If you are going downstream by canoe or raft on an unfamiliar river, and there is a waterfall ahead, are you likely to be able to detect the sound and the cloud of spray sufficiently far in advance to reach the river bank before you are swept over the fall? Or are there other warning signs that would be noticeable in advance?

If not, does that mean it is always unsafe to be on a river at high enough altitude that a waterfall is possible, unless you have comprehensive enough information about the river to be sure there isn't one?

  • 11
    It is always unsafe to be on a river you have no map of. This has nothing to do with altitude. Rapids, whirlpools, and other hazards can be as dangerous as a waterfall - or more than a small one - and being stranded somewhere because you have put a hole in your canoe can be fatal. Whether you might notice a waterfall in time just is not the question. Jun 3, 2021 at 12:39
  • 6
    A river doesn't have to be at high elevation to have a deadly waterfall. You're probably picturing plunging over a steep cliff, falling hundreds of feet, and dying from the impact. However, you can also die from a much shorter waterfall, simply by being trapped in the plunge pool by the water currents, and being repeatedly pushed under by the falling water and pulled under by the currents. Such waterfalls can occur on basically any river; it only takes an elevation difference of a few feet.
    – csk
    Jun 3, 2021 at 19:52

5 Answers 5


No. Not reliably. But you only need to be wrong once.

Depending on how abrupt the drop is, you may only see a horizon line, with no white caps from rapids below. If there is enough wind to put riffles on the water, you may not notice it. An abrupt drop will have all the noise hidden below the horizon, so sound will be substantially attenuated.

Factors that increase risk:

  • The current is faster than your back ferry.
  • There is wind that masks the sound of the water.
  • You are preoccupied, chatting, singing old songs from your youth, not paying attention.
  • You are running without good maps.
  • You haven't pre-marked the maps with potential trouble spots.
  • You have no journals from previous trips.
  • High volume rivers are more dangerous. Wider, deeper, faster.

Factors that decrease risk:

  • You have compared the maps to google earth shots, and marked any white water that doesn't show on the maps.
  • You have marked the maps up with notes from log books, journals etc. This can be problematic on long unused routes. E.g. The MacFarlane River, when we did it, we found: One account of the bottom quarter done in 20 years before; one account from the 1930's from a member of the Canadian Geological Survey of the middle half of the river. A mention in Tyrell's book that it was used as a aboriginal route to avoid going up the Athabasca. The upper quarter we had no data but the maps.

Several times, once on the Foster River, once on the Tazin River, once on the Taltson River I have found rapids that were not marked on the map. Certain things, however are triggers. These are not certain, but are "There may be dragons..."

  • A contour line crosses the river.
  • The river narrows to 1/3 of it's previous width.
  • Both shores have rocky outcrops.
  • There is a horizon line on the water -- you see tree tops -- not trunks -- beyond the line.
  • The map changes from 2 parallel lines (showing channel width) to single line. (special case of the previous item)
  • Anytime current is faster than your back ferry.

The Foster River one was the scariest. Decades ago, I don't remember what triggered me, but I called "Running order" (Canoes 50 m apart single file, experienced and less experienced crews alternating.) We crept along the side watching the shore line to gauge our speed vs effort. From 50 meters away it was obvious. We went to shore and scouted.

It was a class VI rapid. The kind that takes canoes and spits out fiberglass toothpicks. Not marked on the map.

Even doing all of the above is no guarantee. I have also found marked rapids that turned out to be nothing at all. When water levels change, some rapids are covered by water backed up at a narrows below, or revealed at lower flow rates. A rapid that is an easy Class II boulder garden at low water, can become III+ hair raising with boiling eddies and whirlpools with another 2 feet of water. Or the same water rise can turn an active rapid into moderate, dull fast water.

This makes wilderness tripping fun.


It's always risky to be on a river that you have no information about.

Apart from waterfalls there could be other dangers such as rapids, rocks under the surface, whirlpools/undercurrents, artificial dams, ...

This isn't like in the movies, where the protagonists float down a calm river on a flimsy boat until they see from afar the misty cloud of a waterfall... There are many possibilities that could lead you into dangerous situations. E.g...

  • the upcoming danger is obstructed from view, or
  • the river turns into a gorge, making it impossible to get out even if you saw the danger ahead of time, or
  • a river flows more strongly and faster, making getting out difficult and dangerous, or
  • an upcoming waterfall/rapid is shaped in a way to make only little sound, giving you only very little advance warning (this happens more often for artificial 'waterfalls', e.g. over dams, etc.),
  • etc...

Bottom line: educated yourself on any body of water you plan on traveling on: read up online, in books, guides, ... ask locals or other people with experience.

If you can't do that be extra cautious, try to look (and think) ahead, and be conservative in your choices and risk taking.

  • 2
    Add tidal situations, for example a river where the the tide has turned and is ebbing faster than you can paddle. It is possible to be carried out to sea before you can reach a shore. Jun 4, 2021 at 18:23

Of course you should research your rivers beforehand, and have a decent idea of where the major hazards are, but even assuming you've done so and are expecting them, it's still necessary to detect the hazards as you approach, and this is something covered in the kayak leader training I've done (I know also canoe leader training is similar, and would expect this to extend to rafting).

Yes, sound usually gives a good warning of waterfalls or rapids ahead, before the horizon line appears. That gives time to scout cautiously, from the bank, the water, or both.

The exceptions are likely to be continuous rapids leading into steeper falls, where the noise of the rapids covers the noise of the falls until late.

Spray is rarely helpful. It's often not very visible from above the falls.

But note that first descents and similar expeditions are far slower than running a well-known river. One reason is the need to scout, or hop from one safe eddy to the next considering escape routes.


You can usually notice the noise. And if the river is loud, then be triple careful.

But generally, it's not important what you notice, but what you don't notice.

Can you see water 100m in front of you? Great, than you know, if the next 100 meters are safe. But you have no idea if the 101 meter is still safe.

Your security margin is as far as you can see. What you can't see, might be a lethal danger. Behind any curve, any rock, there might be a lethal danger. So if you can't see far enough, prepare to go to the shore in every moment.


It is usually much easier to climb up a steep hill, than climb down again. Then you fall and die. It is usually much easier to eel your way into a tight spot than out again. You get stuck, you die.

Similarly, it is much easier to enter a river, than to swim back to shore and climb out of it. You drown and die.

  • Stop.
  • Think.
  • Observe.
  • Pull Out. OR Pursue.

Do not enter a river without knowing where and how it runs. How will you exit? unknown. That is a typical situation to skip observe and go straight to Pull Out...

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