Communities Under Water: Lessons Learned from Extreme Floods
VOLUME 29, NUMBER 4, FALL 2016
Coastal Heritage is a quarterly publication of the S.C. Sea Grant Consortium, a science-based state agency supporting research, education, and outreach to conserve coastal resources and enhance economic opportunity for the people of South Carolina.
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S.C. Floods 2015-16: Lessons Learned
Communities Under Water: Lessons Learned from Extreme Floods
By Joey Holleman
• Flood insurance: Because “we all live in a flood plain”
• Storm surge: “Powerful is an understatement”
• Reading and Websites
• News and Notes
From narrow neighborhood ditches to major rivers, nearly every waterway in wide swaths of South Carolina swelled to extreme levels during and after a record-breaking rainfall in early October 2015. “It’s never flooded like that around here” seemed like the new state motto. The tendency might have been to view the resulting flood and its $2 billion in damages as a once-in-a-lifetime disaster and not let it remarkably change the way we work, live, play, and plan.
Then Hurricane Matthew churned up the coast in October 2016, dumping slightly less rainfall but enough to cause another major flooding event in coastal South Carolina. The new motto this time could have been: “Not again!” In the extreme northeast corner of the state, Matthew flooding was even worse than in October 2015, thus driving home
First, these types of extraordinary meteorological and hydro-logical events are growing more common. The amount of precipitation in the most powerful storms in the Southeast increased by 27 percent from 1958 through 2012, according to a report from the National Science and Technology Council. The phenomena, coined “rain bombs,” make scientific sense: Global temperatures have been on the rise, and warmer air holds more water vapor than cooler air. Those skeptical of statistics and studies need only pay attention to news reports. Before the end of October 2015, the South Carolina flood had faded in national memory behind two deadly floods a week apart in Texas. Additional record-breaking deluges hit Arkansas, West Virginia, Maryland, and Louisiana before Matthew gave South Carolina another thorough drenching.
And secondly, 500-year floods, a misunderstood term based on statistics, don’t happen just once every five centuries. The laws of probability don’t work that way. Instead, the term refers to a 0.2 percent chance of one of those events occurring during any year. While South Carolina didn’t get 500-year floods in back-to-back years in exactly the same location, Matthew pushed the Little Pee Dee River to 500-year levels at Galivants Ferry in 2016, which is about 50 miles from where the Black River hit 500-year levels in Kingstree in 2015.
Both of those points stress the need for all of us to learn from our flooding experiences. Using that knowledge to prepare people, homes, and infrastructure to better handle the next major flood builds community resilience.
“It amazes me that people haven’t thought more about resilience,” says Gerald Galloway, a University of Maryland engineering professor whose research focuses on flood resilience and mitigation. Galloway made that comment at a February 2016 symposium organized by the Charleston Resilience Network (CRN), a relatively new group of public and private stakeholders, including the S.C. Sea Grant Consortium. The CRN was formed to help communities prepare for and deal with events such as the October 2015 floods.
According to the Federal Emergency Management Agency (FEMA), flooding accounts for 85 percent of all disaster declarations in the United States. Flooding caused $260 billion in damages from 1980 through 2013. Improved community resilience won’t stop flooding, but it could reduce the impact.
“Resilience is where it’s at,” Galloway says. “What are we doing to make us better the next time around? We can’t afford $6 billion in flood losses in this country every year.”
October 2015: Atmospheric flood recipe
South Carolina was bone dry in early August 2015, with crops dying in fields and many waterways running at 10 percent of their normal flow. Farmers and gardeners welcomed a couple of quenching rains in August and September, but the state’s streams still were very low. Then in early October, while most people were paying attention to strengthening Hurricane Joaquin in the Atlantic, a separate low-pressure system stalled over southern Georgia.
The land-based low plopped down in an ideal location for its counterclockwise rotation to pull moist air up from the tropics. When that saturated air lifted over the low’s stalled frontal boundary, rain poured down on South Carolina. The first round of rain had little to do with Joaquin, but moisture in the outer bands of the hurricane likely fed into later rounds, says Ron Morales, warning coordination meteorologist with the National Weather Service (NWS) in Charleston.
