Williston Mill Dam (Md 617 Old Harmony Road) dam
Williston Mill Dam (Md 617 Old Harmony Road)
Located in Williston, Maryland, the Williston Mill Dam, also known as Todds Mill Pond, is a privately owned structure that serves primarily for recreation purposes. Constructed in 1936, this earth dam stands at a height of 18 feet and spans a length of 630 feet along Mill Creek. With a storage capacity of 585 acre-feet, this dam plays a role in regulating the flow of water and providing a surface area of 51.6 acres for recreational activities.
Managed by the Maryland Dam Safety agency, the Williston Mill Dam has a low hazard potential and is currently rated as "Not Rated" in terms of condition assessment. Despite its relatively low risk level, the dam is subject to regular state inspections and enforcement to ensure its safety and functionality for the surrounding community. With a maximum discharge capacity of 1660 cubic feet per second and a controlled spillway design, the dam is equipped to handle potential excess water flow in a controlled manner.
While the Williston Mill Dam may not pose a significant risk currently, its location within a high-risk area highlights the importance of ongoing risk management measures. With a very high risk assessment score of 1, it is crucial for the dam owners and regulatory agencies to continue monitoring and maintaining the structure to prevent any potential incidents or emergencies. For water resource and climate enthusiasts, the Williston Mill Dam serves as a fascinating example of how human-made structures can both enhance recreational opportunities and play a crucial role in water management within local ecosystems.
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 Williston Mill Dam (Md 617 Old Harmony Road) -- inflows here typically show up in storage 24-72 hours later.
| Streamgauge | Discharge | View |
|---|---|---|
| Marshyhope Creek Near Adamsville | 22 cfs | → |
| Tuckahoe Creek Near Ruthsburg | 37 cfs | → |
| Choptank River Near Greensboro | 47 cfs | → |
| Nanticoke River Near Bridgeville | 31 cfs | → |
| Sallie Harris Creek Near Carmichael | 3 cfs | → |
| Beaverdam Branch At Houston | 0 cfs | → |
Make a day of it
Boat launches, lakeside camping, fishing access, and other reservoirs near Williston Mill Dam (Md 617 Old Harmony Road).
Track Williston Mill Dam (Md 617 Old Harmony Road) 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 Williston Mill Dam (Md 617 Old Harmony Road)
Where does the data for Williston Mill Dam (Md 617 Old Harmony Road) 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 Williston Mill Dam (Md 617 Old Harmony Road).