rose four times faster in 2010 to 2023 than over the previous four decades.Chart showing sea level rise at Dauphin Island, Alabama. The chart shows the rate of sea level rise from 1980 to 2009 which was 0.1 inches per year, and the rate from 2010 to 2023 which was 0.5 inches per year. The chart also compares these rates to the overall rates in the Gulf of Mexico, which in the former period were slower than and in the latter period were faster than the Gulf.The rapid burst of sea level rise has struck a region spanning from Brownsville, Tex., to Cape Hatteras, N.C., where coastal counties are home to 28 million people. Outdated infrastructure built to manage water, some of it over a century old, cannot keep up. As a result, the seas are swallowing coastal land, damaging property, submerging septic tanks and making key roads increasingly impassable.“Our canary in the coal mine for sea level rise is storm water flooding,” said Renee Collini, director of the Community Resilience Center at the Water Institute. “Each inch up of sea level rise reduces the effectiveness of our storm water to drain and the only place left for it to go is into our roads, yards, homes and businesses.”To explore sea level rise in the region, The Post analyzed trends at federal tide gauges and drew on satellite data to compare the Gulf of Mexico with the rest of the globe. The Post also worked with Bret Webb, a coastal engineer at the University of South Alabama, to closely study the 2023 flood in the Fowl River region. A sophisticated river simulation Webb produced showed how higher seas would have turbocharged the flood, making it worse — with deeper waters covering a larger area for a longer time — than if the same event had occurred in an era of lower seas.These analyses showed how much the ocean is rising and how it’s affecting flooding across this region, a preview of what other parts of the United States and the world that are affected by sea level rise will face in coming decades.Key findingsThe ocean off the U.S. Gulf and Southern Atlantic coasts has, since 2010, risen at about triple the rate experienced during the previous 30 years. In just the Gulf of Mexico, sea levels rose at twice the global rate over the past 14 years.There are now more dangerous rain-driven and flash floods reported within 10 miles of the coast in the region. Their numbers increased by 42 percent from 2007 to 2022 — a total of 2,800 events, according to a Post analysis of National Weather Service data.The Fowl River flood was caused by intense but not record-breaking thunderstorms that collided with high tides, according to Webb’s analysis. Working together, they caused the river to spill miles inland. The higher seas of today, compared with sea levels in 1967, would have increased the volume of the flood by nearly 10 percent of the river in its normal state, the analysis showed.Human-caused climate change is driving an acceleration of sea level rise globally, largely because of the faster melting of the globe’s giant sheets of ice. Scientists do not know for certain why this region is experiencing a surge in sea levels beyond the global average, but one theory is that naturally occurring ocean currents are moving ever-warmer ocean water deep into the Gulf. This warm water expands and causes seas to rise. This comes on top of sinking land, which has long exacerbated sea level rise in the region.“When I first moved here in 2007, the rule of thumb was a foot per century,” said Webb. “Well, looking back now in the last 20 years, we’ve gotten half of that in a fifth of the time.”Press Enter to skip to end of carouselThe Drowning SouthCarousel - $The Drowning South: use tab or arrows to navigateSeas are rising across the South faster than almost anywhere. The Post explores what that means on the ground.End of carouselThe Fowl River region is a quiet inland expanse of flat spaces and pine forests filled with large riverfront homes, more modest dwellings and a few mobile home parks. The wealthier inhabitants live along the wider stretches of the river and near the coast, and lower income residents generally populate rural areas upstream. The community is largely White, and the population swells in the summer, when people come to boat and fish in the river.The rainfall on June 19 was dramatic, but not necessarily record-breaking. And the tide at the end of the Fowl River barely qualified as a NOAA high tide flooding event. But it was the confluence of these factors, Webb said, that made the flood extreme — and highlights a phenomenon that is growing in frequency but has received little attention.Scientists in the United States have mostly focused on this type of collision of precipitation and tides — known as compound events — with hurricanes, not everyday rain events. But more