Flooding in the High Desert
Mesa County, Colorado
Flooding in the High Desert
At first glance, Mesa County may seem like an unlikely place for flooding. It's desert landscape and dry climate do not immediately conjure up images of high water events. Perhaps you may have never seen floodwaters in Western Colorado! But be aware- even if you have never seen a flood, it doesn’t mean that it hasn’t happened before or won’t happen again! Water is a powerful force or nature. While it provides vitality for humans and ecosystems alike, it also poses a risk to lives and property. It is important to understand your flood risk and know how to act in the event of an emergency.
Mesa County - Living up to It's Name
Mesa County is located in Western Colorado and is named after the many mesas – flat topped ridges formed from tectonic uplift and erosion.
Mesa Rock Formation.
Grand Junction is the largest city in Mesa County and is located at the confluence of two major rivers - the Colorado River and the Gunnison River, hence the name Grand Junction. Zoom in and click around on the map to learn more about Mesa County.
Mesa County, Colorado
The Colorado River: A Vital Resource
The Colorado River Drainage Basin is over 39,000 square miles and intersects seven states and Mexico. The river is roughly 1,450 miles long. Its main stem originates in the Southern Rocky Mountains in Colorado. Smaller tributaries feed into the main stem before the entire system drains into the Gulf of California. The Colorado River also runs through significant land marks like Lake Powell, the Grand Canyon, Moab, Lake Mead, and Baja California. The Colorado River gets its water from snowmelt in the higher elevations and rain events.
The Colorado River (Image courtesy of: U.S. Army Corps of Engineers)
All streams in Mesa County are either direct or indirect tributaries to the Colorado River. A tributary is a river or stream that flows into a larger river or lake. The three largest tributaries of the Colorado River that flow through Grand Junction are the Gunnison, Dolores, and San Miguel Rivers.
There are also several smaller creeks and washes that flow into the Colorado River and are potential flooding sources. A wash is a dry, shallow creek, stream, or gulch that seasonally fills with water. Washes can be dangerous during flash floods as they can quickly fill and convey water downstream.
Explore the map on the right to learn more about the bodies of water that flow through Mesa County! Try zooming in to see all the smaller bodies of water, including several washes. Clicking on the river and streams (shown in blue) will provide information about their annual flow rates. The charts show the average monthly flow for each body of water. The units are in cubic feet/second. A cubic foot is roughly the size of a basketball. Think of the flow as how many basketballs pass by a certain cross section of the river in a second!
Compare these statistics to your own experience with rainfall in Mesa County. Flooding is most likely to happen when flows are high, and this often correlates with summer thunderstorms and snowmelt runoff.
Another Grand Canyon
Gunnison River. (Image courtesy of: Wikipedia)
The Gunnison River is the largest tributary of the Colorado River at 180 miles long. It feeds into Colorado River at a Junction in Grand Junction, hence the City’s name. The Gunnison River is formed by the junction of two tributaries; the Taylor River and the East River. Pictured is the Black Canyon of the Gunnison, which is one of the most narrow and deepest gorges in the world. The Gunnison River is primarily snowmelt fed. During years with particularly heavy snowfall, the Gunnison often has equal flow volume as the Colorado River. In fact, almost 70% of the Colorado’s flow is fed by the Gunnison River.
One of the Many Tributaries
Dolores River. (Image courtesy of: Google Earth)
The Dolores River is another tributary of the Colorado. It is prone to flooding both from snowmelt runoff and rainfall events. The Dolores River is approximately 241 miles long and originates in the San Juan National Forest in Colorado, and runs through the south western portion of Mesa County. Check out the map to follow the course of the Dolores River!
Smaller Washes Have Mighty Forces
Mesa County is at risk from flooding, primarily from the Colorado River and the Gunnison, although several creeks and washes can pose significant flood risk. Major streams within Mesa County include:
- Red Star Canyon
- Gold Star Canyon
- Little and Big Salt Wash
- Bosley Wash
- Hunter Wash
- Adobe Creek
- Kannah Creek
- Indian Creek
- Plateau Creek
- Callow Creek
- Douglas Wash
A Climate for Flooding
Mesa County is located in the Basin and Range and has an arid, high elevation climate. Much of the County’s climate is influenced by the vastly varying topographic features. Precipitation and snow primarily fall at high elevations.
Snow accumulates in the high country, serving as a natural reservoir for water storage. In the low-lying valley, the climate is often dry and arid, and receives little rainfall compared to the mountainous areas of the County.
