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 submerged rock that causes eddies

Answer

A fast laminar flow channel between rocks

Answer

A calm pool at the bottom of a rapid

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

A downstream current that accelerates boat speed

Answer

A surface wave caused by wind

Answer

A drop in water level indicating a waterfall

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

The width of the river at its widest point

Answer

The temperature change across a river section

Answer

The ratio of flatwater to rapids in a stretch

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 submerged hazard below the surface

Answer

An approaching hydraulic feature

Answer

Shallow water over a gravel bar

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 rock garden requiring technical maneuvering

Answer

A shallow riffle section of a river

Answer

A whirlpool formed by converging currents

Question 6

How does water volume affect river hazard levels as taught in ACA instructor courses?

Accepted Answer

Higher volume increases current speed and hydraulic power, making features more dangerous

Answer

Higher volume always makes rivers safer by washing hazards away

Answer

Volume has no effect on hazard level

Answer

Lower volume always increases danger by exposing more rocks