Just to name two affect the Ohio, indirectly, the Youghiogheny River dam near Confluence PA, the Allegheny dam near Kinzua PA. Dams exist on the other tributaries, the Tennessee River for Example (A tributary of the Lower Ohio)
http://www.lrp.usace.army.mil/nav/ohioback.htmHere is a list of the Lock and Dams in the Pittsburgh District:
http://www.lrp.usace.army.mil/nav/nav.htmMap of the Flood Control dams on the tributaries of the Upper Ohio:
http://www.lrp.usace.army.mil/rec/lakes/damlakes.htm"Pittsburgh District’s 26,000 square miles include portions of western Pennsylvania, northern West Virginia, eastern Ohio, western Maryland and southwestern New York. Our jurisdiction includes more than 328 miles of navigable waterways, 23 navigation locks and dams, 16 multi-purpose flood control reservoirs, 42 local flood protection projects and other projects to protect and enhance the Nation’s water resources, infrastructure and environment. "
Note that is just the upper Ohio. Most Flood control dams are NOT on the Ohio proper, such flood control Dams are all on tributaries, but locks and dams do exist on the Ohio.
One last comment, if you look at the map above, you will see the "Pittsburgh District" comes within 20 miles of Lake Erie. The reason for this is simple, the Great Lakes get very little water from the US. Outside of Michigan, almost all water flows SOUTH. THe reason for this is during the end of the Last Glacier period the Glacier block any flow north, east or west. Water had to flow SOUTH. The Glaciers ended about the area of the Great Lakes. As the Glacier melted, the water flow south increased, making the river beds even deeper. Finally the Great Lakes formed as the Glaciers continued their retreat and broke through to each other and the St Lawrence. Thus the Great Lakes get about 90% of their water from Canada, very little from the US (Outside of Michigan).
What this means is in the Mid east States (Ohio to Minnesota) almost all the area is Drained into the Ohio or the Upper Mississippi (Which drains even parts of Canada west of Superior).