The catastrophic flash flood that struck the Hill Country of Texas in the early hours of July 4 has claimed at least 138 lives. Among the deceased are 27 individuals linked to Camp Mystic, a long-established Christian summer camp situated along the Guadalupe River. The tragedy escalated further with the news of two additional missing persons from the camp, alongside Fire Chief Michael Phillips of Travis County, who was swept away while attempting a rescue on July 5.
This calamity marks a probable death toll ranging from 138 to 141, making it the 10th deadliest flash flood in U.S. history and the most devastating since 1976, when 144 lives were lost in the Big Thompson River flood in Colorado.
In light of this disaster, it is crucial to examine the deadliest floods in U.S. history. We categorize these events into flash floods, river floods, and storm surge floods. These categorization efforts help put such tragic events into historical context, evaluating whether contemporary disaster preparedness and weather forecasting practices are effectively mitigating fatalities, especially given the challenges posed by climate change and the increasing number of people residing in flood-prone areas. The recent considerable loss of life — the highest seen from flash flooding in nearly five decades — underlines the urgent need for enhanced protective measures against such disasters.
Flash floods are particularly perilous due to their rapid onset, resulting from intense rainfall over very short durations, often exacerbated by compromised dams or levees. Their swift nature contributes significantly to their danger; as noted in a 2021 study, they constitute the deadliest type of flooding, accounting for over 86% of related fatalities that often occur when individuals attempt to navigate floodwaters. The directive remains clear: “Turn around, don’t drown!”
Conversely, river floods develop more gradually, spanning hours to days, as rivers swell from prolonged rains or snowmelt. The main hazards here arise from both the depth and duration of flooding rather than its speed.
Storm surge floods arise when hurricane-generated winds force surge water ashore at landfall, resulting in particularly destructive and hazardous conditions due to debris swept along with the surge.
Determining accurate death tolls from flooding events presents considerable challenges, especially as some severe storms lead to both flash and river flooding. Notably, Hurricane Agnes in 1972 and Hurricane Diane in 1955 generated significant fatalities predominately from freshwater flooding; however, they are not categorized solely under flash floods. Complications relating to historical data often mean that death counts can vary significantly depending upon sources consulted, with underestimates being far more prevalent than overestimates. Dr. Wayne Blanchard, a retired FEMA disaster expert, maintains a meticulously researched database of fatalities associated with major American weather events. This report utilizes information from Blanchard’s site along with insights from Christopher C. Burt, a weather historian, to compile a list of the deadliest flash floods in history, omitting deaths linked to structural failures like the St. Francis Dam incident in 1928, which resulted from flaws rather than storms.
The following are details of the top 15 most lethal flash floods recorded:
1. Johnstown Flood (Great Flood of 1889): 2,209-3,188 deaths
The most devastating flash flood in American history transpired on May 31, 1889. Heavy rainfall triggered the catastrophic failure of the South Fork Dam on the Little Conemaugh River, approximately 14 miles from Johnstown, Pennsylvania. The aftermath claimed 2,209 lives, with an additional 979 unaccounted for and presumed dead.
2. Heppner, Oregon flood, June 14, 1903: 247-251 deaths
A vicious flash flood struck Heppner after intense rains ravaged the Willow Creek watershed, creating a wall of water measuring 40 feet high. The destruction was overwhelming; only three businesses and one-third of the town’s homes remained standing in its wake. It wasn’t until the 1990s that Heppner’s population reached its pre-flood level of 1,400 once more.
3. Black Hills, South Dakota flood and dam break, June 9-10, 1972: 236-238 deaths
Following heavy thunderstorms, the Black Hills region of South Dakota experienced destructive flash flooding. Rapid City was particularly impacted when debris-clogged Canyon Lake Dam failed, resulting in a deluge that led to a significant loss of life and property.
4. Central Texas tropical depression, September 8-10, 1921: more than 224 deaths
This flooding incident is challenging to categorize strictly as flash flooding; however, it fits as fatalities occurred along riverbanks that experienced rapid inundation. Covering about 10,000 square miles, this broad event saw a high concentration of deaths among individuals from Mexico residing in the San Antonio river valleys.
5. Republican River flood, May 31-June 1, 1935: 159-168 deaths
Heavy rains falling across eastern Colorado and southwestern Nebraska led to the Republican River’s flooding. The swift rise of the river was primarily responsible for the majority of fatalities, qualifying this incident as a relevant example of a weather-driven flash flood.
6. Virginia flash floods from Hurricane Camille, August 19-20, 1969: 153 deaths
Hurricane Camille, which initially made landfall in Mississippi as a Category 5 storm, weakened to a tropical depression over Virginia, bringing extensive torrential rains exceeding eight inches and resulting in a significant flash flood that ranked sixth in U.S. history for fatalities.
7. Lehigh River Valley, Pennsylvania, flood, June 4-5, 1862: about 150 deaths
A rainstorm that lasted 24 hours in June 1862 led to a flash flood in the Lehigh River Valley, resulting in the death of approximately 150 people. Comprehensive accounts can be found in Ben Gelber’s “The Pennsylvania Weather Book,” a vital reference for Pennsylvania’s weather history.
8. Pueblo, Colorado flood, June 3-5, 1921: more than 148 deaths
The Arkansas River overran its levees following torrential downpours, leading to devastation in Pueblo, Colorado, where more than 500 homes and nearly 100 businesses were destroyed as a result.
