The heartbreaking toll from the flash flood that swept through the Hill Country of Texas early morning on July 4 has reached 138, including 27 from Camp Mystic, a Christian summer camp for schoolgirls with nearly a century of operations along and near the Guadalupe River. Two additional people from Camp Mystic remain missing, in addition to Fire Chief Michael Phillips of Travis County, who was swept away during a rescue attempt on July 5. This makes the probable death toll 138-141 — the 10th-highest on record for a U.S. flash flood, and the largest since 1976, when 144 perished in Colorado’s Big Thompson River on July 31, 1976.
Here, we present the deadliest U.S. floods on record, divided into three categories: flash floods, river floods, and storm surge floods. Such lists help us place deadly disasters in historical context to see if modern disaster preparedness and weather forecasts are keeping death tolls from reaching historic levels — despite climate change and increasing vulnerability, such as more people living in flood plains. The fact that we just saw the highest toll from a flash flood in 49 years should be a warning sign that we need to do more to safeguard people from flash flooding.
Flash floods: the most deadly type of flood
Flash floods are a sudden, rapid rise in water caused by intense rainfall over a short period — minutes to a few hours — often in localized areas, sometimes exacerbated by a dam or levee failure. Their speed makes them very dangerous, and they are the deadliest type of flood, according to a 2021 study, An Analysis of Flood Fatalities in the United States, 1959-2019. According to that research, over 86% of all flood deaths are from people who purposely drive or walk into floodwaters. Turn around, don’t drown!
River floods develop more slowly over hours to days, as rivers rise from extended or repeated rainfall or snowmelt. They occur along large rivers or flood plains, and their chief danger comes from the depth and duration of flooding, not their speed.
Storm surge floods occur when the strong winds of a hurricane push a mound of water ashore at the time of landfall. The battering-ram effect from debris riding on top of the storm surge brings an extra element of danger.
Lots of uncertainty in death tolls
Creating a list of the deadliest flash floods is complicated because some extreme storms cause sudden flash flooding in addition to slower river flooding. This was the case for two flood events left off this list – Hurricane Agnes of 1972, whose freshwater flooding killed 114 people in the Northeast U.S., and Hurricane Diane, whose floods killed 221 people in August 1955 in the Northeast one week after torrential rains from Hurricane Connie had saturated the soils.
Death tolls from flood events often have considerable variation depending upon the source consulted, especially for older events. Underestimates tend to occur more often than overestimates. The Deadliest American Disasters and Large Loss-of-Life Events website, run by retired FEMA disaster expert Dr. Wayne Blanchard, co-author of the peer-reviewed Bulletin of the American Meteorological Society article “Fatalities in the United States Indirectly Associated with Atlantic Tropical Cyclones,” has a painstakingly researched list of the various sources of death tolls for most major American weather disasters. The list in Fig. 1 is based on the most commonly cited death tolls from official government sources, leaning on advice from Blanchard’s website plus research from weather historian Christopher C. Burt (author of the classic reference book “Extreme Weather: A Guide and Record Book”) for the final choice.
The list does not include the 600 deaths from the 1928 failure of the St. Francis Dam near Los Angeles, which arose from structural flaws, not a storm.
Below are details for each of the top 15 most deadly flash floods.
1. Johnstown Flood (Great Flood of 1889): 2,209-3,188 deaths
The unquestioned deadliest flash flood in American history occurred May 31, 1889, when heavy rains led to the catastrophic failure of the South Fork Dam on the Little Conemaugh River, about 14 miles (23 km) upstream from Johnstown, Pennsylvania. The flood killed 2,209, with 979 missing and presumed dead.
2. Heppner, Oregon flood, June 14, 1903: 247-251 deaths
Torrential rains over the Willow Creek watershed triggered a violent flash flood that sent a wall of water 40 feet high through Heppner, wrecking all but three of the town’s businesses and two-thirds of its homes. It was not until the 1990s that Heppner’s population rebounded to its pre-flood levels of 1,400.
3. Black Hills, South Dakota flood and dam break, June 9-10, 1972: 236-238 deaths
Heavy thunderstorms caused devastating flash flooding throughout the Black Hills of South Dakota. Most of the damage and fatalities occurred in Rapid City, which flooded when the Canyon Lake Dam became clogged with debris and failed.
4. Central Texas tropical depression, September 8-10, 1921: more than 224 deaths
This flood is tricky to categorize because it could arguably be called a regional flood or several flash floods affecting several different rivers. It is included here since it seems the fatalities were along river banks that experienced flash flooding. The area of coverage was huge — about 10,000 square miles. A USGS report of the event is very detailed on the deaths reported. Many fatalities occurred among people from Mexico living along river valleys in the San Antonio area.
5. Republican River flood, May 31-June 1, 1935: 159-168 deaths
Heavy rains in eastern Colorado and southwestern Nebraska flooded the Republican River. It was the speed of the river’s rise that led to most of the deaths — the definition of a weather-related flash flood.