NWS forecast models recognized the flood potential early, warning on October 1 that Charleston should expect more than 10 inches of rain over the next four days. “Everyone was worried about Joaquin,” Morales says. “We were trying to get people to stop looking at Joaquin and look at this rain forecast.”
Heavy rain started in Charleston on the afternoon of October 1. Then it stopped late on October 2. Hope Mizzell, state climatologist with the S.C. Department of Natural Resources (SCDNR), heard from skeptics when the first blast of rain ended. She begged them not to take the forecast lightly.
“With each forecast, it became more clear somewhere was going to get it,” Mizzell says. “You didn’t know precisely where the maximum amount would fall, but you knew there was a high likelihood it would happen somewhere. After it slowed down, I told people who were contacting me, ‘Do not even think this is over!’ ”
It wasn’t. The atmospheric fire hose opened full throttle over Charleston during late afternoon October 3, pushing into the central part of the state and the northern coast overnight. By the time skies cleared on October 5, one-third of
the area’s average annual precipitation had been crammed into four days in coastal and inland communities from Charleston north to Myrtle Beach. One site in Mount Pleasant registered 26.88 inches. Four-day totals included 24.75 inches in Williamsburg County, 23.74 inches in Horry County, and 22.02 inches in Berkeley County.
Flood records were set on the Black River at Kingstree, Black Creek near Quinby in Florence County, and on Gills Creek, Smith Branch, and Pen Branch in Columbia. It’s impossible to accurately determine the peak at Gills Creek. The deluge washed away the gauge.
The force of flowing water buckled roads and tested the strength of dams. The official tallies from a state infrastructure damage report: 541 roads and 221 bridges closed; 52 state-regulated dams and another 191 smaller dams damaged. Most of the dams simply overtopped and suffered erosion, but several in the Gills Creek watershed failed, cascading massive pulses of water through suburban Columbia neighborhoods that never had flooded before.
In the lowcountry, high water forced the closure of sections of U.S. 17 both north and south of Charleston. Main Road, the major connection from U.S. 17 to Johns Island and Kiawah Island, was shut down for days. Further inland, portions of I-95 also had to be closed.
The rising water didn’t play favorites, enveloping high-end mansions and mobile home parks. State officials say 33,100 homes had more than a foot of water in them at some point during the resultant flooding, which continued for two weeks as water moved downstream. Thousands of people had to be plucked from homes by rescuers in boats. Officially, 19 deaths were linked to the 2015 flood, with three of those in coastal counties. The majority of deaths occurred when people drove into flooded roadways. The overriding lesson: Don’t drive into water—turn around, don’t drown.
Many people whose homes were impacted by the rising waters now say they fanatically check weather forecasts. Mizzell hopes that is another lesson learned from October 2015: Pay attention to forecasts and don’t assume you are safe.
“It had been so long since we had experienced a flood,” Mizzell says. “You knew everybody’s response would be, ‘It won’t be a problem in my neighborhood.’ People who have lived in their home 20 years and it’s never flooded think they’re not in a flood zone. Twenty years is a very small climatological footprint. Next time, people will recognize that we are vulnerable.”
When the “next time” came just a year later, people did pay attention. State officials estimated 350,000 fled the coast after Governor Nikki Haley ordered an evacuation ahead of Hurricane Matthew. Even with powerful winds and storm surge, Hurricane Matthew caused five deaths compared to 19 during the 2015 flooding.
Flood hits on a personal level
On the night of October 3, 2015, Milton Green, like many in South Carolina, was entranced as the Clemson-Notre Dame football game came down to a final drive. He also was aware of dire rainfall predictions. Throughout the game, he got up from his recliner during commercial breaks to check on water rising slowly across his backyard in North Charleston’s Pepperhill subdivision. The frantic
last few minutes of the game stole his attention away from his flood checks. When the Clemson Tigers finally closed out the victory, he says, “I put down the footrest on my recliner, and my feet went ‘squish’.” The carpet in his low-lying living room was soaked.
Green hustled his wife and granddaughter out of the higher section of the house and drove out of the neighborhood as quickly as possible. Good thing he did. “When I came back the next day, the water was so deep I had to reach down into the water to put the key into the front-door lock,” he says.
