1972 Black Hills flood

1972 severe flooding in the Rapid City metropolitan area, South Dakota, USA Canyon Lake Dam the dam in Texas Canyon Dam (Texas) May 2025 June 2019 Black Hills flood of 1972 June 9–10, 1972 $165 million (1972 USD) 238 Rapid City, South Dakota area The Black Hills Flood of 1972, also known as the Rapid City Flood, was the most detrimental flood in South Dakota history, and one of the deadliest floods in U.S. history. The flood took place on June 9–10, 1972Schwarz Francis K. Hughes Lawrence A. Hansen E. Marshall Petersen M.S. Kelly Donovan B. The Black Hills-Rapid City Flood Of June 9-10, 1972: A Description of the Storm and Flood Geological Survey Professional Paper 1975 877 https://pubs.usgs.gov/pp/0877/report.pdf 9 September 2026 in the Black Hills of Western South Dakota. Rapid Creek and other waterways flooded due to 15 in mm of rain in a small area over the eastern Black Hills. Severe flooding through the Black Hills resulted in 238 deaths The 1972 Black Hills-Rapid City Flood Revisited United States Geological Survey October 15, 2007 https://sd.water.usgs.gov/projects/1972flood/ https://web.archive.org/web/20071009114711/http://sd.water.usgs.gov/projects/1972flood/ October 9, 2007 dead mdy-all and total damages of $165 million USD ($US 160000000 1972 in US dollarsUS). The majority of the loss of life and damage occurred in Rapid City, where business and houses had been constructed in the Rapid Creek floodplain. In the aftermath of the flood, new zoning codes and floodway designations resulted in a redevelopment of the floodplain as mainly parks and recreation spaces to prevent future loss of life.NOAA The Black Hills Flood of 1972 https://www.weather.gov/unr/1972-06-09 National Oceanic and Atmospheric Administration National Oceanic and Atmospheric Administration 9 September 2026 Background In 1972, Rapid City had a population of approximately 43,000 people.Strahl Joseph A. Lieb Herbert Longsdorf Lawrence Natural Disaster Survey Report 72-1: Black Hills Flood of June 9, 1972 1972 US Department of Commerce Washington, DC https://babel.hathitrust.org/cgi/pt?id=uiug.30112104059289&view=1up&seq=1 9 September 2026 Rapid Creek flows through the center of the city, and by the 1970s much of the floodplain had been developed for housing and business. As the city grew through the 1900s, dams on Rapid Creek were built for irrigation, drinking water supply, and recreation, including Canyon Lake Dam in 1938 and Pactola Dam in 1956.USACE Historical Vignette: The Rapid City Flood, June 1972 https://www.nwo.usace.army.mil/Media/Fact-Sheets/Fact-Sheet-Article-View/Article/581806/historical-vignette-the-rapid-city-flood-june-1972/ United States Army Corp of Engineers: Omaha District United States Army Corp of Engineers 9 September 2026ASDSO Case Study: Canyon Lake Dam (South Dakota, 1972) https://damfailures.org/case-study/canyon-lake-dam-south-dakota-1972 Dam Failures Association of State Dam Safety Officials 9 September 2026 Precipitation event In the week leading up to the flood, smaller rain events were recorded at Pactola Dam, including 2.49 inches on June 5th. By June 9th, the soils were likely still saturated, which would have increased the amount of runoff. On June 9th, the orographic lifting ability of the Hills enabled an easterly bringing moist air to rise and contribute water to a long series of convective cell thunderstorms, which dropped heavy showers on the eastern Black Hills.Nair, Hjelmfelt, and Pielke 1756 The maximum recorded rainfall for the storm, taken at Nemo, SD, was 15 inches in just over six hours. This was estimated at 90% of the probable maximum precipitation (PMP), which is the maximum amount of precipitation possible in an area given perfect meteorological factors. Due to unusually light winds at higher elevations, the storms remained almost stationary over the eastern slopes of the Black Hills from about 6 pm on June 9th to 2 am on June 10th. A mesoscale cloud mass moving in from northeastern Colorado contributed moisture and increased the vertical motion of the system, likely amplifying the impacts of the storm.Thompson 164 Cloud seeding experiments being conducted by the Institute of Atmospheric Sciences on clouds west of Rapid City were speculated to have contributed to the unusual amount of rain. However, there is no evidence that the two phenomena were related.Arnett Dennis Flooding The intense rain, combined with the already saturated soils in the upper watershed, resulted in a huge amount of runoff. As rain continued throughout the evening of June 9th, flash flood warnings were radioed throughout the eastern Black Hills, with the Rapid City mayor issuing an