Shell Rock Milldam dam
Shell Rock Milldam
Shell Rock Milldam, located in Shell Rock, Iowa, is a rockfill dam constructed in 1928 for recreational purposes along the Shellrock River. This local government-owned structure stands at a height of 7 feet and has a storage capacity of 229 acre-feet, with a normal storage level of 152 acre-feet. The dam spans 221 feet in length and covers a surface area of 45 acres in Butler County, Iowa.
Managed by the Iowa Department of Natural Resources, Shell Rock Milldam is regulated, permitted, inspected, and enforced by state authorities to ensure its safety and compliance with regulations. Despite being classified as having a low hazard potential, the dam is considered to have a moderate risk level, with a risk assessment score of 3. The last inspection of the dam was conducted in September 1989, and its condition is currently rated as "Not Rated."
For water resource and climate enthusiasts interested in exploring the intersection of dam infrastructure and environmental conservation, Shell Rock Milldam offers a unique insight into the management of recreational water structures in rural Iowa. With its picturesque location along the Shellrock River, this dam serves as a vital recreational resource for the local community while also highlighting the importance of maintaining and monitoring dam safety in the face of changing environmental conditions and regulatory requirements.
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 Shell Rock Milldam -- inflows here typically show up in storage 24-72 hours later.
| Streamgauge | Discharge | View |
|---|---|---|
| Shell Rock River At Shell Rock | 1,070 cfs | → |
| Cedar River At Waverly | 448 cfs | → |
| West Fork Cedar River At Finchford | 517 cfs | → |
| Cedar River At Janesville | 1,050 cfs | → |
| Beaver Creek At New Hartford | 254 cfs | → |
| Cedar River At Cedar Falls | 3,220 cfs | → |
Make a day of it
Boat launches, lakeside camping, fishing access, and other reservoirs near Shell Rock Milldam.
Boat launches
- Atlas Avenue Bremer County
- Adams Parkway Waverly
- Finchford Road Black Hawk County
- 140th Street Bremer County
- 245th Street Butler County
- Big Lake Loop Cedar Falls
Campgrounds
- Shell Rock Rec Area
- Cedar Bend Park
- Thunder Woman Park
- North Cedar Park
- Black Hawk County Park
- Big Woods Lake
Fishing spots
Track Shell Rock Milldam 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 Shell Rock Milldam
Where does the data for Shell Rock Milldam 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 Shell Rock Milldam.