ACA Water Reading & River Hydrology Flashcards

What is the International Scale of River Difficulty Class III rating?

Answer: Moderate rapids with irregular waves, requiring basic maneuvering skill

Class III on the International Scale indicates moderate, irregular rapids requiring maneuvering skill, but with safe eddies and predictable entry lines.

What does 'reading water from shore' mean in ACA river instruction?

Answer: Scouting a rapid from land to identify hazards and plan a route before paddling

Reading water from shore means physically walking to the bank to visually assess a rapid's hazards, hydraulics, and ideal paddling line before committing to run it.

What is a 'pillow' of water in river hydrology?

Answer: A cushion of water that builds up on the upstream face of a submerged rock

A water pillow is the cushion of upstream-pressing water that builds against the face of a rock, which can deflect a paddler or swimmer away from the obstacle.

What causes a 'pourover' on a river?

Answer: Water flowing over a completely submerged rock creating a hydraulic below

A pourover forms when water flows over a fully submerged rock or ledge, dropping into a hydraulic trough that can recirculate downstream.

In ACA river instruction, what does 'ferrying' describe?

Answer: Crossing a current by angling the boat and paddling to move laterally without losing ground

A ferry maneuver involves angling the boat into the current and paddling to move laterally across the river while the current pushes forward, maintaining position or crossing without losing ground.

What is 'flood stage' in the context of ACA river safety instruction?

Answer: Water level exceeding normal banks, dramatically increasing hazards and current speed

Flood stage means the river has exceeded its normal banks, creating extremely fast currents, widespread strainers, and dangerous submerged obstacles.