6. Virginia flash floods from Hurricane Camille, August 19-20, 1969: 153 deaths
After its devastating landfall in Mississippi as a Category 5 storm, Hurricane Camille weakened to a tropical depression over Virginia, bringing widespread torrential rains in excess of eight inches that triggered the sixth-deadliest flash flood in U.S. history.
7. Lehigh River Valley, Pennsylvania, flood, June 4-5, 1862: about 150 deaths
This was a flash flood triggered by a rainstorm that occurred over 24 hours on June 4 and 5. Full details can be found on pages 177-178 in Ben Gelber’s “The Pennsylvania Weather Book,” the most authoritative publication concerning Pennsylvania weather history. There are quite a few photos of the devastation created by this event.
8. Pueblo, Colorado flood, June 3-5, 1921: more than 148 deaths
Heavy rains sent the Arkansas River over its levees, inundating Pueblo, Colorado, destroying more than 500 homes and 98 businesses.
9. Big Thompson River, Colorado flood, July 31, 1976: 144 deaths
A stalled thunderstorm complex dumped 12-14 inches (300–360 mm) of rain near Estes Park, Colorado, including 7.5 inches (190 mm) of rain in one hour. About 600 people lived in Big Thompson Canyon, and 2,500-3,500 people were there on Saturday, July 31, to celebrate the 100th anniversary of Colorado’s statehood on August 1.
10. Central Texas floods, July 4-5, 2025: 138-141 deaths
The remnants of Tropical Storm Barry, which had made landfall as a tropical depression in northeast Mexico on June 29, fed torrential rains that caused devastating flooding in Central Texas.
11. Williamsburg, Massachusetts, flood and dam collapse, May 16, 1874: 138-139 deaths
Heavy rains rapidly filled the nearly full Williamsburg Reservoir, which collapsed, wiping out four towns in western Massachusetts within one hour. George Cheney frantically jumped on his horse bareback and galloped downstream to warn the people of Williamsburg. As he shouted warnings, the dam burst with a tremendous boom that filled the valley. Farmers miles away said it was louder than any thunder they had ever heard.
12. Pittsburgh, Pennsylvania, flood, July 26, 1874: 134 deaths
This classic Pennsylvania flash flood devastated the towns of Allegheny City and Charter Valley just a few miles north of Pittsburgh, which only suffered modest damage and no reported fatalities. Gelber states the death toll was 134 in and around those two towns. He also notes that local newspapers gave widely varying death tolls, but research by Tom Grazulis (in his epic tornado book, “Significant Tornadoes 1680–1991: A Chronology and Analysis of Events”) says that the toll of 134 was originally attributed to a tornado in Erie, Pennsylvania on July 28, 1875, that never occurred, and the figure actually represented the death toll in the Pittsburgh area flood.
13. Oil Creek, Pennsylvania flood/dam failure, June 5, 1892: 126-139 deaths
Torrential rains over northwestern Pennsylvania caused the failure of an earthen dam about seven miles upstream of Titusville. The resulting flood swept through Titusville, damaging an oil refinery, and the oil on top of the flood caught fire, creating a flame-topped wall of water. From a National Weather Service summary of the horrific event:
The burning creek advanced southward into the next community, Oil City. By 6 a.m., it struck. Alarms were raised all over town, with the creek cresting around 9 or 10 a.m. To make matters even worse, several tankers holding benzene were located along the banks of the creek. The whole upper end of Oil City, on both sides of the Oil Creek, were inundated. The benzene ignited and burned most of the second and third ward with 200-300 buildings.
14. Buffalo Creek, West Virginia, flood, February 26, 1972: 126 deaths
Torrential rains led to the failure of a coal slurry impoundment dam managed by Pittston Coal Company. The dam’s failure overwhelmed two other dams, and the resulting flood unleashed a 30-foot (9.1-meter) high wall of black waste water upon the 5,000 residents of 16 coal towns along Buffalo Creek Hollow.
15. Pennsylvania St. Patrick’s Day flood, March 17-20, 1936: 107 deaths
Rainfall from this event was not extreme (in the two-to-seven-inch range, with a maximum of 6.92 inches in Stroudsburg), but it fell on a deep snowpack and ice-frozen terrain. The runoff was incredible. Pittsburgh’s highest flood stage on record was apparently established on March 18 at 46 feet, 21 feet above flood stage. A USGS report published in 1937 has an opening statement claiming 150-200 lives were lost. I (Chris Burt) can find absolutely no corroboration for such a figure anywhere online aside from that reference, and the report gave no details at all so far as these reported fatalities. No other historical references even come close to such a figure. Gelber’s “The Pennsylvania Weather Book” states that the total loss of life in all of the state was “upwards of 100.” The storm affected a wide area from Washington, D.C., to Connecticut, where 29 flood deaths occurred.
Deadliest river floods
The U.S. has also suffered tremendous loss of life from great river floods. We present a list above of the top 15 deadliest, following the guidance of Wayne Blanchard’s Deadliest American Disasters and Large Loss-of-Life Events. Note that all of these top 15 deadliest U.S. river floods occurred more than 50 years ago. The same is true for all of the top 15 deadliest flash floods discussed above, except for the Big Thompson River (1976) and the Guadalupe River in Texas (2025).
