The Big Thompson River is a

tributary A tributary, or affluent, is a stream or river that flows into a larger stream or main stem (or parent) river or a lake. A tributary does not flow directly into a sea or ocean. Tributaries and the main stem river drain the surrounding drai ...

of the

South Platte River The South Platte River is one of the two principal tributaries of the Platte River. Flowing through the U.S. states of Colorado and Nebraska, it is itself a major river of the American Midwest and the American Southwest/ Mountain West. It ...

, approximately 78 miles (123 km) long, in the U.S. state of

Colorado Colorado (, other variants) is a state in the Mountain states, Mountain West subregion of the Western United States. It encompasses most of the Southern Rocky Mountains, as well as the northeastern portion of the Colorado Plateau and the wes ...

. Originating in Forest Canyon in Rocky Mountain National Park, the river flows into

Lake Estes Lake Estes is a reservoir in Estes Park, Colorado created by Olympus Dam. The lake has a shoreline of about and a surface area of . The reservoir lies on the Big Thompson River The Big Thompson River is a tributary of the South Platte River ...

in the town of

Estes Park Estes Park is a statutory town in Larimer County, Colorado, United States. The town population was 5,904 at the 2020 United States Census. Estes Park is a part of the Fort Collins, CO Metropolitan Statistical Area and the Front Range Urban Cor ...

and then through Big Thompson Canyon. It includes four crossings/bridges which are listed on the U.S. National Register of Historic Places.

Course of the river

The headwaters of the Big Thompson River begin in Forest Canyon within Rocky Mountain National Park in Larimer County, Colorado. The river flows east through Moraine Park to the town of

. There it is held in

Olympus Dam Olympus Dam is a dam located on the Big Thompson River, in the town of Estes Park, Colorado Estes Park is a statutory town in Larimer County, Colorado, United States. The town population was 5,904 at the 2020 United States Census. Estes Park i ...

before being released into the Big Thompson Canyon. The North Fork Big Thompson River also begins in Rocky Mountain National Park, on the northern slopes of the Mummy Range. This tributary flows east, through the town of Glen Haven, where it merges with the Big Thompson River in the town of

Drake Drake may refer to: Animals * A male duck People and fictional characters * Drake (surname), a list of people and fictional characters with the family name * Drake (given name), a list of people and fictional characters with the given name * ...

, in the Big Thompson Canyon. From Lake Estes, the river descends 1/2 mile (800 m) in elevation through the mountains in the spectacular 25 mi (40 km) Big Thompson Canyon, emerging from the foothills west of Loveland. It flows eastward, south of Loveland across the

plains In geography, a plain is a flat expanse of land that generally does not change much in elevation, and is primarily treeless. Plains occur as lowlands along valleys or at the base of mountains, as coastal plains, and as plateaus or uplands. In ...

into

Weld County Weld County is a county located in the U.S. state of Colorado. As of the 2020 census, the population was 328,981. The county seat is Greeley. Weld County comprises the Greeley, CO Metropolitan Statistical Area, which is included in the Denver ...

and joins the South Platte approximately 5 mi (8 km) south of Greeley. It receives the

Little Thompson River The Little Thompson River is a tributary of the Big Thompson River and thence the South Platte River in the U.S. state of Colorado. The river's headwaters lie in the Roosevelt National Forest. It flows east through the foothills of the Rocky Mou ...

approximately four mi (6 km) upstream from its mouth. Water resources in the Big Thompson River are managed by the

Northern Colorado Water Conservancy District The Northern Colorado Water Conservancy District — more commonly referred to as Northern Water — is a water utility for eight counties in northeastern Colorado. Northern Water works with the Colorado-Big Thompson Project to transfer water from ...

as part of the Colorado-Big Thompson Project.

1976 flood

On July 31, 1976, during the celebration of Colorado's centennial, the Big Thompson Canyon was the site of a devastating flash flood that swept down the steep and narrow canyon, claiming the lives of 143 people, 5 of whom were never found. This flood was triggered by a nearly stationary

thunderstorm A thunderstorm, also known as an electrical storm or a lightning storm, is a storm characterized by the presence of lightning and its acoustic effect on the Earth's atmosphere, known as thunder. Relatively weak thunderstorms are some ...

near the upper section of the canyon that dumped 300 millimeters (12 inches) of rain in less than 4 hours (more than 3/4 of the average annual rainfall for the area). Little rain fell over the lower section of the canyon, where many of the victims were. 1976 Big Thompson Flood Memorial

Around 9 p.m., a wall of water more than 6 meters (20 ft) high raced down the canyon at about 6 m/s (14 mph), destroying 400 cars, 418 houses and 52 businesses and washing out most of U.S. Route 34. This flood was more than 4 times as strong as any in the 112-year record available in 1976, with a discharge of 1,000 cubic meters per second (35,000 ft³/s). In 2008, a man who was thought to have died in the flood was found to be alive and living in Oklahoma. Daryle Johnson and his family had rented a cabin east of Estes Park, but left without telling anyone on the morning of July 31. A woman who was researching the flood's victims discovered he was still alive.Flood 'Victim' Found Alive 32 Years Later
, TheDenverChannel.com. 2008. Big Thompson Canyon, Colorado

2013 flood

The canyon was just one of the many areas along the Front Range that were devastated in the September 2013 flood. While not as intense as the 1976 flood, the storms that caused the flooding in 2013 still sent enough water down the canyon to wash out the highway in many places. The flood also damaged the US Bureau of Reclamation's Dille Diversion Dam. The biggest infrastructure casualty, however, was the City of Loveland's hydroelectric plant (rebuilt after the 1976 flood); the Idylwilde Reservoir was completely filled with silt and rocks, the Idylwilde Dam broke free of the bedrock, and the hydroelectric plant in the Viestenz-Smith Mountain Park was filled with water and silt. The dam was in the process of being relicensed with the FERC, but it was instead demolished, the dam material and contents of the reservoir being used as fill for highway repairs. The park has since been redone to accommodate the post-flood river channel and to harden it against potential future floods. The city also rebuilt its municipal electric distribution line into the canyon to replace the original 1925 transmission line and remove obsolete distribution equipment.

References

External links

I Dream of Genealogy Memorial for Big Thompson Canyon Flood Victims of 1976

Colorado State University: Big Thompson Watershed

Northern Colorado Water Conservancy District

{{Authority control Tributaries of the Platte River Rivers of Larimer County, Colorado Rivers of Weld County, Colorado 1976 natural disasters in the United States 1976 in Colorado 1976 floods Rivers of Rocky Mountain National Park

Course of the river

1976 flood

2013 flood

See also

References

External links