Rainfall patterns vary greatly from year to year, but generally rainfall is greatest in the springtime and early fall. Snow accumulates in the mountains during winter months. Warm air eventually melts the snow accumulation, leading to an influx of water entering waterways in spring and summer.
Flooding Science. (Image courtesy of: NOAA)
Why Does Flooding Happen in the Desert?
Flooding in Mesa County is primarily driven by snowmelt runoff. Snowmelt runoff occurs when warm temperatures or precipitation melts the snow in high elevation. The melted snow then flows downhill into existing rivers and streams. If the snow melts very quickly or if there is a large volume of runoff, it causes the river to rise very quickly which often results in flooding. Flooding in primarily occurs in May, June, and July as the warm summer temperatures melt the snow in high elevations.
Rainstorms (also called cloudburst storms) also contribute to the flooding hazard in Mesa County. As large amounts of rain fall, it can quickly overfill rivers, streams, and washes in the lower elevations.
Las Vegas Flood 1984. (Image Courtesy of: Clark County Flood Control District)
Las Vegas, one of the most famous desert towns, has experienced large floods in the past from rainstorms that cause dangerous flash floods. The Regional Flood Control District has built 661 miles of canals and 102 detention basins to work to reduce the flood risk to this desert community.
Las Vegas Strip near Caesar’s Palace 1999. (Image Courtesy of: National Weather Service)
Historical Flooding Accounts
Mesa County has a long history of flooding. There are written records of flooding in the area since the mid 1800's. Since then, numerous floods have occurred throughout the county. Often, documentation of historic floods in sparsely documented. Be aware, just because there isn’t a comprehensive documented record of flood damages, doesn’t mean flooding hasn’t happened or won’t happen again! In fact, there is nearly a 100% chance of flooding on any given year.
On the Colorado River, there have been seven major historical flood events which occurred in 1884, 1920, 1921, 1935, 1952, and 1957.
The Gunnison River has four major floods documented in 1884, 1920, 1921, and 1957.
The Dolores River has documented flood events in 1884, 1909, 1911, and 1958. The 1958 flood incurred an estimated $230,000 in damages.
Recent flooding events have occurred in Mesa County in 1986, 2006, and 2013.
Photo is of a previous a previous flood in Frutta. Photo Courtesy of Robert Grant.
“So Mighty A Stream”
The earliest noted reference to high water on the Colorado River is contained in a journal kept by George H. Heapin the spring of 1853.
June 23. We continued down its right bank [Gunnison River] until we reached Grand [Colorado] River. We had been prepared to find Grand River swollen, for its tributaries were all at their highest stage of water; but we had not anticipated so mighty a stream. It flowed with a loud and mighty current, its amber-colored water roaring sullenly past, laden with the wrecks of trees uprooted by their fury. Where we now stood, anxiously gazing at its flood it had spread to a breadth of 250 yards.
Photo Courtesy of Wikipedia.
Impacting the Way of the West
Flooding was widespread in Mesa County in 1884. May 1884, temperatures in Mesa County quickly warmed up to about 70-80 degrees and warmer nights, which caused a rapid melting of the high elevation snowpack. The runoff flowed into the Gunnison River, causing the river to rise and swell. Later that month, heavy rains cased the river to continue flooding. The Denver & Rio Grande Railroad was forced to shut down service through July 1884, because a train had been stalled in up to 3 feet of water. Additionally, a bridge near Escalante collapsed as a trained passed over it, sadly several lives were lost.
Photo is taken from the 1911 flood in Durango of the Denver & Rio Grande Railroad line that was damaged in another flood event.
Across the West, railroads were constantly impacted by flooding, as was no exemption in Mesa County. Many railroads followed riverways and impacts from flooding could cause major distributions to transportation and the delivery of vital supplies.
Photo Courtesy of Durango Herald.
Costly Floods in the 1950's
In the summer of 1957, heavy rains melted snow in the high elevations, causing flooding from snow melt runoff. Approximately 4,000 acres in Mesa County flooded and damage totaled $430,000 or $3.8 million in 2020 dollars.
Again in 1958, roughly 1,100 acres in the Gateway area flooded from both snow melt runoff and heavy cloudburst storms. The estimated damage to the lands was $230,000, which is over $2 million in today’s dollars!
Flooding continues to pose a costly threat to communities! Across the nation, flooding costs the United States roughly $4.6 billion dollars per year in damages and rehabilitation (NOAA, 2020).
