Flatiron dam
Flatiron
Flatiron, also known as Afterbay, is a federal-owned dam located in Larimer County, Colorado. Constructed in 1953 by the Bureau of Reclamation, this earth dam stands at a height of 86 feet, with a primary purpose of hydroelectric generation and irrigation. With a storage capacity of 1,136 acre-feet, Flatiron serves as a crucial water resource for the region.
Situated on Dry Creek-Tr and Chimney Hollow Creek, Flatiron plays a key role in managing water flow and storage in the area. The dam has a surface area of 381,500 square feet and drains an area of 7.42 square miles. Despite its high hazard potential, with a risk assessment rating of 2, Flatiron is regulated and inspected by the Bureau of Reclamation to ensure its structural integrity and safety.
For water resource and climate enthusiasts, Flatiron represents a significant infrastructure for water management in Colorado. With its hydroelectric capabilities and role in irrigation, this dam serves as a vital component of the region's water supply system. As a federally-owned and regulated structure, Flatiron plays a crucial role in safeguarding the surrounding communities from water-related risks and emergencies.
Dam data reference
Condition Assessment
- Satisfactory
- No existing or potential dam safety deficiencies are recognized. Acceptable performance is expected under all loading conditions (static, hydrologic, seismic) in accordance with the minimum applicable state or federal regulatory criteria or tolerable risk guidelines.
- Fair
- No existing dam safety deficiencies are recognized for normal operating conditions. Rare or extreme hydrologic and/or seismic events may result in a dam safety deficiency. Risk may be in the range to take further action.
- Poor
- A dam safety deficiency is recognized for normal operating conditions which may realistically occur. Remedial action is necessary. POOR may also be used when uncertainties exist as to critical analysis parameters which identify a potential dam safety deficiency.
- Unsatisfactory
- A dam safety deficiency is recognized that requires immediate or emergency remedial action for problem resolution.
- Not Rated
- The dam has not been inspected, is not under state or federal jurisdiction, or has been inspected but, for whatever reason, has not been rated.
Hazard Potential Classification
- High
- Dams assigned the high hazard potential classification are those where failure or mis-operation will probably cause loss of human life.
- Significant
- Dams assigned the significant hazard potential classification are those dams where failure or mis-operation results in no probable loss of human life but can cause economic loss, environmental damage, disruption of lifeline facilities, or impact other concerns. Significant hazard potential classification dams are often located in predominantly rural or agricultural areas but could be in areas with population and significant infrastructure.
- Low
- Dams assigned the low hazard potential classification are those where failure or mis-operation results in no probable loss of human life and low economic and/or environmental losses. Losses are principally limited to the owner's property.
- Undetermined
- Dams for which a downstream hazard potential has not been designated or is not provided.
Plan around the weather
Same NOAA / yr.no feed Snoflo's iOS app uses. Watch the precipitation column on the meteogram -- rain on the basin upstream typically lifts inflow 24-72 hours later.
Next 5 days, hour by hour
Temperature line with weather symbols on top, snow + rain accumulation as columns, humidity as a dotted line.
5-day forecast table
Every 3 hours, broken out across temperature, snow, rain, humidity, and wind. Each cell is colour-coded relative to the column min/max.
| Time | Condition | Temp (°F) | Snow (in) | Rain (in) | Humidity (%) | Wind (mps) | Wind dir |
|---|---|---|---|---|---|---|---|
| Loading detailed forecast… | |||||||
15-day temperature & precipitation
Daily temperatures, snow, and rain projected over the next two weeks.
Nearby streamflow gauges
USGS streamgauges around Flatiron -- inflows here typically show up in storage 24-72 hours later.
| Streamgauge | Discharge | View |
|---|---|---|
| Buckhorn Creek Near Masonville | 21 cfs | → |
| Big Thompson River At Loveland | 73 cfs | → |
| St. Vrain Creek At Lyons | 69 cfs | → |
| Cache La Poudre R Ab Boxelder C | 226 cfs | → |
| Cache La Poudre River At Fort Collins | 237 cfs | → |
| Left Hand Creek At Hover Road Near Longmont | 2 cfs | → |
Make a day of it
Boat launches, lakeside camping, fishing access, and other reservoirs near Flatiron.
Boat launches
- Boat Ramp Larimer County
- Lagerman Trail Boulder County
- Filter Plant River Access Point (Put-In)
- Pineview River Access Point (Put-In, Take-Out)
- Bridges River Access Point (Put-In)
- Bridges River Access Point (Take-Out)
Campgrounds
- Flatiron Reservoir
- Carter Lake - North Side Campgrounds
- North Pine Campground
- Pinewood Reservoir
- Carter Lake - South Side Campgrounds
- Boyd Lake State Park
Fishing spots
- Flatiron Reservoir
- Carter Lake
- Pinewood Reservoir
- Lon Hagler Reservoir
- Boedecker Reservoir
- Lonetree Reservoir
Paddle runs
Track Flatiron in the Snoflo app
Save this dam as a favorite and get the local NOAA / yr.no forecast plus regional flow context wherever you are.
About Flatiron
Where does the data for Flatiron come from?
Structural and regulatory data come from the U.S. Army Corps of Engineers' National Inventory of Dams (NID). Weather forecast comes from NOAA / yr.no -- the same feed Snoflo's iOS app uses.
How often is the report updated?
NID structural data refreshes annually as the Corps publishes updated assessments. The weather forecast refreshes throughout the day.
What does the High hazard rating mean?
The Corps of Engineers' hazard potential classification grades probable consequences if the dam fails: High = probable loss of human life; Significant = no probable loss of human life but possible economic loss / environmental damage; Low = no probable loss of human life, only minor economic / environmental losses. See the Dam Data Reference card above for the full definitions.
What's "% of normal"?
The current storage value compared to the historical average storage on this calendar day. 100% = right on average; values above 100% mean above-normal storage (wet year); values below mean below-normal (dry year or drought).
Can I get alerts when storage crosses a threshold?
Yes -- alerts are managed in the Snoflo iOS app. Favorite this dam, set a threshold, and you'll get a push the moment conditions cross.
Other water bodies near here
Snoflo-tracked reservoirs and dams within driving distance of Flatiron.