ACA ACA Water Reading & River Hydrology 2 — Questions and Answers
Question 1: What is the International Scale of River Difficulty Class III rating?
- Easy with small waves, suitable for beginners
- Moderate rapids with irregular waves, requiring basic maneuvering skill (Correct answer)
- Advanced whitewater with long, difficult, unavoidable rapids
- Expert-only water with extreme difficulty
Correct 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.
Question 2: What does 'reading water from shore' mean in ACA river instruction?
- Using a topographic map to estimate river difficulty
- Scouting a rapid from land to identify hazards and plan a route before paddling (Correct answer)
- Measuring water depth with a gauge staff
- Checking river flow data online before launching
Correct 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.
Question 3: What is a 'pillow' of water in river hydrology?
- A cushion of water that builds up on the upstream face of a submerged rock (Correct answer)
- A calm flat section between two rapids
- A large standing wave at the base of a drop
- Aerated whitewater at the base of a waterfall
Correct 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.
Question 4: What causes a 'pourover' on a river?
- Water flowing over a completely submerged rock creating a hydraulic below (Correct answer)
- Water cascading down a steep exposed cliff face
- Wind-driven waves rolling over a shallow reef
- Overflow from a dam gate opening
Correct 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.
Question 5: In ACA river instruction, what does 'ferrying' describe?
- Portaging a boat around an unrunnable rapid
- Crossing a current by angling the boat and paddling to move laterally without losing ground (Correct answer)
- Lining a canoe through a technical section with ropes
- Paddling downstream in a straight line through rapids
Correct 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.
Question 6: What is 'flood stage' in the context of ACA river safety instruction?
- Water level exactly at bankfull capacity with safe paddling conditions
- Water level exceeding normal banks, dramatically increasing hazards and current speed (Correct answer)
- The minimum flow level required to paddle a river
- A seasonal low water period exposing rocks
Correct 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.
ACA ACA Water Reading & River Hydrology 2
What is the International Scale of River Difficulty Class III rating?