local deluges are now attracting growing scientific attention. Webb’s analysis shows that the sea level acceleration since 2010 was substantial enough to have an impact in the Fowl River flood — a finding that breaks new ground as scientists grapple with rising oceans.A deeper, wider floodTo simulate the flow of the river, Webb used modeling software designed by the federal government. He then drew on three sources of regional data to show how sea level rise made the flood worse.Mapping the areaWebb mapped the river’s channel and the height of the surrounding land, and told the software how the river flows.Map showing elevation data in the area surrounding the Fowl River studied by Bret Webb, emphasizing the area that is below normal high tide.Measuring the river and oceanTo show the effect of rainfall on the river and the height of the ocean, Webb used two sources of data: a river gauge 10 miles upstream and a tide gauge where the river empties into Mobile Bay.Graphic showing river levels at the Fowl River at Half-Mile Road streamgage and sea levels at the tide gauge at East Fowl River Bridge.How deep the water got during the floodRiver levels swelled, filling the waterway as unusually high tides kept the excess rainfall from draining. As a result, the river leaped far beyond its banks.Map showing water depth from Bret Webb's flood modelIn some places, higher sea levels led to deeper floodsThe sea level — which includes both the rise of the ocean and sinking of land — was the analysis’ sole variable. “It’s the only thing that’s changing in the model from scenario to scenario,” Webb said.Map showing the change in depth between the 1967 and 2023 sea level scenarios in Bret Webb's model.The simulations found that last year’s flood would have more than doubled the total volume of water in the river, versus what it holds in normal high tide conditions.Webb ran the model with ocean heights characteristic of the past, including 1967, the first full year of data available, and higher levels projected in the future.He found that the 2023 flood was larger than the simulated 1967 version of the event due to higher sea levels, with most of the increase in floodwaters occurring between 2010 and 2023.Webb also found that last year’s flood would have lasted longer and flooded an additional 43 acres.The real-life flood was likely worse than what the model produced, Webb said, because the model would not have captured the full extent of rainfall or how a higher sea is pushing up the groundwater level, making flooding worse.The simulation does not fully reproduce the events of June 19. Experts who reviewed Webb’s analysis broadly agreed with its finding that today’s sea levels would have caused worse flooding. The main takeaway from the model, they said, was that it showed the impact of sea level rise across the entire flooded area, rather than in specific locations.Most of the individual stories in this story nonetheless took place in areas near the Fowl River where Webb’s model shows sea level rise impacted flooding. In some spots upstream, the model suggests its influence could emerge in the future.Awash in waterCorideo has worked in emergency response for nearly five decades. He was dispatched to Ground Zero on 9/11 while a firefighter in Mastic, N.Y. In 2005, he came to the Gulf Coast with FEMA as part of the emergency response to Hurricane Katrina, and stayed after meeting his wife.Today, Corideo responds to over 1,000 calls a year and operates his department on a $120,000 budget, which pays his salary, fuel and operating costs. He doesn’t have the money to repair the ceiling of the engine bay where the firetrucks park, from which streams of insulation dangle. Corideo’s department mostly scrapes by for house fires, health calls and brushfires — but an extreme flash flood is another matter.John Corideo, fire chief of the Fowl River Volunteer Fire Department, stands in the department's dilapidated engine bay. (Jahi Chikwendiu/The Washington Post)He remembers being “wet for most of the day” on June 19. When he thought his truck might get submerged he got out and waded. Floodwaters are often filled with hazards such as submerged wood and snakes. In this case, T.John Mayhall of Servpro of Mobile County, a cleaning and restoration company, said the waters were also “highly contaminated” due to runoff from agricultural land, chemicals and other substances.But Corideo had no protective equipment.“We’re a poor little fire department,” he said.Corideo had no boat, either, and needed to call in the Mobile Fire-Rescue Department, located about 20 miles to the north, to do the most harrowing work. The department has a team trained in water rescues and used a drone to locate stranded residents, said district chief J.P. Ballard, who led the response.