Tumblesom dam
Tumblesom
Tumblesom is a private fish and wildlife pond located in Lyons, Colorado, along the South St. Vrain Creek. Constructed in 1918, this rockfill dam stands at 19 feet tall and spans 186 feet in length, with a storage capacity of 149 acre-feet. The dam serves multiple purposes, including providing habitat for fish and wildlife, as well as offering recreational opportunities for visitors.
Managed by the Colorado Department of Water Resources, Tumblesom has a low hazard potential and is in satisfactory condition as of the last inspection in October 2020. With a moderate risk assessment rating, the dam is equipped with an uncontrolled spillway and has a maximum discharge capacity of 96 cubic feet per second. While no emergency action plan is currently in place, the dam is regularly inspected every six years to ensure its safety and functionality.
Located in the Omaha District, Tumblesom is overseen by private owners and falls under state jurisdiction for regulation, permitting, inspection, and enforcement. The dam plays a crucial role in supporting the local ecosystem and providing a scenic backdrop for recreational activities, making it a notable water resource and climate enthusiast destination in Boulder County, Colorado.
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 Tumblesom -- inflows here typically show up in storage 24-72 hours later.
| Streamgauge | Discharge | View |
|---|---|---|
| South St. Vrain Creek Near Ward | 37 cfs | → |
| Middle Boulder Creek At Nederland | 104 cfs | → |
| Left Hand Creek Near Boulder | 36 cfs | → |
| Fourmile Creek At Orodell | 2 cfs | → |
| Boulder Creek Near Orodell | 63 cfs | → |
| St. Vrain Creek At Lyons | 89 cfs | → |
Make a day of it
Boat launches, lakeside camping, fishing access, and other reservoirs near Tumblesom.
Boat launches
- Miramonte Road Boulder County
- Lagerman Trail Boulder County
- Boat Launch Grand Lake
- Grand County
- Hilltop Boating Site
- Cr 6 Grand County
Campgrounds
Fishing spots
- Red Rock Lake - Ipwa
- Moraine Lake - Ipwa
- Left Hand Reservoir - Ipwa
- Pony Lake - Ipwa
- Brainard Lake - Ipwa
- Mitchell Lakes - Ipwa
Track Tumblesom 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 Tumblesom
Where does the data for Tumblesom 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 Low 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 Tumblesom.