ACA ACA Water Reading & River Hydrology

Question 1

What is a 'hydraulic' (also called a 'hole') in river hydrology?

Accepted Answer

A recirculating feature where water flows back upstream after dropping over an obstacle

Answer

A hydraulic or hole forms when water drops over a ledge or rock and recirculates back toward the feature, creating a powerful backwash.

Question 2

What is the function of an 'eddy' in river paddling?

Accepted Answer

A calm, upstream-flowing area behind an obstacle used for resting or scouting

Answer

An eddy is a calm pocket of water that flows upstream behind rocks or other obstacles, used by paddlers to rest, regroup, or scout downstream.

Question 3

What does the term 'gradient' mean in river classification?

Accepted Answer

The vertical drop per horizontal distance, usually measured in feet per mile

Answer

Gradient describes how steeply a river drops, expressed in feet per mile, and is a primary factor in determining current speed and rapid intensity.

Question 4

According to ACA water reading instruction, what does a 'V' shape pointing downstream on the river surface indicate?

Accepted Answer

A clear channel of deeper, faster water between obstacles

Answer

A downstream-pointing 'V' on the water surface marks a tongue of clear water flowing between obstacles, indicating the preferred entry line into a rapid.

Question 5

What is 'strainer' as taught in ACA river hydrology?

Accepted Answer

Debris such as branches or logs through which water flows but a paddler cannot pass safely

Answer

A strainer is any obstruction like logs, wire fences, or debris that allows water to flow through but traps and can pin a swimmer or boat against it.

(ACA) American Canoe Association Instructor Certification Practice Test

(ACA) American Canoe Association Instructor Certification Practice Test

ACA ACA Water Reading & River Hydrology