“[The water] was rushing in certain places. It presents its own kind of challenges, you have got to have the right people and the right kind of gear to get into those places,” Ballard said.Two rescuers arrived at Debra Baber’s house by boat around 6 p.m. They navigated up to Baber’s porch while a drone buzzed overhead, steering the boat carefully between two vehicles with little more than their roofs visible.Debra Baber sits on the porch where she was rescued by boat during last year's flood. Baber owns property along the Fowl River that includes her home, a swimming hole and camping site. (Ricky Carioti/The Washington Post)The boat came “right up here to this ramp,” Baber said, gesturing outward from her deck. “I got on it … I said, man, I’m going to have me a drink, for 6 hours, I mean, I’ve been panicking.”The Mobile Fire-Rescue Department was not the only outside assistance Corideo had to call in — the nearby Theodore Dawes Fire Rescue department, Mobile County’s Road and Bridge division and others had to help conduct rescues and keep people off flooded roads.The Post talked to 15 people who experienced the deluge. They boated across fields, streets and front yards located miles inland, drove across flooded roads and rescued neighbors’ belongings that had floated downstream. Again and again, residents said that the storm was extreme, even in a rainy and flood-prone region.Kim Baxter Knight’s house sits nearly 12 feet off the ground on stilts, several hundred feet from the river. It was “unbelievable” how quickly the rains swelled the river and submerged both her cars, ruining them, she said.Knight, who lives with her ailing 77-year-old father and 10 cats, didn’t try to evacuate, but with how quickly the water moved, she didn’t think she could have.“It’s never flooded like that before,” she said. “We get flooded, but not like that.”While her insurance company covered her losses, Knight’s monthly payment more than doubled from $128 to $267.Mobile County spent about $150,000 responding to the flood, including putting up barricades and removing objects like toys and yard furniture from drainage systems, said Sharee Broussard, the county’s director of public affairs and community services. Road flooding was localized, she said, and the ground was heavily saturated from days of heavy rainfall.“The water rose quickly, and it receded quickly,” Broussard said.Mayhall’s company responded to at least a dozen homes after the waters receded. People had to treat or discard belongings or parts of their homes that got wet. The cost to remediate a damaged house started around $12,000, Mayhall said.“There’s no small, insignificant or mildly impactful situation for this, unless the water just barely made its entry,” he said. “If it actually came into the home, it’s going to create a significant impact.”Vanishing islandsWhen it rains hard enough or there’s a very high tide along the Fowl River, Sam St. John’s neighbor calls to let him know that his wharf has gone under. St. John drives down from his main residence in Mobile to lift his boats and secure his property.And over time, he said, it has become harder to find a dry road on his drive down.St. John drove by Baber’s house late in the afternoon of June 19, and saw a white pickup with water nearly up to the steering wheel. He later drove across a flooded Windsor Road.“All the routes were blocked,” said St. John, who founded a Mobile-area computer company in the 1980s and now sits on the board of Mobile Baykeeper, a local environmental group dedicated to preserving the region’s waterways. “Even places that I had never seen flood before.”St. John used to water ski on the river as a teenager in the 1970s and has owned a home in the region for decades. “You were just skiing around islands and spits and you never saw anybody, or any houses or anything,” he remembers. St. John later watched them lose plants, then soil.“I watched those islands disappear, year after year,” he said.Map showing detail of the Fowl River from a declassified spy satellite photo from 1976.Map showing aerial imagery of Fowl River from 2019. In comparison with the same view in 1976, two islands have disappeared and a long spit has shortened.The 1976 image is a declassified photograph taken from a spy satellite and obtained through the U.S. Geological Survey. The 2019 aerial image is from the National Agriculture Imagery Program.On the opposite bank of the river from St. John, Ted Henken watched the June 19 flood while standing knee-deep in water that submerged his dock.Henken’s family began vacationing along the Fowl River long before he and his wife Margaret retired here 11 years ago. Back then, there was an island a little offshore from the land they owned, which the family called Monkey Island. Trees and azaleas grew on it.