The 1972 Black Hills-Rapid City Flood Revisited


—by Janet M. Carter, Joyce E. Williamson, and Ralph W. Teller 

Introduction 

On June 9-10, 1972, extremely 

heavy rains over the eastern Black 

Hills of South Dakota produced 

record floods on Rapid Creek and 

other streams in the area. Nearly 

15 inches of rain fell in about 6 hours 

near Nemo, and more than 10 inches 

of rain fell over an area of 60 square 

miles (Schwartz and others, 1975). 

According to the Red Cross, the 

resulting floods left 238 people dead 

and 3,057 people injured. In addition 

to the human tragedy, total damage 

was estimated in excess of $160 million (about $664 million in 2002 

dollars), which included 1,335 

homes and 5,000 automobiles that 

were destroyed (Schwartz and others, 

1975) (fig. 1). 

June 2002 marks the 30th anniversary of the largest and most costly 

flood event in Black Hills recorded 

history. For many people that lived 

in or visited the Black Hills area on 

June 9-10, 1972, the memory of the 

flood will always be clear. For others, the details are fading along with 

the impetus for preventing another 

flood disaster in the Black Hills area. 

This fact sheet provides a summary 

of some of the hydrologic conditions 

that led up to the 1972 flood, comparisons of the 1972 flood to other 

floods in the Black Hills area, and a 

description of current flood protection and warning capabilities in the 

area. Also, this fact sheet is a 

reminder that extreme floods have 

occurred in the Black Hills and will 

occur again. Continued collection of 

Photograph by Perry H. Rahn, South Dakota School of Mines and Technology 

Figure 1. The 1972 flood destroyed 5,000 automobiles, including these cars that were parked at 

a dealership on East Boulevard. 

hydrologic data in the Black Hills is 

important for flood monitoring and 

preparing for future floods. 

The Flood 

Scattered showers had occurred 

throughout the Black Hills area on 

several days prior to the heavy rains 

that began on June 9. Near Pactola 

Dam, these earlier showers had left 

the soil saturated, which increased 

the amount of runoff for the flood of 

June 9-10 (Schwartz and others, 

1975). 

Rainfall began in the Black Hills 

area on the afternoon of June 9 when 

a group of almost-stationary thunderstorms formed over the eastern Black 

Hills. The heavy rains that fell until 

about midnight partly were the result 

of a strong low-level easterly airflow 

that forced moist air upslope over the 

Black Hills. This strong and sustained orographic effect caused the 

air to rise, cool, become very unstable, and release its moisture in 

repeating thunderstorms. Light 

winds at higher atmospheric levels 

allowed the storms to remain nearly 

stationary, which resulted in 

extremely heavy rainfall. Precipitation totals for June 9-10 ranged from 

4 inches to more than 12 inches in 

the Rapid Creek watershed between 

Pactola Dam and Rapid City (fig. 2). 

In the Boxelder Creek watershed, 

15 inches of rain during a 6-hour 

period was measured at Nemo. The 

heaviest rainfall averaged about four 

times the 6-hour amounts that are to 

be expected once every 100 years in 

the area (National Oceanic and 

Atmospheric Administration, 1972). 

U.S. Geological Survey USGS Fact Sheet FS-037–02 

U.S. Department of the Interior April 2002 
The resulting runoff produced 

record floods (highest peak flows 

recorded) along Battle, Spring, 

Rapid, and Boxelder Creeks. 

Smaller floods also occurred along 

Elk Creek and Bear Butte Creek. 

Although Pactola Reservoir was 

effective in storing runoff that originated upstream of Pactola Dam, the 

heaviest rainfall occurred downstream of the dam. Most of the flow 

that passed through Rapid City 

via Rapid Creek originated in the 

51-square-mile drainage area 

between Pactola Dam and Canyon 

Lake. Flood waters that reached 

Rapid City between 9:30 and 

10:00 p.m. on June 9 carried large 

amounts of debris that clogged the 

spillway of the Canyon Lake Dam. 

The dam at Canyon Lake failed at 

about 10:45 p.m. However, the 

effect of this dam failure (fig. 3) on 

the subsequent flood wave into urban 

Rapid City has been difficult to 

assess because the amount of water 

coming down Rapid Creek and 

several tributaries (accounting for 

86 percent of the peak flow) far overshadowed the amount of water in the 

small lake (Schwartz and others, 

1975). The peak flow of 50,000 

cubic feet per second (ft

3

/s) was carried through Rapid City via Rapid 

Creek at about midnight on June 9, 

while many people were asleep and 

unaware of the impending flood. 

