Grap Dam Reservoir Report
Nearby: Cunard Dam Buss Dam
Last Updated: December 14, 2025
Grap Dam, located in Missouri Valley, Iowa, is a privately owned structure designed by the USDA NRCS for the primary purpose of flood risk reduction.
°F
°F
mph
Wind
%
Humidity
Summary
Completed in 2011, this earth dam stands at a height of 29 feet and has a length of 340 feet, providing a storage capacity of 48 acre-feet. The dam also serves multiple purposes including grade stabilization, recreation, and creating a fish and wildlife pond.
With a low hazard potential and a condition assessment of "Not Rated," Grap Dam has not been inspected recently but is still considered to meet safety guidelines. The dam's spillway width is 16 feet, and it has no outlet gates. The structure is not owned or funded by any federal agency, making it a unique example of private ownership for water resource management in the region. Despite not being state regulated, the dam plays a crucial role in managing water flow and mitigating flood risks in the area.
Overall, Grap Dam stands as a testament to effective private ownership and design in water resource management. Its construction and multiple purposes make it a valuable asset for the community, providing not only flood protection but also opportunities for recreation and wildlife habitat enhancement. As climate enthusiasts and water resource advocates, we can appreciate the careful planning and engineering that went into creating this essential infrastructure for the region.
Year Completed |
2011 |
Dam Length |
340 |
Dam Height |
29 |
River Or Stream |
Trib to Willow Creek |
Primary Dam Type |
Earth |
Surface Area |
3 |
Drainage Area |
0.21 |
Nid Storage |
48 |
Outlet Gates |
None |
Hazard Potential |
Low |
Foundations |
Soil |
Nid Height |
29 |
Seasonal Comparison
Weather Forecast
Nearby Streamflow Levels
Boyer River At Logan
|
417cfs |
Soldier River At Pisgah
|
112cfs |
Little Sioux River Near Turin
|
1040cfs |
Monona-Harrison Ditch Near Turin
|
158cfs |
Big Papillion Cr
|
38cfs |
Missouri River At Omaha
|
17700cfs |
Dam Data Reference
Condition Assessment
SatisfactoryNo 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. Note: Rare or extreme event is defined by the regulatory agency based on their minimum
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. Investigations and studies are necessary.
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.
Not Available
Dams for which the condition assessment is restricted to approved government users.
Hazard Potential Classification
HighDams 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, environment 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.
Not Available
Dams for which the downstream hazard potential is restricted to approved government users.
Grap Dam