Green moved into the house in 1989, and he says it never had flooded before. But water from neighboring wetlands had been slowly creeping higher in his yard after each heavy rain for about a decade. He speculates the change is related to construction during that period of the nearby Palmetto Commerce Parkway.
Hydrology studies required for the parkway indicated the road should create little additional runoff into the wetlands behind Pepperhill. The study estimated the parkway would add 36.2 acres of impervious surface—or hard surface that doesn’t soak up rainfall—to the 4,400-acre drainage area. The ditch system leading to the neighboring Bluehouse Swamp area was estimated to easily handle 4,600 cubic feet per second (cfs) of runoff in a 100-year rain event. The new road
was estimated to add 100 cfs, and the additional flow enters the system downstream from Pepperhill.
Of course, the parkway’s road surface is far from the only new construction in the area. Businesses have popped up along the parkway, and hundreds of homes have been built to the west, or upstream, of Pepperhill
in the past 20 years. Regardless of the source, something is causing ditches around Pepperhill to back up with water quicker than they did several years ago, even during summer thunderstorms. North Charleston officials want a more comprehensive study of the wetlands, ditches, and creeks that flow beside Pepperhill and the nearby Northwoods Estates subdivisions. They have applied for a FEMA mitigation grant to pay for the study.
Pepperhill homeowners were more than a little frustrated that they flooded again during Hurricane Matthew before the watershed study was done. Green, who evacuated before Matthew, returned to find 10-15 inches of water in his house. He had spent $60,000 getting it back in good shape after October 2015, much of that from a Small Business Administration loan. Now, he needs to start all over with the stripping of floors and sheetrock to prevent mold problems. The only mild solace: He learned one important lesson in October 2015
and bought flood insurance between the two events, so most of the repair costs won’t come out of his pocket this time around.
Green would gladly take a buyout offer for his house. “The only thing they can do is get us out of here now,” he says, “because the next flood is going to do the same thing.”
After the 2015 floods, North Charleston requested FEMA flood recovery money that could be used to buy and demolish up to nine homes that have flooded multiple times on New Ryder Road in Northwoods Estates. Funds and approval from FEMA hadn’t come through by October 2016, and those homes flooded again. The homes that flooded in Pepperhill in 2015 weren’t eligible for that round of buyouts because
they weren’t considered repetitive loss properties. They might be eligible if FEMA designates buyout funds for Matthew flood victims.
In 2015, there were 1,508 homes statewide considered repetitive loss properties, up from 1,131 in 1998 before Hurricane Floyd, according to FEMA. The number most likely will go up due to Hurricane Matthew.
In addition to seeking funds for a watershed study for the Bluehouse Swamp area, North Charleston officials have discussed strengthening building codes. The city already requires a one-foot freeboard, or bottom floors one foot above 100-year flood level, in new construction. The city of Conway enacted a two-foot freeboard after Hurricane Floyd flooding in 1999. A recent federal mandate requires all buildings constructed with federal funds have at least a two-foot freeboard, and all critical infrastructure must have a three-foot freeboard. Those types of flood resilience steps could be an important effect of the 2015 and 2016 flooding, experts say.
Solutions can be complex, costly
Charleston has more experience with flooding than most communities in South Carolina. A big chunk of the peninsula’s infrastructure has been built on top of filled-in tidal creeks, which routinely are the first places to flood during extreme tides or heavy rain. Charleston city leaders have put resilience in the forefront. The city came up with a comprehensive sea-level rise strategy, with nearly 80 recommended initiatives based on sea level rising 1.5 to 2.5 feet in 50 years.
City leaders in recent years have approved two property tax increases and a stormwater utility fee. The city has spent, or plans to spend, $235 million on stormwater improvement projects from 1990-2020.
The work involves digging shafts down more than 100 feet, carving horizontal tunnels, and installing pumps to move water away from problem areas. One section, on Calhoun Street from East Bay to Meeting streets, was completed in 2001. Another in the Market Street area was mostly finished by October 2015. Flooding in those areas in October 2015 was minimal, but storm surge during Hurricane Matthew backed up several feet deep in the
The worst flooding in Charleston’s city limits in 2015 wasn’t on the peninsula; it was in suburban neighborhoods west of the Ashley River. “When it floods there, it floods from thunderstorms,” says Laura Cabiness, director of the city’s Department of Public Service. “Those thunderstorms can happen two or three times a year, and they’re very tricky to predict. With a hurricane, we have time to evacuate people. With these thunderstorms, we don’t have much time. So now, in addition to watching sea-level rise and storm surge, we’re watching these rainfall events.”
