Danger - Dam Ahead
Sigrid Pilgrim
Every year people still drown on rivers because they do not recognize the danger a dam poses on an often quiet and slow flowing river or children falling into the water while playing nearby. These dams, many of which no longer serve their intended purpose, continue to degrade the natural river environment and are a hazard to boaters, anglers and other people using rivers for recreational purposes. Often these dams are the only features interrupting a normally slow and quiet moving stream, making boaters believe that the bubbling waters will add a little “whitewater excitement”. However, when water flows over the face of the dam, gravity pulls it towards the bottom of the river causing a depression that needs to be filled by water flowing back upstream which creates the recirculation effect, or a hydraulic. Anyone caught in this recirculation will be pushed down into the water at the face of the dam, then gets pulled back up with the upstream flow of the water towards the dam again, making escape almost impossible without help, especially if the dam stretches across the river, as is often the case. A valuable teaching tool to demonstrate this danger is our Dam Simulator, a 4-foot-long, and 1 foot wide acrylic tank containing a model of a typical, Army Corps of Engineers dam design. A sump pump submerged in a plastic barrel provides a continuous flow of water over the dam and the clear sides offer a powerful demonstration how the water flowing over the dam sets up the recirculation. Little doll house figures or wooden cut-out “people” very visually demonstrate the effects of what actually happens to people caught in the hydraulic below a dam. We have demonstrated our Dam Simulator for many years at paddling and other events. The late Marge Cline took excellent video footage which eventually was combined with actual dam footage videos by Thomas Lindblade after the tragic drowning of three people on the Fox River in Illinois. This eight-minute video, was eventually licensed to the American Canoe Association (ACA) and DVDs can be obtained for a minimal cost. Engineering drawings for the dam were developed by Susan Sherrod, and anyone interested in building a dam simulator can send an email requesting copies of the design drawings me at spconsult@comcast.net. The video has received much praise, including from professionals in the field noting that “it is the best visual example to demonstrate what happens below a dam”. The Dam Simulator can also demonstrate many other river features, such as how to modify a dam to reduce the hydraulic by placing rocks or boulders on the downstream side of the dam; showing foot entrapments when people stand up in moving water and getting feet and legs caught in rocks when water is at a level above their knees; strainers, which are trees or tree branches across the river that can trap a boater or swimmer, and many other river features. Please enjoy our video and share with anyone to help educate about the dangers of dams.
Citation: Pilgrim, S. (2017). Danger - Dam Ahead. In: Avramidis, S. (Ed.). Conference on Near-Death Experiences while Drowning (p. 23). Ft. Lauderdale, Florida, USA: International Swimming Hall of Fame.