The stage of Rapid Creek (measured 

above Canyon Lake) rose more than 

13 feet in 5 hours during the flood. 

Extreme flooding also occurred 

along Battle Creek and its tributaries 

because this area received some of 

the most intense rainfall. In Keystone, eight people were killed and 

much of the town was washed away. 

High runoff occurred between Hill 

City and Sheridan Lake, where some 

water was stored for a short time and 

slightly reduced the flood peaks 

downstream. Boxelder Creek also 

experienced extreme flooding, 

although total damage was relatively 

low because of the area’s sparse 

development at that time. Significant flooding occurred in the Elk 

Creek and Bear Butte Creek Basins, 

although these basins were not in the 

area of heaviest rainfall. 

The floods struck quickly and 

forcefully, but they did not last long 

nor did they make much impact farther downstream in the basins. Water 

in Rapid Creek within Rapid City 

was back within its banks by 

5:00 a.m. on June 10. All of the 

streams that experienced flooding 

drain into the Cheyenne River, but 

the peaks were diminished considerably by the time they were discharged into the Cheyenne River. As 
Photograph by Perry H. Rahn, South Dakota School of Mines and Technology 

Figure 3. Photograph of the remains of the Canyon Lake Dam the morning after it failed. 

During the flood, the spillway of the dam clogged with floating debris. When the dam failed 

at about 10:45 p.m. on June 9, 1972, a surge of water was sent into urban Rapid City. 

the peak flows moved into less-steep 

terrain, the flows spread out over a 

wide area, and much of the water 

was stored in the flood plains. 

Comparison to Other Black 

Hills Floods 

Although the 1972 Black HillsRapid City flood was the largest 

flood recorded in the Black Hills 

area, numerous previous floods had 

occurred in the area. The earliest 

recorded flood occurred during 

June 10-11, 1878, with an estimated 

peak flow of 7,500 ft3/s on Rapid 

Creek (U.S. Army Corps of Engineers, 1973) and one life lost (Rapid 

City Journal). On May 17, 1883, a 

flood on Rapid Creek resulting from 

heavy rainfall and rapid snowmelt 

washed out many bridges and caused 

extensive damage in Rapid City; the 

peak flow was estimated to be 

8,400 ft

3

/s (U.S. Army Corps of 

Engineers, 1973). 

Annual maximum peak flows 

recorded since 1900 for two gaging 

stations on Rapid Creek—above 

Canyon Lake and at Rapid City—are 

shown in figure 4. The second largest flood recorded along Rapid Creek 

occurred in May-June 1907 with an 

estimated peak flow of 13,000 ft

3

/s 

(U.S. Army Corps of Engineers, 

1973). During the 1907 flood, 

Canyon Lake Dam was overtopped 

and partly washed away, and many 

bridges, roads, and railroad tracks 

were extensively damaged or 

destroyed. On May 11, 1920, heavy 

rain and melting snow caused flooding with an estimated peak flow of 

about 8,000 ft

3

/s (U.S. Army Corps 

of Engineers, 1973) that led to the 

evacuation of approximately 50 

homes and the destruction of several 

bridges. On May 23, 1952, a peak 

flow of 2,600 ft

3

/s was recorded at 

the gaging station above Canyon 

Lake (table 1). A peak flow of 

3,300 ft

3/s was recorded at the gaging station at Rapid City on July 13, 

1962 (table 1). The 1962 flood damaged 120 mobile homes, 2 hotels, 

and more than 400 residences, with a 

total estimated damage of $800,000 

(U.S. Army Corps of Engineers, 

1973), which is about $4.1 million in 

2002 dollars. 

A peak flow of 31,200 ft

3

/s 

occurred at the gaging station above 

Canyon Lake (fig. 5) during the 1972 

flood and was 12 times the previous 

maximum of 2,600 ft

3

/s recorded in 

1952. The peak flow of 50,000 ft

3

/s 

at the gaging station at Rapid City 

during the 1972 flood was more than 

four times the previous estimated 

maximum of 13,000 ft3

/s during 

May-June 1907. The 1972 peak flow 

at this station was more than 15 times 

the previous recorded maximum 

(3,300 ft

3

/s on July 13, 1962) since 

construction of Pactola Dam in 1956. 

Can the 1972 Flood Happen Again? 