“The kids used to, in order to be able to swim by themselves without their life jacket, they had to swim from there out to that island,” Henken said, gesturing from his boat as he motored downriver.Monkey Island has been swallowed by the river. Other submerged islands are marked by white poles, which warn boats not to drive over their remnants.Henken spent nearly 40 years working for Chevron and started a side hustle in retirement: He and two of his brothers raise neighbors’ lower “crabbing” docks — where people would once sit and lure crabs with just a net and a chicken bone. The higher tides have gotten so bad that water covers these docks so often that they become slimy and corroded. It takes the brothers two days’ work to lift each one.Henken also monitors the environment of the Fowl River by taking water samples at a calm tributary north of his home and is the host of “AL-MB-86,” the code for a rain gauge in his yard that reports daily data as part of a volunteer observers’ network.Henken’s station reported 10.94 inches of total precipitation on June 19 — high, but not extraordinary for rainy Mobile County. If the reading is correct, it amounts to about a one in 25 year storm event, according to Webb.A worsening problemWebb’s model suggests that events like the one in June will get worse as sea levels increase. By 2050, rising seas would produce a flood 17 percent larger by volume than what would have occurred in 1967; by 2100, that increase would be 44 percent.It also illustrates how places farther upstream, which were marginally affected by sea levels but still flooded last year due to rainfall, may feel the growing effects of the ocean in the coming decades. Heavy rains in many regions — including coastal Alabama — are also expected to get worse due to climate change, exacerbating the potential for extreme events.Broussard said Mobile County is “engaged in planning and implementation” to address the threat of sea level rise. The county “works within its purview to mitigate current issues and plan for the future,” she said. For instance, it funds the Mobile Bay National Estuary Program and helps implement its strategies — which take climate change into account. Last year the county approved a coastal restoration project that will help protect a vital road, the Dauphin Island Causeway, from flooding.At this point, Mobile County is not seeing more road maintenance because of flooding, or worsening storm water effects that it can quantify, Broussard said.Last year’s storm impacted much of Mobile County.David Rice, executive vice president of Master Boat Builders. (Jahi Chikwendiu/The Washington Post)Just outside of Mobile, waters swamped an on-ramp to Interstate 10 from the Mobile Causeway, lined with seafood restaurants. Along the coast at Bayou La Batre, two casino boats broke from their moorings and crashed into the dockside.Master Boat Builders, a family-run business, has been in the same Coden Bayou spot for more than 40 years. The storm shattered a wooden bulkhead, took out electrical equipment and caused part of the shipyard to go underwater, forcing the company to stop work for the day, said David Rice, the company’s executive vice president for corporate resources.Master Boat Builders is one of the area’s largest employers and just manufactured the first electric tugboat in the United States, powered by at least 1,100 batteries. The ship, the eWolf, was delivered to the Port of San Diego earlier this year and has just begun operations.Rice said part of the shipyard now floods during major high tides, something that never used to happen. When it does, the company moves workers out of that location and onto a different project until the seas relent. From his home on Dauphin Island, Rice said he’s seen the arrival of much higher tides.“I really don’t think people think about it,” Rice said. “They see it on TV and I think it’s some kind of liberal hoax. But it’s not. If you live on the water, you’re on the water, you can see that it’s actually justified.”Shipbuilders construct tug boats at the mouth of Coden Bayou in Bayou La Batre, Ala. (Jahi Chikwendiu/The Washington Post)About this storyBrady Dennis contributed to this report.Design and development by Emily Wright.Photo editing by Sandra M. Stevenson and Amanda Voisard. Video editing by John Farrell. Design editing by Joseph Moore.Editing by Katie Zezima, Monica Ulmanu and Anu Narayanswamy. Additional editing by Juliet Eilperin. Project editing by KC Schaper. Copy editing by Gaby Morera Di Núbila.Additional support from Jordan Melendrez, Erica Snow, Kathleen Floyd, Victoria Rossi and Ana Carano.MethodologyThe Washington Post used monthly tide gauge data from 127 gauges from the National Oceanic and Atmospheric Administration for relative mean sea levels in the