Hannum Mill Dam

River/Stream: South Skunk River

Location: north of Ames, Story County
        Latitude: 42.068385
        Longitude: -93.619329
        Click here to view an aerial map of the dam.


Owner: U.S. Geological Survey

Height: 3 feet

Length: 50 feet

Hazards: drowning, varying

Warning Signs: standard signs in place

Portage: At Hannum's the portage trail had washed out but there was never a time that one couldn't get through - as had been reported. We quickly rerouted around the wash and later trimmed a couple trees that caused problems for some who carried across and put in the eddy immediately below the dam. -- Rick Dietz

Comments: ruins of very old rock crib mill dam capped with concrete; also known as US / General Filter Dam

Incident Report:

"The accident occurred at what we call the US Filter dam, just north of Ames & almost visible from Hwy 69 opposite Ada Hayden Park. I'd say it's a 3-4 ft drop at most levels. It is obvious as you approach from upstream & is routinely run by canoes, kayaks, and tubers, but for those that choose to use it, there's an EASY portage river-right accross the dam structure itself.

"We're told that the concrete structure caps the original rock-and-crib mill dam, and that the four large timbers sometimes visible on the downstream side are part of the original cribbing. The concrete cap has a sloping downstream surface but does create a small hydraulic at it's base.

"I think it's fair to say that as low-head dams go, most of us never considered this one particularly dangerous. I suspect Tom had run it before on numerous other occasions. I don't know if the hydraulic could have been a factor, but it is easy to imagine someone swamping as they scraped across the dam (the water was relatively low on the 17th) or hit a standing wave or timber at it's base. Capsizes here are not uncommon."

Fatalities 2

  • April 17, 2005 - canoeist Thomas Manatt
  • May 3, 1963 - floater David Barnhart

Overlook of dam from southern bank

Looking downstream over dam horizon line