Big Thompson River
Encyclopedia
The Big Thompson River is a tributary
of the South Platte River
, approximately 78 miles (123 km) long, in the U.S. state
of Colorado
.
in Larimer County, Colorado
. The river flows east through Moraine Park
to the town of Estes Park
. There it is held in Lake Estes by the Olympus Dam 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
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
into Weld County
and joins the South Platte approximately 5 mi (8 km) south of Greeley
. It receives the Little Thompson River
approximately 4 mi (6 km) upstream from its mouth.
Water resources in the Big Thompson River are managed by the Northern Colorado Water Conservancy District as part of the Colorado-Big Thompson Project
.
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
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.
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.
Tributary
A tributary or affluent is a stream or river that flows into a main stem river or a lake. A tributary does not flow directly into a sea or ocean...
of the South Platte River
South Platte River
The South Platte River is one of the two principal tributaries of the Platte River and itself a major river of the American Midwest and the American Southwest/Mountain West, located in the U.S. states of Colorado and Nebraska...
, approximately 78 miles (123 km) long, in the U.S. state
U.S. state
A U.S. state is any one of the 50 federated states of the United States of America that share sovereignty with the federal government. Because of this shared sovereignty, an American is a citizen both of the federal entity and of his or her state of domicile. Four states use the official title of...
of Colorado
Colorado
Colorado is a U.S. state that encompasses much of the Rocky Mountains as well as the northeastern portion of the Colorado Plateau and the western edge of the Great Plains...
.
Course of the river
The headwaters of the Big Thompson River begin in Forest Canyon within Rocky Mountain National ParkRocky Mountain National Park
Rocky Mountain National Park is a national park located in the north-central region of the U.S. state of Colorado.It features majestic mountain views, a variety of wildlife, varied climates and environments—from wooded forests to mountain tundra—and easy access to back-country trails...
in Larimer County, Colorado
Larimer County, Colorado
Larimer County is the seventh most populous and the ninth most extensive of the 64 counties of the State of Colorado of the United States. The county is located at the northern end of the Front Range, at the edge of the Colorado Eastern Plains along the border with Wyoming...
. The river flows east through Moraine Park
Moraine Park Museum and Amphitheater
The Moraine Park Museum and Amphitheater, also known as the Moraine Park Lodge and the Moraine Park Visitor Center, are located in Moraine Park, a glaciated meadow between two moraines in Rocky Mountain National Park....
to the town of Estes Park
Estes Park, Colorado
Estes Park is a town in Larimer County, Colorado, United States. A popular summer resort and the location of the headquarters for Rocky Mountain National Park, Estes Park lies along the Big Thompson River. Estes Park had a population of 5,858 at the 2010 census...
. There it is held in Lake Estes by the Olympus Dam before being released into the Big Thompson Canyon. The North Fork Big Thompson River
North Fork Big Thompson River
The North Fork Big Thompson River is a tributary of the Big Thompson River in Larimer County, Colorado. The river's source is Rowe Glacier on the north slope of Hagues Peak, in the Mummy Range of Rocky Mountain National Park. It flows through Lake Dunraven, over Lost Falls and through Glen Haven...
also begins in Rocky Mountain National Park, on the northern slopes of the Mummy Range
Mummy Range
The Mummy Range is a mountain range in the Rocky Mountains of northern Colorado in the United States. The range is a short subrange of the Front Range located in southwestern Larimer County northwest of the town of Estes Park...
. This tributary flows east, through the town of Glen Haven
Glen Haven, Colorado
Glen Haven is an unincorporated town and a U.S. Post Office in Larimer County, Colorado, United States. The Glen Haven Post Office has the ZIP Code 80532.-Geography:...
where it merges with the Big Thompson River in the town of Drake
Drake, Colorado
Drake is an unincorporated town in Larimer County, Colorado. A U.S. Post Office is also situated near Rocky Mountain National Park in the county. The population of Drake was 219. The Drake Post Office has the ZIP Code 80515.-Geography:...
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
Loveland, Colorado
Loveland is a Home Rule Municipality that is the second most populous city in Larimer County, Colorado, United States. Loveland is situated north of the Colorado State Capitol in Denver. Loveland is the 14th most populous city in Colorado. The United States Census Bureau that in 2010 the...
. It flows eastward, south of Loveland across the plains
Great Plains
The Great Plains are a broad expanse of flat land, much of it covered in prairie, steppe and grassland, which lies west of the Mississippi River and east of the Rocky Mountains in the United States and Canada. This area covers parts of the U.S...
into Weld County
Weld County, Colorado
As of the census of 2000, there were 180,936 people, 63,247 households, and 45,221 families residing in the county. The population density was 45 people per square mile . There were 66,194 housing units at an average density of 17 per square mile...
and joins the South Platte approximately 5 mi (8 km) south of Greeley
Greeley, Colorado
The City of Greeley is a Home Rule Municipality that is the county seat and the most populous city of Weld County, Colorado, United States. Greeley is located in the region known as Northern Colorado. Greeley is situated north-northeast of the Colorado State Capitol in Denver. According to the...
. It receives the Little Thompson River
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 Mountains in Larimer County through the town of Berthoud,...
approximately 4 mi (6 km) upstream from its mouth.
Water resources in the Big Thompson River are managed by the Northern Colorado Water Conservancy District as part of the Colorado-Big Thompson Project
Colorado-Big Thompson project
The Colorado-Big Thompson Project is a water diversion project in Colorado designed to collect West Slope mountain water from the headwaters of the Colorado River and divert it to Colorado's Front Range and plains...
.
Big Thompson Canyon Flooding of 1976
On July 31, 1976, during the celebration of Colorado's centennial, the Big Thompson Canyon was the site of a devastating flash floodFlash flood
A flash flood is a rapid flooding of geomorphic low-lying areas—washes, rivers, dry lakes and basins. It may be caused by heavy rain associated with a storm, hurricane, or tropical storm or meltwater from ice or snow flowing over ice sheets or snowfields...
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
Thunderstorm
A thunderstorm, also known as an electrical storm, a lightning storm, thundershower or simply a storm is a form of weather characterized by the presence of lightning and its acoustic effect on the Earth's atmosphere known as thunder. The meteorologically assigned cloud type associated with the...
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.
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
U.S. Route 34
U.S. Route 34 is an east–west United States highway that runs for 1,122 miles from north-central Colorado to the western suburbs of Chicago. Through Rocky Mountain National Park it is known as the Trail Ridge Road where it reaches 12,183 ft , making it the highest paved through highway in...
. 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.