South Anna Dam #4 dam
South Anna Dam #4
South Anna Dam #4, also known as Allen Lake, is a local government-owned structure in Louisa, Virginia, designed by USDA NRCS and Virginia DCR. Completed in 1981, this Earth-type dam stands at a height of 32 feet and stretches 830 feet in length, with a storage capacity of 2100 acre-feet. Its primary purpose is flood risk reduction along the TR-SOUTH ANNA river. The dam is state-regulated, with inspections and enforcement carried out by the Department of Conservation and Recreation.
Despite being assessed as in fair condition during the last inspection in March 2019, South Anna Dam #4 has a high hazard potential, highlighting the importance of regular monitoring and maintenance. The dam's Emergency Action Plan (EAP) was last revised in January 2013, indicating the need for updated emergency protocols. With a drainage area of 4.27 square miles and a surface area of 20 acres, this dam plays a crucial role in managing water resources and mitigating flood risks in the region.
As a significant infrastructure for flood risk reduction in Louisa, Virginia, South Anna Dam #4 serves as a vital asset for water resource and climate enthusiasts. Its design, construction, and regulatory oversight by state agencies underscore the importance of sustainable water management practices. Continued attention to maintenance and emergency preparedness will ensure the continued efficacy of this dam in safeguarding the community from potential hazards.
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 South Anna Dam #4 -- inflows here typically show up in storage 24-72 hours later.
| Streamgauge | Discharge | View |
|---|---|---|
| Rivanna River At Palmyra | 79 cfs | → |
| N F Rivanna River Near Earlysville | 25 cfs | → |
| Rapidan River Near Ruckersville | 108 cfs | → |
| Hardware River Bl Briery Run Nr Scottsville | 19 cfs | → |
| Robinson River Near Locust Dale | 43 cfs | → |
| Moormans River Near Free Union | 11 cfs | → |
Make a day of it
Boat launches, lakeside camping, fishing access, and other reservoirs near South Anna Dam #4.
Boat launches
- South Boston Road 3315, Fluvanna County
- River Anne Palmyra
- Columbia Road Columbia
- Boat Landing Lane Buckingham County
- River Trail Powhatan County
- Powhatan State Park Road Powhatan County
Campgrounds
- Christopher Run Campground
- Lake Anna State Park
- Westview On The James
- Girl Scout Camp
- Loft Mountain - Shenandoah National Park
- Loft Mountain Campground
Fishing spots
- Bealers Ferry Boat Launch
- Bealers Ferry Pond Accessible Fishing Site
- Moody Boat Launch
- Batzell Boat Launch
Track South Anna Dam #4 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 South Anna Dam #4
Where does the data for South Anna Dam #4 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 South Anna Dam #4.