9. Big Thompson River, Colorado flood, July 31, 1976: 144 deaths
On this day, a stalled thunderstorm dumped 12-14 inches of rain near Estes Park, Colorado, leading to severe flooding; notably, an estimated 2,500-3,500 individuals were present in Big Thompson Canyon during the state’s centennial celebrations at the time.
10. Central Texas floods, July 4-5, 2025: 138-141 deaths
The remnants of Tropical Storm Barry, which initially made landfall in northeastern Mexico on June 29, resulted in devastating rains, causing floods across Central Texas.
11. Williamsburg, Massachusetts, flood and dam collapse, May 16, 1874: 138-139 deaths
Rapid rains filled the nearly brimming Williamsburg Reservoir, which ultimately failed and obliterated four towns in western Massachusetts in less than an hour. George Cheney rode his horse downstream, desperately attempting to raise the alarm before the dam burst catastrophically.
12. Pittsburgh, Pennsylvania, flood, July 26, 1874: 134 deaths
This classic Pennsylvania flash flood affected Allegheny City and Charter Valley, leading to a death toll of 134 in and around these towns, while Pittsburgh itself experienced relatively minor damage without reported fatalities.
13. Oil Creek, Pennsylvania flood/dam failure, June 5, 1892: 126-139 deaths
Torrential rains caused the failure of an earthen dam near Titusville in northwestern Pennsylvania, sending a flood sweeping through the town where oil ignited atop the rising waters, compounding the disaster.
14. Buffalo Creek, West Virginia, flood, February 26, 1972: 126 deaths
A dam failure at a coal slurry impoundment site lead to inundation from a wall of wastewater, resulting in subsequent flooding across 16 coal towns situated along Buffalo Creek Hollow after torrential rains.
15. Pennsylvania St. Patrick’s Day flood, March 17-20, 1936: 107 deaths
While this flood event did not feature particularly extreme rainfall, the runoff following a deep snowpack and ice-frozen ground resulted in one of the highest flood stages on record for Pittsburgh. Discrepancies surround the reported death toll, making it challenging to ascertain the exact numbers.
Beyond flash floods, the U.S. has also weathered considerable fatalities due to river floods, forming another significant category of deadly flooding events. The categories of flood types show how flood-related deaths and their consequences have evolved over time, with a notable absence of recent deaths among the top river flood incidents.
Death tolls for such events can be correspondingly unreliable based on the historical context. Cary Mock, a climatologist affiliated with the University of South Carolina, indicated that some fatalities in California during floods from 1861-1862 might have stemmed from extreme cold rather than flood conditions. He also suggested existing estimates for several notable historical flooding events may understate the actual number of deaths.
A separate category entirely, storm surge floods, has also seen major fatalities over the years, predominantly aggravated by hurricanes. The nature of hurricanes makes it difficult to isolate storm surge deaths, as fatalities often derive from several causes, including storm surge, wind-related incidents, freshwater floods, sunk vessels, and tornadoes. Nevertheless, an attempt was made to categorize storm surge fatalities separately in the context of significant hurricanes. The ten deadliest storm surge-related flood events in U.S. history include:
1. Great Galveston Hurricane, Texas, September 9, 1900, 7,200-12,000 deaths
Regarded as the deadliest weather event in U.S. history, the catastrophic storm surge, alongside numerous fatalities inflicted by wind, accounted for the vast majority of the destruction.
2. San Ciriaco Hurricane, Puerto Rico, August 8, 1899, about 3,400 deaths
This death toll pertains specifically to Puerto Rico, with the majority resulting from the storm surge. Additional deaths occurred at sea but are not included in this accounting.
3. Great Okeechobee Hurricane, Florida, September 16, 1928, 2,500-3,500 deaths
The majority of fatalities stemmed from storm surge that overwhelmed protective dikes and led to flooding in farming communities surrounding Lake Okeechobee.
4. Sea Islands Hurricane, Georgia and South Carolina, August 27-28, 1893, 1,000-2,500 deaths
The surge produced by this Category 3 hurricane was responsible for nearly all of the fatalities reported.
5. Hurricane Cheniere Caminanda, Louisiana, Mississippi, Alabama, October 1-2, 1893, 1,700-2,000 deaths
Again, the overwhelming majority of deaths stemmed from storm surge.
6. 1919 Hurricane, Texas, September 14, 1919, 600-1,000 deaths
With a storm surge of up to 16 feet impacting Corpus Christi, the hurricane led to significant casualties, which do not include numerous deaths from ships that sank at sea.
7. 1818 Hurricane, Galveston, Texas, September 12-13, about 1,000 deaths
This toll is derived from storm surge and incidents linked to ships anchored near the coastline amid the tempest.
8. Hurricane Katrina, Louisiana, Mississippi, Alabama, August 29-30, 2005, 513-820 deaths
The National Hurricane Center’s updated assessment categorizes 520-827 deaths as direct from the hurricane, leading to a later total assessment of 1,392 lives impacted.
9. 1881 Hurricane, South Carolina and Georgia, August 27, 1881, about 700 deaths
Majority of deaths attributed to storm surge resulting from this hurricane, rated officially as a Category 2, though experts propose it may have been a Category 3.
10. Hurricane Audrey, Louisiana, June 27, 1957, about 526 deaths
Lasting impacts from this hurricane predominantly arose due to the surge, although the overall count includes various related deaths.
In conclusion, the ramifications of flooding in all its forms underline a critical need for ongoing evaluations of disaster preparedness and responsiveness measures to mitigate future tragedies. As highlighted by the high toll from the recent flash flood, communities must adapt and prepare to ensure they are equipped for the inevitable challenges posed by extreme weather events related to climate change.
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