North Branch Ralston Creek Dam
North Branch Ralston Creek Dam is an earth dam located in Johnson County, Iowa, built in 1983. It carries a High hazard potential classification and has a satisfactory condition assessment.
About North Branch Ralston Creek Dam
The primary purpose of North Branch Ralston Creek Dam is flood risk reduction. The dam is designed to control downstream flooding by temporarily storing excess water during storms and releasing it at a controlled rate. The dam is owned by City Of Iowa City (local government). It impounds the N. Br. Ralston Cr. near Iowa City.
The dam stands 37 feet tall and stretches 590 feet across, has a maximum storage capacity of 1,016 acre-feet, and collects water from a drainage area of 2 square miles. Completed in 1983, the structure is 43 years old.
This dam carries a high hazard potential classification, which means that a failure or uncontrolled release of water would likely cause loss of human life. This classification reflects the consequences of failure, not the likelihood — it indicates that people live or work in the area downstream. Its condition is rated satisfactory, indicating no existing or potential dam safety deficiencies are recognized. An emergency action plan is in place for this dam. The most recent inspection on record was 10/17/2024.
At 37 feet, this dam is taller than 84% of dams nationwide.
Living Downstream
If you live or work downstream of this dam, consider taking these steps: learn your local evacuation routes, check whether your county emergency management office has a dam failure inundation map, and sign up for local emergency alerts. The Iowa dam safety program can provide more specific information about emergency planning for this structure.
Search for dams near your address to see all dams in your area with hazard classifications and safety data.
Location
| State | Iowa |
| County | Johnson |
| Nearest City | Iowa City |
| River/Stream | N. Br. Ralston Cr. |
| Coordinates | 41.67000, -91.51020 |
Physical Characteristics
| Dam Type | Earth |
| NID Height | 37 ft |
| Dam Height | 37 ft |
| Dam Length | 590 ft |
| Year Completed | 1983 (43 years old) |
Storage & Hydraulics
| NID Storage | 1,016 acre-ft |
| Max Storage | 1,016 acre-ft |
| Drainage Area | 2 sq mi |
| Spillway Type | Uncontrolled |
Ownership & Safety
| Purpose | Flood Risk Reduction |
| Owner | City of Iowa City |
| Owner Type | Local Government |
| Hazard Classification | High |
| Condition Assessment | Satisfactory |
| Last Inspection | 10/17/2024 |
| Emergency Action Plan | Yes |
Identifiers
| NID ID | IA02249 |
| Federal ID | IA02249 |
| More Info | State Dam Safety Program |