Charleston was aware of the potential for flooding in the suburbs. The first of the city’s stormwater improvement projects in the 1990s was in the Ardmore area of West Ashley. Also, homes in sections of the Shadowmoss Plantation subdivision have flooded multiple times in recent decades. A complex of townhomes flooded for the first time in 1986. Then new homes constructed in a section along Bees Ferry Road flooded multiple times in the 1990s.
This prompted the city and Charleston County to fund a project that installed three new 72-inch -culverts through a nearby railroad berm in 1997. When those homes flooded again, the city knew something was going on in the Church Creek basin that drains Shadowmoss and surrounding communities.
“The homes that flooded weren’t in the FEMA flood zone,” Cabiness says. “We did a mapping study, and the FEMA flood maps were just downright wrong when those areas were developed.”
It appeared, Cabiness says, the flood maps were influenced more by storm surge than by rainfall. The potential blocking effect of the railroad berm on the eastern side of the development was seen as a positive against storm surge coming up from the coast, but it also served as an impediment for heavy rainfall flowing out of the neighborhood toward the coast. After a city mapping project in 2002, additional stormwater storage areas were added to the basin, a diversion project was built to intercept runoff on the east side of Shawdowmoss, and a culvert was built to move more water from the townhome complex to a nearby pond. Those improvements were designed to handle 20 percent more stormwater.
That didn’t prevent flooding in the neighborhood in 2015 or 2016. The townhomes and several other homes in the subdivision filled with several feet of water in both cases. Those are among the homes Charleston has proposed to buy, with homeowners’ permission, and demolish with federal mitigation funds.
The area around Shadowmoss continues to be developed at a rapid pace, but builders in those neighborhoods now face strict runoff regulations. In most of the state, stormwater systems in new developments must be designed to handle—through outflow or absorption—the runoff of 10-year or 25-year floods. After its 2002 mapping project, Charleston required all new development in the Church Creek basin be designed to handle runoff of a 100-year flood. “We have to look at our options today, make smart choices, and look ahead with the best science in mind,” Cabiness says.
Joshua Robinson is on the leading edge of such a smart-building trend. His firm, Robinson Design Engineers, created a low-impact concept for the Fox Hollow subdivision on James Island, near Charleston. “With low-impact design, you try to mimic the natural hydrology,” Robinson says. “You slow down the movement of water with vegetation so it can infiltrate.”
The 2.65-acre Fox Hollow development features nine homes built with raised crawl spaces on a slight berm on one side of a narrow, winding road, with a stormwater detention swale on the other side. There are no pipes to direct rainfall. Water rose out of the swale and into the road, but the homes didn’t flood in October 2015 or during Hurricane Matthew.
Building better flood maps
Accurate flood mapping is another important component of resilience, and the science behind it keeps getting better. In August 2016, the National Oceanic and Atmospheric Administration (NOAA) launched the National Water Model, a new forecasting tool designed to offer more detailed and timely flood forecasts. Powerful NOAA computers crunch data from more than 8,000 U.S. Geological Survey (USGS) gauges nationally, creating simulations for 2.7 million locations.
“This model expands our forecast locations 700 times and generates several additional water variables, such as soil moisture, runoff, stream velocity, and other parameters to produce a more comprehensive picture of water behavior across the country,” says Thomas Graziano, director of NOAA’s Office of Water Prediction.
The model might have helped emergency personnel during the October 2015 floods. After Hurricane Matthew, it factored in rainfall and soil conditions in the Black River watershed around Kingstree and -correctly forecast the river would peak at about half the volume of the 2015 flood.