The answer is yes. The 1972 flood on Rapid Creek has an estimated 

recurrence interval of 500 years (Burr and Korkow, 1996), which 

means that a flood of this magnitude will occur an average of once 

every 500 years. Every year there is a 0.2-percent chance (1 in 500) 

of experiencing a similar flood. Because of the short period of record 

for Rapid Creek gaging stations, the recurrence interval of 500 years 

may be revised substantially as additional data are collected. 

“Floods are natural and normal phenomena. They are catastrophic 

simply because man occupies the flood plain, the highway channel of 

a river (Bue, 1967).” 
Photograph by Perry H. Rahn, South Dakota School of Mines and Technology 

Figure 5. Photograph of U.S. Geological Survey streamflow-gaging station Rapid Creek above 

Canyon Lake near Rapid City (06412500) the day after the flood. A peak discharge of 31,200 cubic 

feet per second occurred at this site just before midnight on June 9, 1972. In the background are 

the remains of new houses that people were moving into the night of the flood. 

Following the 1972 flood, most of 

the largest subsequent peak flows for 

Black Hills area streams occurred 

during the middle to late 1990’s 

(table 1), which corresponds with the 

wettest period in the Black Hills area 

since 1931 (Driscoll and others, 

2000). However, none of these subsequent peak flows have come close 

to exceeding the peak flows recorded 

during the 1972 flood. Severe flooding occurred in the Black Hills on 

May 8-10, 1995, generally outside of 

the Rapid City area. Damage to 

roads and bridges was widespread; 

rock and mudslides closed highways 

in Sturgis and in Boulder Canyon 

near Deadwood. Many homes suffered water damage. More recently, 

flooding has occurred on Spring 

Creek on May 30, 1996, and in 

Rapid City on June 2, 1997, but 

damage was very minor. 
-- -- --

Table 1. Comparison of 1972 peak flows with other peak flows for selected current (2002) U.S. Geological Survey streamflow-gaging stations 

[ft

3

/s; cubic feet per second; --, no record] 

Peak flows prior to 

June 1972 

Flood of 

June 9-10, 

1972 

Peak flows after 

June 1972 Site 

number 

(fig. 2) 

Station name	 Station 

number 

Period of Year Streamflow 

record (ft

3/s) 

Streamflow Streamflow 

(ft

3/s) Date (ft3/s) 

1 Battle Creek at Hermosa 06406000 1949-72 1952 2,950 21,400 05-08-95 2,400 

2 Spring Creek near Hermosa 06408500 1949-72 1967 772 13,400 05-30-96 6,910 

3 Rapid Creek above Pactola 06410500 1953-72 1965 2,060 228 06-18-98 1,290 

Reservoir, at Silver City 

4 Rapid Creek below Pactola Dam 06411500	 1928-32 

1946-72 

1952 2,170 378 06-07-96 450 

5 Victoria Creek below Victoria 

Dam, near Rapid City 

06412250 6,860 06-15-99 1

73 

6 Rapid Creek above Canyon 

Lake, near Rapid City 

06412500 1946-72 1952 2,600 31,200 06-02-97 1,050 

7 Rapid Creek at Rapid City 06414000	 1903-06 

1942-72 

1962 3,300 50,000 06-02-97 3,190 

8 Rapid Creek near Farmingdale 06421500 1946-72 1947 2,640 7,320 05-27-96 3,830 

9 Boxelder Creek near Nemo 06422500 1945-47 1946 1,180 30,100 06-15-76 1,460 

1966-72 

10 Elk Creek near Elm Springs 06425500 1949-72 1952 8,540 1,880 05-28-96 7,660 

11 Bear Butte Creek near Galena 06437200 1965-69 1965 4,950 19,000 06-18-98 1

541 

12 Bear Butte Creek near Sturgis 06437500 1945-72 1962 12,700 7,220 05-08-95 2

4,310 

1

Period of record since 1972 is 1998-2001. 2

Period of record since 1972 is 1990-2001. 

Today’s Flood Protection 

and Warning 

In the aftermath of the 1972 flood, 

interim and long-range programs 

were initiated and millions of federal 

dollars were spent in Rapid City and 

the surrounding stricken communities (Rahn, 1984). Rapid City 

approved a flood-plain management 

program, known as the “greenway” 

concept, whereby most of the flood 

plain was converted into large parks. 

Many businesses were allowed to 

remain in the flood plain, but houses 

and motels in the floodway were 

either razed or moved to new locations based on the underlying concept that no one should sleep within 

the flood plain. Canyon Lake Dam 

and many bridges were redesigned 

and rebuilt to prevent debris clogs. 

