Tappan Dam is an earth dam located in Harrison County, Ohio, built in 1936. It carries a High hazard potential classification.
Dam profile
NID height · 52 ft52 ft tall and 1,550 ft long, taller than 93% of U.S. dams with a recorded height. Height is drawn to scale against a ten-story building, about 100 ft; the profile is a generic embankment section and the water level is illustrative.
About Tappan Dam
The primary purpose of Tappan 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 USACE - Huntington District (federal). It impounds the Little Stillwater Creek near Dennison.
The dam stands 52 feet tall and stretches 1,550 feet across, creates a reservoir covering 2,350 acres, has a maximum storage capacity of 61,600 acre-feet, and collects water from a drainage area of 71 square miles. Completed in 1936, the structure is well-established, with more than 75 years of service.
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. An emergency action plan is in place for this dam. The most recent inspection on record was 04/04/2024.
At 52 feet, this dam is taller than 93% 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 Ohio 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 | Ohio |
| County | Harrison |
| Nearest City | Dennison |
| River/Stream | Little Stillwater Creek |
| Coordinates | 40.35888, -81.22664 |
Physical Characteristics
| Dam Type | Earth |
| NID Height | 52 ft |
| Dam Length | 1,550 ft |
| Year Completed | 1936 (90 years old) |
Storage & Hydraulics
| NID Storage | 61,600 acre-ft |
| Max Storage | 61,600 acre-ft |
| Normal Storage | 35,100 acre-ft |
| Surface Area | 2,350 acres |
| Drainage Area | 71 sq mi |
| Max Discharge | 23,700 cfs |
| Spillway Type | Uncontrolled |
Ownership & Safety
| Purpose | Flood Risk Reduction |
| Owner | USACE - Huntington District |
| Owner Type | Federal |
| Hazard Classification | High |
| Condition Assessment | Not assessed |
| Last Inspection | 04/04/2024 |
| Emergency Action Plan | Yes |
Identifiers
| NID ID | OH00010 |
| Federal ID | OH00010 |
| More Info | State Dam Safety Program |