Holly dam
Holly
Holly, located in Arapahoe County, Colorado, serves as a critical flood risk reduction structure along Little Dry Creek. Built in 1979, this earth dam stands at a height of 40 feet and spans 1170 feet, providing a storage capacity of 455 acre-feet. Despite being classified with a high hazard potential, the dam's condition assessment was rated as satisfactory during the last inspection in November 2018.
Managed by local government authorities, Holly is regulated by the Colorado Department of Water Resources with state permitting, inspection, and enforcement in place. With a spillway width of 200 feet and uncontrolled spillway and outlet gates, this structure plays a vital role in mitigating flood risks for the surrounding area. While the dam's risk assessment is moderate, ongoing risk management measures are not explicitly documented.
For water resource and climate enthusiasts, Holly presents a fascinating case study in dam infrastructure and flood risk management. Its strategic location, design features, and regulatory oversight highlight the complex interplay between human interventions and natural forces in safeguarding communities against water-related hazards. As efforts continue to ensure the structure's safety and effectiveness, Holly stands as a testament to the ongoing challenges and opportunities in sustainable water resource management.
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 Holly -- inflows here typically show up in storage 24-72 hours later.
| Streamgauge | Discharge | View |
|---|---|---|
| Big Dry Creek Blw C-470 At Highlands Ranch | 2 cfs | → |
| Cherry Creek Below Cherry Creek Lake | 22 cfs | → |
| Harvard Gulch At Colorado Blvd. | 0 cfs | → |
| South Platte River Below Union Ave | 38 cfs | → |
| Harvard Gulch At Harvard Park | 2 cfs | → |
| South Platte River At Englewood | 104 cfs | → |
Make a day of it
Boat launches, lakeside camping, fishing access, and other reservoirs near Holly.
Boat launches
- Cherry Creek Park Road Centennial
- West Quincy Avenue Denver
- Chatfield Lake North Boat Ramp
- Fisherman's Trail Lakewood
- C-470 Trail Lakewood
- West 69th Avenue 4700, Westminster
Campgrounds
- Chief Ouray Group Site
- Cherokee Group Site
- Arapahoe Group Site
- Cherry Creek State Park
- Chatfield State Park
- Bear Creek Lake Park
Fishing spots
- Cherry Knolls Pond
- Little`S Creek Pond
- Gallup Reservoir
- Ketring Lake
- Progress Park Pond
- Cherry Creek Reservoir
Track Holly 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 Holly
Where does the data for Holly 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 Holly.