In South Carolina, College of Charleston professor Norman Levine is creating a mapping tool to forecast flooding at a more precise level. Funded by a NOAA grant obtained through the S.C. Sea Grant Consortium and the Charleston Resilience Network, Levine’s mapping tool uses LiDAR laser-measured elevations accurate to within +/– 5 centimeters (about 2 inches) to show which portions of Charleston County will flood during certain conditions. The maps factor in rainfall amounts, tidal stages, and stormwater infrastructure, including locations of storm drains and size of pipes. Eventually, they will incorporate soil type, number of trees, locations of wetlands, and percent of impervious surface, Levine says.
A prototype of the mapping tool proved incredibly accurate during an October 2015 test run. It estimated extreme flooding that coincided with a tidal event, called a “King Tide,” would reach the edge of a fountain at the intersection of Morris and Jasper streets in Charleston. It also predicted the street would flood but not the alley between houses across from the fountain. Photos taken during the King Tide almost identically match the mapping tool’s blocky one-meter estimates.
The team working with Levine is updating those maps and expanding them to include the entire county under the NOAA grant. Then Elizabeth Fly, coastal climate extension specialist with the Consortium, will lead an effort to help community leaders, infrastructure managers, and the general public understand how the maps can be utilized.
The maps can be tools to guide emergency officials on where to place barriers to stop drivers from entering high water, and where to position rescue boats before a flood. They could inform the renovation of buildings and improvements to infrastructure on the nearly built-out Charleston peninsula. The maps can also help position neighborhoods to be better prepared for what may come next.
Hurricane Floyd taught lessons in 1999
The most recent severe widespread flooding in South Carolina that occurred before October 2015 was during Hurricane Floyd, which hit Horry County harder than any other. Floyd damaged more than 1,000 homes in Horry County, and $8.6 million in federal and state mitigation funds allowed the county and the city of Conway to buy out about 100 properties for demolition, according to FEMA.
Randy Webster, Horry County’s emergency management director, hopes others in the state will learn from the Floyd fallout in his county. Buyouts work best if the homes purchased can be clustered together. In two communities on the banks of the Waccamaw River, only a few homeowners took the post-Floyd buyout. Many homes in those neighborhoods flooded in October 2015 and again after Hurricane Matthew in 2016.
“We have a lot of little donut-hole FEMA properties,” Webster says. “We don’t have enough all together to create a wetland to help with flooding. We learned from that, and from this point forward, we will target areas to create wetlands.”
During the 2015 and 2016 events, Horry County emergency officials at least knew what areas were likely to flood as rivers began to swell with rain and runoff. They had the Floyd experience as well as accurate readings from upstream river gauges. George-town and Williamsburg counties didn’t have recent flooding experience or as much river data available. USGS, which manages river-level monitoring systems nationwide, has no gauges in Georgetown County, and few in Williamsburg.
“We had to make river-level forecasts using old-school methods,” says Sam Hodge, George-town County’s emergency management director. “We used sign posts, even broken down tractors in yards. You see how high the water is on the tires in the morning, then check later in the day. You could see the wave as it moved across the county, but it took us a while to figure out the rise and fall.”
Upstream of Georgetown County during the 2015 flood, a gauge established in 1973 on the Black River in Kingstree hit 22.65 feet, nearly three feet higher than the highest previous flood. Georgetown County residents knew the water was coming, they just didn’t have a good handle on when and where to evacuate or when they could safely return to their homes.
Hodge praised USGS, which rushed out 16 teams to measure high-water marks and place rapid-deployment gauges in local rivers in October 2015. John Shelton, supervisory hydrologist with the USGS in South Carolina, acknowledged the 2015 flood brought to light several gaps in the system. His agency would like to have more gauges, but it relies on state or local agencies and private businesses to pick up the cost of installing and maintaining them.
High-tech gauges, which beam information to satellites, cost $15,000-$18,000 up-front and about $15,000 per year to operate. There are 164 gauges in the state providing real-time data. The number has increased steadily in recent years, but gauge density is lacking in South Carolina compared to neighboring states, Shelton says. Legislation introduced during the 2016 session to appropriate state funds for 70-100 new gauges failed to gain approval.
