Streams and Floods The Geology Ch14 Test Questions & Answers

CHAPTER 14: Streams and Floods: The Geology of Running Water

LEARNING OBJECTIVES

14A. Explain how streams and drainage networks form and evolve.

14B. Describe the processes that lead to erosion and deposition by streams.

14C. Characterize the changes that take place along the length of a stream from its headwaters to its mouth.

14D. Sketch the evolution of meanders in a stream, and explain the concept of a floodplain.

14E. Distinguish between slow-onset floods and flash floods, and describe the conditions that lead to each.

14F. Describe the various methods that engineers may use to protect areas from flooding, and interpret statements concerning flood frequency.

14G. Characterize environmental issues associated with streams.

MULTIPLE CHOICE

1. A stream is ________.

2. Water in a stream flows from its _________ to its __________.

3. What is runoff?

4. The main stream that is supplied by all tributaries within a drainage network is termed a ________ stream.

5. 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?

6. What kind of drainage network is likely to form in a landscape where the bedrock is broken by a regularly-spaced grid of joints and fractures?

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

8. A radial drainage network is likely to indicate a current or former _______ in the landscape.

9. What kind of drainage network is likely to form in a landscape characterized by a uniform and steep slope and a relatively weak substrate?

10. Over time, a stream tends to increase in length by eroding and extending its channel upstream, in a process called ________.

11. Ephemeral streams ________.

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

13. What is the term for the land area drained by all of the streams that empty into a tributary?

14. The largest drainage basin in the United States drains into the:

15. A trellis drainage network such as the one shown below is most like to form in landscapes develop on which type of geologic structure(s) or feature(s)?

16. 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?

17. In an ephemeral stream, the groundwater table lies _________ the streambed.

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

19. A stream carrying sediment flows over the solid rock of its channel, polishing the rock and wearing it away. This is an example of __________.

20. Running water dissolves soluble minerals. This material is most likely to be transported by a stream as _________.

21. In some cases, the push of flowing water cause large particles to bounce or roll along a streambed. These pieces are then carried along the bottom of the stream as _________.

22. 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

23. The discharge of a river traveling through a temperate region will typically ________ downstream; the discharge of a river traveling through an arid region will typically ________ downstream.

24. A geologist finds an old report on stream discharge and reads a value of “20”, but the rest of the page is cut off. Which of the following could be the appropriate value and units for the discharge of a stream?

25. The average velocity of water in a stream

26. Which of the following is most likely to make up the suspended load of a stream?

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

28. The flat-lying area surrounding a river channel is termed the ________.

29. If over time a stream experiences a decrease in its base level or increase in discharge, a(n) ________ is likely to form.

30. Braided streams ________.

31. The shape of a delta is primarily determined by ________.

32. A “bird’s foot” delta such as the Mississippi River delta forms when the ________.

33. 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.

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

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

36. The distinction between a valley and a canyon is ________.

37. Why do deltas form?

38. The deepest part of a curved stream channel, where the flow is fastest, is called the ________.

39. Meandering streams ________.

40. 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

41. What is a point bar?

42. A meander that is cut off to become completely isolated from the main channel but which retains water is called a(n) ________.

43. Which of the following is MOST likely to result in stream rejuvenation?

44. Which of the following conditions would cause the largest stream capacity?

45. 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

46. Which of the following scenarios is more likely to cause a flash flood than a slow-onset flood?

47. Which of the following best describes a “100-year flood”?

48. 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?

49. Urbanization of a watershed is most likely to result in __________.

50. Runoff from farm fields entering a stream system is likely to be __________ than that from naturally vegetated fields.

1. Using the image below, label the stream channel, meander, floodplain, headwaters, and mouth. Additionally, sketch a cross-section of this stream from A to A' and from C to C'.

2. 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.

3. 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.

4. Differentiate between dissolved load, suspended load, and bed load.

5. Contrast the gradient of a typical stream at its headwaters versus its mouth. Sketch the longitudinal profile of a typical stream.

6. Sketch a meandering stream in map view. Your drawing should include (labeled) the channel, floodplain, meanders, and at least one oxbow lake. How does an oxbow lake form?

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

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

9. Two 100-year floods can occur in two consecutive years. Use the concept of recurrence interval to explain how this is possible.

10. What are some of the ways that urbanization can change how stream discharge responds to rainfall and runoff and affect flooding?