Weather Event 
The May 1948 flood in the Clearwater River Basin was caused from snowmelt combined with rainfall events. Cool weather during the early spring months kept snow cover at low elevations hanging around until the middle of May. Cooler than average temperatures and above average precipitation also occurred in the spring months. Above average temperatures began melting the snowpack the middle of May. A rain event on May 22nd caused excessive runoff and a rapid increase in streamflows across the Clearwater River Basin. Warmer weather between May 22-28 continued to increase streamflows due to snowmelt and another rain event on May 28th brought additional flooding that produced a peak on many streams and rivers on May 29. Flooding in the Clearwater River basin continued until about the 11th of June. 

Flood Event 
The flood of May and June 1948 stretched from Idaho to Oregon. After flooding much of the Clearwater River Basin the water traveled downstream and combined with many other tributaries to flood the Columbia River from Washington to Oregon. The Columbia River was running at twice its average spring volume, the river and its equally overflowing tributaries overwhelmed levees and flooded numerous communities and thousands of acres of farmland in British Columbia, Montana, Idaho, Washington, and Oregon. When the water receded in late June, the flood waters killed at least 50 people, caused about $102 million in damages, and spurred interest in building flood control dams on the Columbia River System (Jennifer Ott, August 30, 2013). 

The following tables show how dramatic the 1948 flood was compared to other floods and remains the flood of record for many rivers and streams in the Clearwater River Basin.

Newspaper account of the 1948 flood

Newspaper account of the 1948 flood

Learn More:

• John Harrison, "Floods and Flood Control," Northwest Power and Conservation Council website accessed August 27, 2013
• Richard Nokes, "Vanport City: From a Bog, a 'Zoomtown,'" The Oregonian, March 28, 1943, magazine section, p. 1
• William G. Robbins, Landscapes of Conflict: The Oregon Story, 1940-2000 (Seattle: University of Washington Press, 2004), 71
• William F. Willingham, Army Engineers and the Development of Oregon: A History of the Portland District U.S. Army Corps of Engineers (Washington: Government Printing Office, 1983), 150-159
• "2 Warnings of Floods Given," The Seattle Times, June 1, 1948, p. 3
• "Cross-State Highway is Endangered," The Seattle Times, May 28,1948, pp. 1, 15; "Flood Crumbles Vanport, Thousands Escape Death," The Oregonian, May 31, 1948, p. 1
• "Flooded Roads Are Drying Up," The Seattle Times, June 19, 1948, p. 3
• "Large N.W. Area Swept by Floods," The Seattle Times, May 23, 1948, p. 2
• "Thousands Flee N.W. Homes Before Floods," The Seattle Times, May 27, 1948, p. 1
• Floods of May-June 1948 in Columbia River Basin (Washington: United States Government Printing Office, 1949), 13
• Flood Plain Information Orfoino and Riverside, Idaho Clearwater River prepared by Corps of Engineers, U.S. Army Walla Walla, Washington District May 1968
• Flood Plain Information Orfoino , Idaho Orofino Creek and Whiskey Creek prepared by Corps of Engineers, U.S. Army Walla Walla, Washington District October 1972
• Special Flood Hazard Information Kooskia-Stites, Idaho South Fork Clearwater River prepared by Corps of Engineers, U.S. Army Walla Walla, Washington District June 1974

Unusually cold and wet weather dominated during the spring of 2010. This weather maintained the high elevation snowpack in the west central mountains of Idaho late into the season and kept the ground wet. From June 2-4, a stream of moisture, with origins in the tropical Pacific Ocean, brought 2 to 6 inches of rain to the West Central Mountains. Runoff from rain and snowmelt sent many rivers and creeks out of their banks and reservoir releases were increased to make space for the large runoff inflows. Water releases from Cascade Dam were at a record high.