The USGS and coastal emergency officials made the most of their lessons from 2015. As forecasts indicated Hurricane Matthew was going to bring heavy rain to coastal South Carolina, local officials knew to ask for rapid-deployment gauges before the storm’s arrival. And as Matthew’s impacts transitioned from coastal hurricane surge to inland flooding, some of the gauges were moved to inland communities, Shelton says. The state had fewer gauges available—nine in 2016 versus 13 in 2015—because it couldn’t borrow gauges from storm-threatened Georgia this time. But earlier and more strategic deployment allowed those fewer gauges to provide more timely data to emergency officials.
NOAA’s new National Water Model offers another alternative for places like northwestern Georgetown County with few permanent USGS gauges. In addition, a new tool in South Carolina could help by making it easy to find water quantity and water quality data generated by USGS, U.S. Forest Service, S.C. Department of Natural Resources, S.C. Department of Health and Environmental Control, and university researchers. Prompted by difficulty locating that data during the October 2015 flood, the S.C. Sea Grant Consortium pulled together those entities to create the S.C. Coastal Water Monitoring Network and design an online portal to make the sharing of their information easier.
Lessons can be upbeat
While most of the lessons learned from the October 2015 flooding were practical, one was especially heartening: People really want to help. Volunteer groups flocked to hard-hit communities. The challenge was how to take advantage of their offers. “We know our local volunteer agencies, but when volunteers were coming from everywhere, it was kind of overwhelming,” says Hodge, Georgetown County’s emergency management director.
Georgetown and Williamsburg county officials found residents were more comfortable dealing with local groups, so they channeled monetary donations through the local United Way, says Stanley Pasley, county supervisor in Williamsburg County. The United Way ended up hiring a temporary coordinator to handle the volunteers and donations.
A year after the 2015 flooding, nearly 1,200 volunteers from the charity Eight Days of Hope flocked to the Kingstree-Andrews area for a blitz recovery effort to repair homes. Three weeks before the October blitz, volunteers Johnny Wildes and Garrett Ganas of Waycross, Georgia, were on the advance team assessing what work needed to be done. They found homes with gaping holes in the roofs, walls speckled with mold, or entire walls torn out to remove mold.
Compared to those families, Martha McFadden was lucky. The 2015 floodwater from a nearby creek reached the edge of the crawl space on the back of her modest home in rural Williamsburg County, but she didn’t have to evacuate. A year later, she had a few moldy spots on the ceiling and on a bathroom wall, a collapsed roof over the garage, and a weathered tarp on the roof over a bedroom. “I sit in my chair when it rains and pray the water doesn’t come through,” McFadden says. “I get scared every time I hear about a storm.”
Wildes and Ganas checked out the damage to McFadden’s house and included it on the Eight Days of Hope project list. McFadden thanked them for their willingness to help, and, after a closing prayer, there were hugs all around.
Unfortunately, the volunteers ended up spending the first few days clearing 140 trees Hurricane Matthew had tossed onto buildings and roads. They still managed to repair 70 homes. Fortunately, the Black River in Kingstree and Andrews didn’t rise as high after Hurricane Matthew. But the 2016 floods brought the same type of destruction to communities 50-60 miles away on the Little Pee Dee and Lumber rivers.
“The biggest takeaway for me and for the county is no one could have imagined the extreme devastation that took place in such a short period of time,” Pasley says of the 2015 flooding. “A lot of our folks who experienced the storm in the most dire manner, they’re experiencing a new way of life, a new norm. It changed life permanently.”
Can momentum be maintained?
But will the October 2015 floods and Hurricane Matthew’s destructive visit in 2016 really change the way we live?
Will people clean debris from their ditches the next time the forecast calls for 10 inches of rain? Will they treat heavy rainfall predictions like hurricane forecasts and evacuate low-lying property? Will drivers heed the “turn around, don’t drown” warnings?
Will homeowners outside of flood zones buy flood insurance to protect their investment? Will communities give flood potential more consideration as they update building codes and zoning plans? Will builders design new homes and new developments to better handle floods?
Specific steps like those are important, but the Consortium’s Fly thinks truly building resilience depends in part on changing attitudes.
“Disasters such as these are emotional events for people, and often cause those affected to want to build back to the way things were,” Fly says. “What’s important post-event is to act on the emotion and the motivation people have to not only build back, but build back smarter so that maybe next time we can reduce the damage and the suffering.”
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