Flash floods: the first rule of canyoning

Almost everything else in canyoning is a matter of skill you can build. The flash flood is different: it is the hazard that experience alone cannot defeat, because by the time you can act, it may already be too late. Understanding it is the price of admission to the sport.

Why canyons flood so fast

A canyon is, by definition, a funnel. Rain that falls across a wide catchment upstream is gathered into a single narrow channel — the one you are standing in. A storm you cannot see, several kilometres away, can send a wall of water down a gorge that is bone-dry where you stand. The rise can take minutes, and the narrow walls give you nowhere to go.

Reading the warning signs

If you are already in a canyon, learn the signals that water is rising and act on the first of them, not the third:

• The water suddenly turns brown or cloudy.
• Twigs, leaves or debris begin floating past.
• The flow rises or the current strengthens noticeably.
• A low rumble grows from upstream.
• The water level climbs against a rock you were watching.

The discipline that prevents it

The real defence happens before you ever reach the canyon. Check the forecast for the entire upstream catchment, not just your location. Treat any unsettled or unstable weather as a reason to cancel. Know your escape points along the route. And accept the hardest part of the sport: turning back. A canyon you walked away from will still be there next week. The discipline to cancel a perfect-looking day because of a storm forty kilometres away is what separates old canyoneers from unlucky ones.