Rapid City and surrounding communities are susceptible to extreme 

flooding because of their location in 

and around the Black Hills. Most 

floods in the Black Hills area are 

caused by intense rainfall over steep 

watersheds, which allows little time 

for warning residents of flood 

threats. 

In 1997, a flood-warning system 

was implemented by the USGS in 

cooperation with the Rapid CityPennington County Emergency 

Management and National Weather 

Service (NWS) (Teller and others, 

2000). Combination precipitation/ 

streamflow-gaging stations (fig. 6) 

monitor rainfall and subsequent rises 

in stream stage on a continuous basis 

during the flood season (AprilOctober). This real-time information 

is relayed via a satellite network to 

the NWS, where forecasters can send 

warning to the public when streams 

rise to threatening levels. Rapid 

City-Pennington County Emergency 

The USGS measures streamflow in terms of cubic feet per 

second. One cubic foot per 

second is equal to about 

448 gallons per minute, 

27,000 gallons per hour, or 

646,000 gallons per day— 

close to the amount needed to 

fill an Olympic-sized swimming 

pool in 1 day. 
Photograph by Brenda J. Athow 

Figure 6. Photograph of a current flood-warning 

system gaging station. Real-time data from the 

gaging station are relayed via a satellite network 

to the National Weather Service and Rapid CityPennington County Emergency Management. 

Management can then coordinate 

emergency response, public safety 

services, and local governmental 

agencies as needed. Currently 

(2002), the USGS collects data at the 

20 flood-warning sites in the Black 

Hills area, which are located along 

Battle, Spring, Rapid, Victoria, Boxelder, Spearfish, and Bear Butte 

Creeks and their tributaries. 

The USGS currently operates a 

network of about 120 continuousrecord streamflow-gaging stations 

and 35 high-flow partial-record 

gages in South Dakota. Miscellaneous annual streamflow measurements also are made at several 

additional sites throughout the State. 

When flooding occurs, the USGS 

mobilizes personnel to collect 

streamflow data in affected areas. 

Streamflow data improves flood 

forecasting, provides additional data 

for flood-frequency analysis that is 

used by the South Dakota Department of Transportation for bridge 

design, and provides information 

for use by emergency management 

agencies before, during, and after 

flooding. 

References 

Bue, C.D., 1967, Flood information 

for flood-plain planning: U.S. 

Geological Survey Circular 539, 

10 p. 

Burr, M.J., and Korkow, K.L., 1996, 

Peak-flow frequency estimates 

through 1994 for gaged streams in 

South Dakota: U.S. Geological 

Survey Open-File Report 96-202, 

407 p. 

Driscoll, D.G., Hamade, G.R., and 

Kenner, S.J., 2000, Summary of 

precipitation data for the Black 

Hills area of South Dakota, water 

years 1931-98: U.S. Geological 

Survey Open-File Report 00-329, 

151 p. 

National Oceanic and Atmospheric 

Administration, 1972, Black Hills 

Flood of June 9, 1972: Rockville, 

Maryland, U.S. Department of 

Commerce, Natural Disaster 

Survey Report 72-1, 20 p. 

Rahn, P.H., 1984, Flood-plain management program in Rapid City, 

South Dakota: Geological Society 

of America Bulletin, v. 95, p. 838-

843. 

Schwartz, F.K., Hughes, L.A., 

Hansen, E.M., Petersen, M.S., and 

Kelly, D.B., 1975, The Black 

Hills-Rapid City Flood of June 9-

10, 1972—A description of the 

storm and flood: U.S. Geological 

Survey Professional Paper 877, 

47 p. 

Teller, R.W., Huse, T.L., and Owens, 

Park, 2000, Development and 

operation of a cooperative floodwarning system, in Strobel, M.L., 

and others, eds., Hydrology of the 

Black Hills—Proceedings of the 

1999 Conference on the Hydrology of the Black Hills: Rapid 

City, South Dakota School of 

Mines and Technology Bulletin 

no. 20, p. 59-62. 

U.S. Army Corps of Engineers, 

1973, Flood Plain Information— 

Rapid Creek, Rapid City, South 

Dakota: Omaha, Nebraska, 

Department of the Army, 48 p., 

16 pl. 

For more information, please contact:


District Chief


U.S. Geological Survey


1608 Mt. View Road


Rapid City, SD 57702


(605) 355-4560


For more information on the 1972 flood, please visit the USGS Web site at: 

http://sd.water.usgs.gov/projects/1972flood 

For real-time streamflow data in South Dakota, please visit the USGS Web site at: 

http://sd.water.usgs.gov