As explained above, death tolls can be highly uncertain. In an email, University of South Carolina climatologist Cary Mock noted that some of those who died in the California floods of 1861-1862 may have actually been killed by extreme cold rather than floods.
On the other hand, Mock wrote, “this like many earlier events is massively underestimated; it could well be over 1,000 deaths in California. There are some 1862 articles in newspapers that describe how many hundreds of Chinese laborers drowned, but it’s hard to know how much sensationalism was introduced.”
Mock added that 400 fatalities is likely an underestimate for the 1844 Mississippi/Missouri River floods and that for the May 1771 flood in Virginia, “the safest estimate would seem to be in the dozens, but it could have been a few hundred or more.”
Deadliest storm surge floods
Among the deadliest floods in U.S. history, hurricane storm surge floods predominate. However, it can be tricky to categorize the death tolls from this type of flooding. Hurricane death tolls are typically given as an aggregate number and result from a combination of storm surge, wind, freshwater flooding, ships that sank at sea, and tornadoes. The list above makes an attempt to separate out storm surge deaths from other types of deaths, leaning on data from this site. Notes on the top 10:
1. Great Galveston Hurricane, Texas, September 9, 1900, 7,200-12,000 deaths: Unquestionably the deadliest weather event in U.S. history. The great majority of deaths from the Category 4 hurricane were from a storm surge that inundated Galveston Island under eight to 12 feet of water, but many wind deaths also occurred from flying debris and collapsed buildings.
2. San Ciriaco Hurricane, Puerto Rico, August 8, 1899, about 3,400 deaths: This death toll is only for Puerto Rico, where the storm surge from the Category 4 hurricane was responsible for the vast majority of the deaths. Many additional deaths occurred from ships that sank at sea and are not included here.
3. Great Okeechobee Hurricane, Florida, September 16, 1928, 2,500-3,500 deaths: The vast majority of deaths resulted from a storm surge on Lake Okeechobee from the Category 4 hurricane that overwhelmed the dikes and flooded nearby farming communities.
4. Sea Islands Hurricane, Georgia and South Carolina, August 27-28, 1893, 1,000-2,500 deaths: The vast majority of the deaths were from a storm surge from the Category 3 hurricane, which hit the coast at high tide.
5. Hurricane Cheniere Caminanda, Louisiana, Mississippi, Alabama, October 1-2, 1893, 1,700-2,000 deaths: The vast majority of the deaths were from the storm surge of the Category 4 hurricane.
6. 1919 Hurricane, Texas, September 14, 1919, 600-1,000 deaths: The Category 3 hurricane brought a storm surge of 16 feet to Corpus Christi. At least 127 deaths occurred from ships sunk at sea and are not included here.
7. 1818 Hurricane, Galveston, Texas, September 12-13, 1818, about 1,000 deaths: The death toll was from a combination of storm surge and ships anchored near the coast.
8. Hurricane Katrina, Louisiana, Mississippi, Alabama, August 29-30, 2005, 513-820 deaths: The National Hurricane Center Katrina report (updated in 2023) lists 520-827 direct deaths for the hurricane, of which seven were definitely not from storm surge. The remainder of the direct deaths were probably caused by storm surge, the center said. Hundreds of others died indirectly in the horrific days after Katrina, leading to the center’s assessment that Katrina caused 1392 fatalities in all.
9. 1881 Hurricane, South Carolina and Georgia, August 27, 1881, about 700 deaths: The hurricane brought a storm surge of 15 feet to the coast of South Carolina near Beaufort; the majority of the deaths appear to be from storm surge. Officially, this was rated a Cat 2 storm, but University of South Carolina climatologist Cary Mock commented in an email that this was “likely a Cat 3, as I found a barometer off Tybee that suggests it was 960 mb (not at the center)”.
10. Hurricane Audrey, Louisiana, June 27, 1957, about 526 deaths: The Category 3 hurricane brought a storm surge of 12-15 feet to the coast of southwestern Louisiana. The death toll listed here is only for Louisiana, where storm surge accounted for the vast majority of deaths.
Other candidates: The Long Island Express Hurricane of September 21, 1938, is blamed for 682-712 deaths, and several hundred of these deaths from the Category 3 are from a storm surge that hit the coasts of Long Island, Connecticut, Rhode Island, and Massachusetts. Also, a 1553 hurricane that may have killed 1,700 people on the lower Texas coast is not included here, since the statistics may not be reliable.
Mock wrote, “Regarding storm surge from hurricanes, I think your list is pretty reliable, and most of those storm fatalities in the top five are surge-related. Some of the hurricanes that likely had at least hundreds of fatalities related to surge include the Louisiana 1812 hurricane (also big effects up the Mississippi inland from New Orleans to Baton Rouge) and the SC 1752 hurricane.”
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Great Job Jeff Masters, Christopher C. Burt and Bob Henson & the Team @ Yale Climate Connections Source link for sharing this story.