Widespread flooding occurred along creeks and small tributary rivers in the Payette Basin as well as along the main stem of the Payette River. Flooding also occurred in other areas of central Idaho, including Adams, Idaho, Lewis, and Washington counties. In Valley County, significant flooding occurred on Lake Fork Creek and Gold Fork River. Numerous roads were washed out and several bridges were destroyed. On Lake Fork Creek, an earthen dam associated with Browns Pond collapsed. Several people and animals were rescued during the peak of the flood. People were evacuated from the Gold Fork Hot Springs area along the Gold Fork River.

Main stem river flooding occurred on the South Fork of the Payette River in Boise County and caused minor flooding in Lowman. Flooding along the Payette River was magnified downstream in Gem County and Payette County. Near Emmett, water flooded a portion of State Highway 52 and a county bridge was washed out. Floodwaters impacted railroad tracks, numerous county roads, and caused extensive agricultural flooding. In Payette County, 42 homes and 6 businesses were impacted by floodwaters.

No fatalities occurred. Damage to homes, businesses and roads was estimated at 2.4 million dollars in Payette County. Estimated damage to roads in Valley County was at least 1.3 million dollars. Total public assistance cost estimate for all counties was over 5.3 million dollars (Idaho Severe Storms and Flooding, FEMA-1927-DR).

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Frozen ground + snow + river ice * warm rains & wind = Flood

Impacted: Northern Idaho and North-Central Idaho

Presidential Disaster Declaration for Boundary, Bonner, Kootenai, Shoshone, Benewah, Latah, Nez Perce, Lewis, Clearwater, and Idaho Counties as well as the Nez Perce Tribe. 

Record crests observed on Palouse, Orofino and Lapwai Creeks. The Coeur d'Alene and St Joe Rivers experienced their 2nd highest crests on record during this event.

No fatalities.

At least $30,000,000 of damage to infrastructure and homes.

Significant events/stories
A near-record river crest combined with ice breached several different levee sections in the community of St Maries, ID, resulting in the inundation of over 100 homes, some up to their rooftops. As rivers and creeks began to flood and erode highways and county roads, ingress/egress to several regions was cut off and many communities had to be evacuated. Helicopters airlifted several residents to safety in the Coeur d'Alene River basin and other rescues were undertaken in boats and atvs. As the Coeur d'Alene River was rising, residents of Cataldo continued to build an emergency sandbag dike, even after the National Guard was pulled out for safety reasons. The river eventually broke through the sandbag dike, flooding Cataldo and forcing the evacuation of its residents. The outlet dam on Winchester Lake was overtopped and the dam nearly failed. Downstream of the dam, record flows on Lapwai Creek overtopped the Culdesac levee and forced the evacuation of a portion of the town. In total, several hundred homes and dozens of businesses experienced severe flood damage. Several homes were completely destroyed. A summary of the event can be found at theIdaho State Mitigation Plan (Section 3.3 - Flood)

Floodwaters behind St Maries levees

 

Disastrous spring flooding occurred on the Snake River in eastern Idaho from March 14 to June 30, 1997, primarily due to the rapid melt of a record high snowpack at high elevations, and heavy rains in late May and early June. The flood impacted the upper to middle Snake River from below Palisades Reservoir to American Falls Reservoir in eastern Idaho and prompted a Presidential and FEMA Disaster Declaration for these eastern Idaho counties: Bingham, Bonneville, Butte, Custer, Fremont, Jefferson, and Madison.

During the winter of 1996 to 1997, the upper Snake River Basin received a significant amount of snowfall; snowpack exceeded 250 percent of normal in some of the higher elevations. By May, the snowpack in the higher elevations along the Continental Divide started to produce above normal snowmelt. The Bureau of Reclamation began increasing water releases from Palisades Reservoir to accommodate the impending snowmelt from the winter’s accumulation. In late May, heavy rains resulted in rapid snowmelt and subsequent runoff. By June 11, the flows coming out of the reservoir coupled with high tributary discharges produced the highest flows on the Snake River since 1918. Along the Snake River stretch, downstream of Palisades Dam to American Falls Dam, record crests were observed at five streamgage locations. Three other locations on this reach experienced their second highest crest in observed history.