evacuation order for low-lying areas at 10:30 pm. Canyon Lake Dam, an earth-fill dam constructed in 1938, was located 7 miles upstream of Rapid City on Rapid Creek. During the flood, the dam accumulated severe debris on the emergency spillway as the rainfall continued. Despite attempts to clear the obstructions, the spillway remained inoperable, and water overtopped the dam crest. The dam failed at 10:45 pm on July 9th. However, the dam failure did not significantly contribute to the flood peak, likely because the dam did not give way suddenly. Of the 371 sq. mi. of the Rapid Creek watershed, only about 51 sq. mi. downstream of Pactola Dam contributed to the flooding at Rapid City, due less rainfall in the upper watershed and the flood control impacts of the dam. The peak flow in Rapid Creek at Rapid City was estimate at 50,000 cubic feet per second.Larimer Owen J. HA-511: Flood Of June 9-10, 1972, At Rapid City, South Dakota https://pubs.usgs.gov/ha/511/plate-1.pdf USGS United States Geological Survey 9 September 2026 However, due to the short duration of flow (Rapid Creek was no longer inundating the floodplain by 5 am on June 10th), the volume of flow only about 13,000 acre-ft over the two-day period. Flooding was also observed on other local streams, including Boxelder Creek, Battle Creek, Elk Creek, and Bear Butte Creek. Victims and damage thumb|300px|Cars jumbled together by the flood Throughout the region, the flood caused a large amount of damage, but the most severe of the impacts were in Rapid City, where 230 of the 238 casualties occurred. The other eight victims were from Keystone, South Dakota, when severe flooding from Battle Creek inundated the town. Among the victims were Eldon L. Smith, a South Dakota state senator,https://sdlegislature.gov/Historical/Legislator/Profile/942 Eldon L. Smith South Dakota Legislature March 24, 2024 and a disproportionate number of Native Americans living in Rapid City.https://academic.oup.com/whq/article-abstract/52/3/305/6297544?redirectedFrom=fulltext 10.1093/whq/whab076 Erasing Indian Country: Urban Native Space and the 1972 Rapid City Flood 2021 Hausmann Stephen R. Western Historical Quarterly 52 3 305–329 subscription In addition to the lives lost, the flood caused widespread economic damage. Flood waters displaced large rocks, trees, trailers, and vehicles, and carried homes away.Thompson 166 A total of 1,335 homes were destroyed or rendered uninhabitable, and 2,820 homes were damaged, with 200 businesses damaged and over 5,000 cars destroyed. The total cost of the 1972 Black Hills flood totaled $165 million, including infrastructure and utilities. Aftermath Though evacuation orders and flash-flood warnings were determined to have saved many lives, the National Weather Service office at Rapid City lacked communication equipment to receive urgent radar updates and severe weather alerts at the time of the flood. Since the flood, additional real-time monitoring stations have been installed on local streams in order to better inform forecasters and residents about stream rise. Before the flood, Rapid City had already begun to implement floodplain management policies. In the aftermath, additional programs were developed to prevent future loss of life. A floodway was designated through the center of the floodplain, a levee was constructed to protect local businesses, and the floodplain was rezoned to prevent the construction of houses and motels. The majority of the flood plain was redeveloped as green-space.Ray Charles Micheal 40 years after Killer Flood, A reshaped City Reflect https://www.npr.org/2012/06/08/154576917/disastrous-s-d-flood-caused-national-wake-up-call NPR National Public Radio 9 September 2026 Canyon Lake Dam was reconstructed to allow passage of a flood of the size of the 1972 event. Notes 33em Further reading Dennis, Arnett. A Memoir of the Rapid City Flood of 1972. 2010. Print. Rapid City Journal. Turning Point: Remembering the Rapid City Flood of 1972. 2022. Pediment Publishing. External links NPR interviews survivors on the 50th anniversary of the flood. The Rapid City Public Library offers an online digital archive which collects audio and video recordings of survivors, written accounts and photos from survivors, as well as news broadcasts from the 1972 flood. An interactive GIS map of the flood to commemorate the 50th anniversary. 44 03 28 N 103 17 13 W region:US-SD_type:landmark_source:kolossus-dewiki title Category:1970s floods in the United States Category:1972 natural disasters in the United States Category:1972 in South Dakota Category:Black Hills Category:Dam failures in the United States Category:Natural disasters in South Dakota