Marble Rock Milldam dam
Marble Rock Milldam
Marble Rock Milldam, located in Floyd County, Iowa, along the Shell Rock River, was completed in 1913 for the primary purpose of recreation. This gravity dam stands at a height of 15 feet with a length of 187 feet, creating a reservoir with a storage capacity of 836 acre-feet. The dam is state-regulated by the Iowa Department of Natural Resources, ensuring that it meets safety and environmental standards.
Despite being classified as having a low hazard potential, Marble Rock Milldam has a moderate risk assessment rating. While the dam has not been inspected since 1989 and is currently not rated in terms of its condition assessment, it remains a popular spot for recreational activities such as fishing, boating, and picnicking. The dam also serves as a reminder of the region's history and the importance of managing water resources in a sustainable way.
As an important landmark in the area, Marble Rock Milldam continues to attract visitors and water resource enthusiasts who appreciate its historical significance and its role in providing recreational opportunities. With its picturesque location and serene surroundings, the dam serves as a reminder of the intersection between human development and environmental stewardship, prompting discussions about the importance of maintaining and monitoring water infrastructure for future generations to enjoy.
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 Marble Rock Milldam -- inflows here typically show up in storage 24-72 hours later.
| Streamgauge | Discharge | View |
|---|---|---|
| Cedar River At Charles City | 531 cfs | → |
| Little Cedar River Near Ionia | 232 cfs | → |
| Winnebago River At Mason City | 338 cfs | → |
| Shell Rock River At Shell Rock | 1,240 cfs | → |
| Cedar River At Waverly | 1,650 cfs | → |
| West Fork Cedar River At Finchford | 539 cfs | → |
Make a day of it
Boat launches, lakeside camping, fishing access, and other reservoirs near Marble Rock Milldam.
Boat launches
- 245th Street Butler County
- 140th Street Bremer County
- Big Blue Loop Mason City
- South Pierce Avenue Mason City
- Atlas Avenue Bremer County
- Adams Parkway Waverly
Campgrounds
- West Idlewild County Park
- Cedar View Park Campground
- Colwell County Park Camping
- North Cedar Park
- Wilkinson Pioneer Ounty Park Campgrounds
- Osage Sprink Park Campground
Paddle runs
Track Marble 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 Marble Rock Milldam
Where does the data for Marble 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 Marble Rock Milldam.