At its peak, the Snake River flooded as far as a mile from its banks and many places were inundated by 5 feet of water. On June 16, flood fights were conducted on the Snake River at Roberts, where voluntary evacuations were in effect. River levels nearly overtopped existing flood control levees, and flooding of agricultural lands began far from the main channel as irrigation canals overflowed their banks. Numerous county roads and state highways were closed due to floodwaters and damage to bridges, especially in Jefferson County. These road closures had a significant impact on transportation and flood response activities. On June 17, flood fighting efforts continued in several small towns, including Menan, Firth, Blackfoot, and Labelle. On June 18, Interstate 15 was closed for nearly 20 miles between Shelley and Blackfoot. The state estimated that approximately 500 people were displaced from their homes in Jefferson and Bingham Counties. Agricultural officials estimated that more than 50,000 acres of farm, pasture, and cropland had been flooded; 30,000 in Bingham County alone.

No known flood fatalities or injuries resulted, although two Idaho Army National Guardsmen died in a helicopter crash supporting the flood relief efforts.
Flood damages were estimated to be over $4 million. Relief totaled $11,365,667 in public assistance, $8,054 in individual assistance, $251,054 from the NRCS, and $1,691,458 in hazard mitigation grants. 

On July 7, 1997, six counties in Southeastern Idaho (Bingham, Bonneville, Custer, Fremont, Jefferson, and Madison) were added to five northern counties already declared under FEMA Disaster Declaration DR-1177. On July 25, Butte County was also declared.

Flood aerial view, June 18, 1997

Flooded building

Interstate 15 crossing Snake River near the city of Blackfoot, Idaho

South Twin bridge collapse (between Archer and Ririe, Idaho)

Point graphical representation of yearly highest peaks in observed history

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The Teton Dam was constructed from February 1972 to June 1976 in the Teton River Canyon in Fremont County, Idaho. The dam was earthen filled and stood approximately 305 feet above the riverbed and was about 3,200 feet long at its crest. The reservoir behind the dam was about 17 miles long when full and contained 260,000 acre-feet of water. The dam was about 13 miles northeast of the city of Rexburg and 10 miles east of Sugar City.

This flood marker, inside the National Aquarium at Baltimore's Inner Harbor, is a reminder of the extreme flooding Isabel brought to the region

The reservoir behind the newly constructed dam was filled for the first time ig the spring of 1976. On Thursday, June 3, water began seeping from the canyon wall about 750 feet downstream from the dam. By early Saturday, June 5, a new leak had appeared near the right abutment. Late Saturday morning, a whirlpool developed in the reservoir above the dam and the hole on the downstream side had grown to more than 25 feet in diameter. The dam collapsed at 11:57 am, unleashing a torrent of water down the Teton River Valley. The reservoir drained in less than 6 hours with a maximum discharge from the dam estimated at 2.3 million cubic-feet per second.

The flood wave tore through downstream communities including Sugar City and Rexburg, and then traveled down the Snake River Valley causing major flooding in communities along the Snake River. The flood wave crest reached the city of Blackfoot during the early morning hours on Monday, June 7. Officials were concerned that American Falls Reservoir would not be able to hold the floodwaters, but in the end the American Falls Dam held.

Sugar City and surrounding areas were hardest hit by the Teton Dam collapse. Floodwaters made numerous roads impassable, homes were swept off foundations, vehicles, farm equipment, machinery, and livestock were washed away. Hundreds of farms, homes, and businesses were damaged or destroyed. In Idaho Falls, water was up to 4 feet deep in the western part of the city. Evacuations ahead of the floodwaters forced thousands of people into shelters and emergency housing.

The flood caused 11 deaths and near $2 billion in damage.

Advancing floodwaters (unknown photographer)	Floodwaters in downtown Rexburg (unknown photographer)

Teton Dam collapse (Photos: Bureau of Reclamation)

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