Exam 14: Streams and Floods: the Geology of Running Water

What is a flash flood? Suggest two circumstances that might lead to flash flooding.

What is runoff?

What kind of drainage network is likely to form in a landscape characterized by a parallel series of ridges and valleys?

Geologists are trying to determine the discharge of a river.The stream is semicircular in shape with a width of 10 m and depth of 5 m.They measure the velocity of the river to be 0.2 m/s.What is the discharge of the river? Sketch this cross-section,and show your work.Recall that the area of a circle is πr²,and a semicircle is one-half of that.

If a 50-year flood occurs on the Mississippi River this year,what is the probability that a flood of the same magnitude will occur in the following year?

Describe some of the methods that have been used for flood control,and explain why these methods have limitations or do not always work.

Ephemeral streams ________.

In the picture below,fragments of bed load bounce along the bed and knock other grains up into the flow to move downstream for short distances.This process is called

Which landscape feature is most likely to form a drainage divide?

The base level of a tributary would ________ if a dam and a reservoir were constructed where it flowed into a trunk stream.

What kind of drainage network is likely to form in a landscape with a uniform substrate and a constant and gentle slope at the surface?

A parallel drainage network such as the one shown below develops on a very steep slope.What type of geologic processes can be inferred from the presence of a parallel drainage network?

Repeated flooding outside a stream channel and across an entire floodplain can result in a pair of low ridges on either side of a stream termed

Which river has the greatest discharge of any stream on the Earth?

Ultimately,the base level of a stream valley cannot be lower than ________.

Describe what happens to the amount and grain size of sediments carried by a stream when it transitions from high flow velocity to lower velocity.Give an example of where on a landscape such a transition could occur.

What shape does the longitudinal profile of a typical stream follow? A longitudinal profile plots elevation of a streambed with distance,showing the streambed elevation from its highest point upstream to the lowest point at base level.

What physical property of the underlying rock would lead to the formation of a cliff over which a waterfall may form?

Why do deltas form?

Recent tectonic uplift or a drop in base level can result in downcutting into a landscape that had previously been eroded close to base level,in a process called