Question

Think critically. Why does an increase in runoff lead to faster rising river levels?

A) Because runoff carries sediment into the river
B) Because runoff increases the river's flow rate
C) Because runoff cools the river water
D) Because runoff decreases the river's depth

Answer 1

An increase in runoff leads to faster rising river levels because it contributes additional water to the river, thereby increasing the flow rate and the volume of water within the river channel.

Step-by-step explanation:

When considering the question of why an increase in runoff leads to faster rising river levels, the correct answer is B) Because runoff increases the river's flow rate. Runoff occurs when excess water from rain or melted snow flows over the land's surface. This can happen quickly, particularly after heavy rainfall or the melting of snow. When this excess water joins a river, it increases the volume of water in the river channel, which leads to higher water levels.

As the river or stream flows away from the source and collects more runoff, its width and volume increase, which causes a modification in the sedimentation pattern. This primarily happens in the lower stretches of a river, where the gradient decreases, and the water moves more slowly, causing sediments carried by the faster-moving water upstream to settle.

Moreover, Environmental Biology states that the steady normal flow of river water is generally from groundwater. However, soon after heavy precipitation, the river discharge sees a significant contribution from surface runoff, thus affecting the river's flow rate and level.