Seasons & safety
Strainers, Low-Head Dams, and the Hazards That Actually Kill Paddlers
Most people picture the danger of rivers as big whitewater. But on the flat and Class I–II water where casual paddlers spend their time, the things that actually injure and kill are quieter — and more avoidable once you know them.
Strainers
A strainer is anything that lets water through but not you: a fallen tree, a brush pile, a fence. The current flows through and pins whatever it catches against it — and can hold you underwater. Strainers are especially common on the outside of bends and after floods. Avoid them entirely. If you’re swept toward one, don’t try to fend off with your feet — swim aggressively over it, climbing on top rather than being pulled under.
Low-head dams
Low-head dams are short, uniform walls across a river, often only a few feet high. Water pouring over creates a recirculating hydraulic at the base that pulls objects back into the falling water and holds them there. They’re nearly impossible to escape and have earned the name drowning machines. They look benign from upstream, which is what makes them deadly. Portage every dam — get out well above and carry around. Many of our section notes flag specific dams to portage.
Cold water
Cold water incapacitates faster than most people believe — cold shock and rapid loss of strength. Dress for the water temperature, not the air. See the spring runoff guide.
Foot entrapment
Never stand up in moving water above knee depth. If your foot wedges between rocks and the current pushes you over, you can be held face-down. If you swim a rapid, float on your back, feet up and pointed downstream, until you reach calm water.
How to stay clear of all of them
- Scout blind bends and anything you can’t see over.
- Portage dams — always.
- Wear your PFD, carry a whistle, and paddle with others.
- Avoid rivers that are high, rising or full of debris — read the conditions guide.
These four hazards are the core of the safety guide. Learn to see them and you’ve handled the biggest risks in casual paddling.
Frequently asked
What is a strainer in a river?
A strainer is an obstacle — usually a fallen tree or brush — that lets water flow through but stops solid objects like a boat or a person. Current pins you against it and can hold you underwater. Avoid strainers at all costs.
Why are low-head dams so dangerous?
Water going over a low-head dam creates a recirculating hydraulic (a “keeper”) at the base that traps and holds swimmers and boats. They look harmless but are called “drowning machines.” Always portage around them.
Remember: verdicts and guides are informational only. Always scout, wear a PFD, and check local conditions. Read the safety guide.