United States. This is adjusted for seasonal signals for ocean temperature, currents and other marine and atmospheric variables.For its analysis The Post relied on dozens of tide gauges along the coasts of the United States, measurements which are affected both by the rising ocean and slow but persistent movement of land. It also took into account satellite data for global sea level rise, which measures ocean heights independent of land movement.Annual means for two time periods — 1980 to 2009 and 2010 through 2023 — were calculated. Only gauges which had at least eight months of data for a given year and 70 percent of the years were used. Three gauges used in this analysis are not currently in service but had sufficient data for the 1980 to 2023 time period to include in the analysis.A linear regression model was applied to the annual means for each gauge to determine the trends for each time period and calculate an annual rate of relative mean sea level rise. Because readings from tide gauges are also influenced by the rising or sinking of land, these findings are referred to as changes in relative mean sea level.To analyze changes in sea level around the globe, The Post used data based on satellite altimetry readings produced by NOAA. Annual means were calculated for 1993 through 2023 for the global data and for each ocean. The Post applied a linear regression model estimating the annual rates of change in mean sea level for each ocean and the global average. The data from the satellite altimeters are measures of ocean height independent of any land movement, or absolute means.Scientists, including Jianjun Yin and Sönke Dangendorf, have studied regional trends in sea level rise. The Post’s analysis builds on this body of work and compares trends for the 2010-2023 and 1980-2009 time periods to drive home the rate of acceleration in recent years. The Post also presents the trends for each tide gauge included.Flood eventsTo examine trends in reported flood events along the Gulf and Southeast Atlantic Coasts of the United States, The Post relied on the Storm Events Database compiled by the National Weather Service and maintained by the National Centers for Environmental Information. After consulting with data experts from the NWS and NCEI, The Post used the events data from 2007 to 2022 since reporting and data maintenance practices had been standardized by late 2006.The Post examined and geolocated all events classified as “flood” or “flash flood” for eight states: Texas, Louisiana, Mississippi, Alabama, Florida, Georgia, South Carolina and North Carolina, removing events related to hurricanes and tropical storms. A shoreline shapefile from NOAA was used to calculate the distance to the coast for each event, focusing on events within 10 miles of the coast for the analysis.The simulation of the Fowl River floodFor the simulation of the Fowl River flood, The Post worked with an outside expert, Bret Webb. He assembled key data elements around elevation and tide levels from the two closest federal tide gauges.Webb fed the elevation data to the Sedimentation and River Hydraulics — Two-Dimensional model (SRH-2D model), a hydraulic model developed at the U.S. Bureau of Reclamation. Webb used the Surface-water Modeling System (SMS) software to deploy the model.Reporters from the Post also provided Webb with locations and details about how high the water was, which was used to tune the model.Webb developed six scenarios to test the impacts of different sea levels on the flood. The first is the baseline flood, using the data from June 18-21. Then, Webb changed the mean sea level variable at the mouth of the river to simulate the extent of the flood based on lower ocean levels from 1967, 1990 and 2010. Webb also projected sea levels forward to 2050 and 2100. For each scenario, the model produced time and spatially varying velocity (speed and direction), water depth and water surface elevation for the duration of the simulation.The Post showed Webb’s work to sea level rise experts who backed the analysis and findings. Reviewers included:Christopher Piecuch, a sea level scientist at Woods Hole Oceanographic InstitutionThomas Wahl, an expert on compound events at the University of Central FloridaRenee Collini, director of the Community Resilience Center at the Water Institute.The reviewers generally described Webb’s analysis as a thorough look at a single event, and said that it captured the likely role of sea level rise in making that event worse. They cautioned that while the research shows the broad impact of sea level rise on rain driven flooding in the Fowl River event, it is less reliable for inferring the exact flooding risk, or exact role of sea level rise, in a specific location.Click here for a detailed explanation of Webb’s work.
