Upper Letts dam
Upper Letts
Upper Letts is a federal dam located in Stonyford, California, along Letts Creek. Built in 1958 by the USDA Forest Service, this earth dam stands at 21 feet high with a hydraulic height of 26 feet, serving primarily for recreation purposes. With a storage capacity of 319 acre-feet, Upper Letts offers a serene environment for water resource and climate enthusiasts to enjoy various water-related activities.
Despite its small drainage area and uncontrolled spillway type, Upper Letts poses a high hazard potential with a moderate risk assessment rating. Currently, the dam's condition remains unrated, with the last inspection conducted in June 2014 by the Forest Service. While emergency preparedness measures have not been specified, the dam's risk management strategies and inundation maps readiness are unknown, highlighting the need for proactive monitoring and maintenance to ensure the safety of the surrounding community and recreational users.
As part of the San Francisco District, Upper Letts is closely regulated and operated by the Forest Service, emphasizing the importance of continued oversight and adherence to safety guidelines. With its picturesque location and potential risks, Upper Letts serves as a reminder of the delicate balance between utilizing water resources for recreation while safeguarding against potential hazards in the face of changing climate patterns and environmental conditions.
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 Upper Letts -- inflows here typically show up in storage 24-72 hours later.
| Streamgauge | Discharge | View |
|---|---|---|
| Nf Cache C A Hough Spring Nr Clearlake Oaks Ca | 31 cfs | → |
| Nf Cache C Nr Clearlake Oaks Ca | 114 cfs | → |
| Ef Russian R Nr Calpella Ca | 39 cfs | → |
| Ef Russian R Nr Ukiah Ca | 156 cfs | → |
| Russian R Nr Ukiah Ca | 0 cfs | → |
| Kelsey C Nr Kelseyville Ca | 15 cfs | → |
Make a day of it
Boat launches, lakeside camping, fishing access, and other reservoirs near Upper Letts.
⚓ Boat launches
- Lucerne Harbor Park
- Walker Ridge Road Lake County
- Island Drive Lake County
- Lake County
- 3rd Street 20, Lakeport
- Ball Park Avenue 14775, Clearlake
⛺ Campgrounds
More campgrounds →🎣 Fishing spots
- East Park Reservoir
- Lake Pillsbury
- Clear Lake (Lake Cty)
- Lake Mendocino
- Cameron's Fishing Hole Catch & Release
- Black Butte Lake
🛶 Paddle runs
- Headwaters In Sec 28, T18n, R8w To One-Third Mile Beyond Snow Mt. Wilderness Boundary At Private Property Boundary Near Paradise Creek
- North Fork Cache Creek
- Elk Creek
- Cache Creek
- Private Land In Sec 1, T21n, R9w To Confluence Of Cold Creek And Black Butte River
- Deep Hole Creek
Track Upper Letts 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 Upper Letts
Where does the data for Upper Letts 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 Upper Letts.