Destructive Flood of 1983
According to the County's Hazard Mitigation Plan, "The most recent serious floods on the Colorado River occurred in 1983 and 1984. Peak flows on the Colorado River at the State Line were approximately 61,000 and 70,000 cfs in 1983 and 1984 respectively. Colorado River flood flows in the Grand Junction area inundated streets, lawns, and gardens; deposited sand, silt, and debris; and flooded basements and lower floors in residential areas in the Riverside Park, Rosevale and Connected Lakes area southwest of the City in 1983 and 1984 but has not caused significant damage since these events. The flooding events in 1984 resulted in loss of life as did the flooding event that occurred on I-70 when Bosley Wash flooded in [2006] resulting in a drowning."
An article on this event can be found on the New York Times:
Oral Histories
Flooding is a powerful force of nature that will happen time and time again. Check out the Mesa County Library link to look through historical resources that document flooding in and around Mesa County.
Bosley Wash
The nature of the Bosley Wash Watershed and the conveyance leads to infrequent, but occasionally severe, flood events. The watershed consists of 3.3 square miles of highly varied terrain including, rural, semi-urban, and desert mountain environments. There are steep, unimproved channels originating on the slopes of the Bookcliffs and Mt. Garfield north of I-70, this part of the Bosley Wash channel is relatively unimproved landscape with an undefined channel allowing for sheet flow across the rugged landscape. The Bosley Wash project focuses on the greatest potential for losses in the community by reducing the flood risk and the loss of life that is present with the current drainage system.
There are various extreme storm events that impacted Bolsey Wash and the residence that live in this watershed, including two intense rain events during the summer of 1999, each were represented as high intensity storm events with a recurrence interval in the range of the 100-yr storm event. In August 2006, a death on I-70 was ruled as a drowning due to the mud and debris flow that was washing across the highway after heavy rains that flooded the area. There have been additional flood events prior to and after the death on I70, that made Bosley Wash a primary focus for Mesa County.
Bosely Wash flooding in August 2014.
In 2013 after the floods that occurred on the Front Range, allowed for federal funding to become available state wide for flood control projects. Mesa County applied for Federal and State funding in 2014 and was awarded funding for the project in 2015.
Flooding at Bosley Wash in 2014.
In 2018, Mesa County undertook construction of the Bosely Wash Detention Pond near Mount Garfield to prevent any future loss of life from flooding events. The project is designed to protect against a 100 year flood event, or a flood that has a 1% of occurring in any given year. The $2.2 million project costs were split between FEMA (75%), the State of Colorado (12.5%), and Mesa County (12.5%).
Bosley Wash Detention Basin Under Construction.
County officials examine the newly constructed Bosely Wash Detention Basin.
Orchard Mesa Detention Basin
Orchard Mesa is located near the confluence of the Colorado and Gunnison Rivers in Grand Junction, Colorado. The area has been developed for residential and commercial uses, and its drainage system was designed to handle irrigation flows. Heavy flooding in the area in 2013 showed that the drainage system was grossly inadequate for conveying stormwater.
To better prepare for flooding and to protect the lives and property in Orchard Mesa, Mesa County applied for a Hazard Mitigation Grant from FEMA for the design and construction of Veterans Memorial Detention Pond project in 2014. The project was designed to intercept storm flows along the Highway 50 flow path and release it at a reduced rate to better control flooding. Walking trails were included around the pond and the wetland areas, along with viewing areas for public education purposes, picnic tables and benches, and additional landscaping was added to the southern section area to provide for sports fields and community events.
The Veterans Memorial Detention Pond not only reduces flood risk, but also provides trails and landscaping for the community to use.
The Veterans Memorial Detention Pond project accomplished all goals of reducing potential losses of life and property by collecting and reducing the 100- year storm event, along with reducing sediment and debris within the Orchard Mesa main drain system. The project was completed within the original $1.2 million budget and within the modified grant deadline. All involved in the project, including Mesa County Facilities Department and the Public Works Engineering staff worked closely together to meet the needs of both departments and to accomplish a successful project that not only addresses stormwater issues but provided a new parks facility for Mesa County residents.
Wetlands at the Veterans Memorial Detention Pond where some water is diverted to. Wetlands offer many ecosystem benefits and help reduce flood risk!
Preparedness Links
Flooding is an unstoppable force. It is a natural process that offers many benefits for riverine ecosystems. But, as human populations continue to grow and develop, floodplains are being paved over and constructed on. While flood measures like dams or levees can help reduce flooding risk to humans, they do not eliminate the risk altogether.
To protect yourself and your loved ones, it is important to understand your flood risk. Check out the map below to identify the flood risk in your neighborhood.
FEMA Mapped Flood Hazard Areas
Below are resources to help you and your family prepare for a flood. Important steps to take include developing and practicing a personal emergency action plan, have a go bag ready, and obtaining FEMA flood insurance.
