Quiz # 1 Chapters 1 and 2

Practice Questions for Lecture 13 – 14 Streams and Groundwater Geology 1200 KEY

Use these questions to test your knowledge of Lecture 13 - 14.

A. Short answer:

1. Each year, erosion is responsible for the removal of an estimated 3.5 million metric tons of rock from the continents.

2. Hydraulic lifting occurs as a turbulent stream flows through fractures in rock .

3. Abrasion and hydraulic lifting are more (efficient, powerful, energetic) in fast, turbulent streams than in slow ones.

4. A graded stream responds instantaneously to any change in sediment load or discharge in such a way as to establish a new graded state.

5. Every stream carries water from a watershed that is separated from other watersheds by a drainage divide.

6. In a curved section of a stream channel, the fastest water is near the outside of the curve.

7. In a straight section of a stream channel, the fastest water is in the center of the channel just below the surface.

8. In a curved section of a stream channel, the slowest water is near the inside of the curve.

9. In a point bar deposit, the lowermost sediments are course particles from the stream bed. B. Match the Terms.

1. abrasion__m___ a. heavy sediment load

2. point bar deposit__i__ b. steep stream meets broad flat valley

3. saltation__l__ c. water table dropped.

4. floodplain __j__ d. characteristic of karst

5. gradient __o_ e. erosion and deposition equilibrium

6. alluvial fan __b__ f. ability to carry sediment

7. braided stream __a___ g. flow between pores

8. capacity__f___ h. volume space between grains

9. graded stream___e__ i. meandering stream

10. base level__n__ j. submerged during floods

11. Porosity __h__ k. groundwater recharge

12. Permeability __g__ l. bouncing

13. Disappearing stream __d__ m. scrape stationary rocks

14. Collapse sinkhole __c__ n. lowest possible erosion

15. Infiltration __k__ o. slope of streambeds

16. Competence ___p___ p. largest particle carried. C. True or False? Circle the correct answer. Some of these are from your reading.

1. A stream’s base level is the lowest level to which a stream can erode its channel. True or False?

2. A graded stream is one in which an equilibrium has been reached so that there is little net erosion or deposition. True or False? 3. After a sudden increase in sediment load in one area, a stream’s local gradient increases, as does stream velocity. True or False?

4. During a flood, a stream’s power to erode its channel increases dramatically. The increase in erosional power is proportional to the square of the increase in velocity. True or False?

5. Stream piracy occurs when one stream captures the headwaters of another stream on the opposite side of a drainage divide. True or False?

6. The stream that erodes through its divide to capture the other slope drainage does so because of its steeper slope, greater discharge, and less resistant streambed rocks. True or False?

7. Braided streams are caused by an exceptionally low sediment load. True or False? In particular, braided streams have very high bed load and intermittent flow.

8. Streams develop meanders because erosion occurs on the outside (cutbank) of curves, where water velocity is highest, while bar deposition occurs on the inside of curves, where water velocity is lowest. The result is greater channel curvature. True or False?

9. Alluvial fans are formed on low-land plains, while deltas are formed in a standing body of water. True or False?

10. Waterfalls tend to migrate downstream and become larger as erosion wears away their edge. True or False?

11. Streams that disappear into sinkholes are a sure sign of karst land. True or False? 12. Most caves are formed by subsurface dissolution of granite. True or False?

13. Grading (leveling) of steep slopes can enhance groundwater recharge because such a measure reduces the runoff of rainwater. True or False?

14. A perched water table is a water table found on top of a local impermeable layer lying above the zone of saturation. True or False?

15. A water table’s configuration (its underground depth) is usually random and unpredictable. True or False?

16. The greatest infiltration of surface waters would be on steep slopes. True or False?

17. Porous, unconsolidated clays encourage infiltration better than fractured or jointed bedrock. True or False?

D. Multiple choice:

1) Which of the following statements about stream transport is TRUE? a) A stream’s competence is a measure of the diameter of the largest particle that the stream can transport. b) A stream’s competence is proportionate to the square of its velocity. c) A stream’s capacity is a measure of the maximum quantity of sediment the stream can transport. d) All of the above

2) Which of the following statements concerning a stream’s sediment load is NOT true? (a) The brown color in muddy rivers is caused by an unusually high dissolved load. Note: The dissolved load is colorless. The suspended load is often brown. (b)Large stones that cannot be carried within a stream’s suspended load can sometimes be transported by traction in the stream’s bed load. (c) Fine particles of clay are likely to be transported as part of the suspended load. (d)Both flat and low-density particles tend to remain within the suspended load. 3) The volume of a stream’s dissolved load is dependent on all of the following factors EXCEPT: (a) climate. (b)stream velocity. (c) bedrock composition and acidity of the water. (d)topography.

4) Braided streams with, large amounts of very coarse bed-load sediments, deposit what bedform? (a) Point bars. (b)Mid-channel bars. (c) Levees.

5) Accumulations of gold, platinum, or silver would most likely be found: (a) on the outside of meander curves, where the high velocity of the water has embedded them in the banks. (b)in point bars on the inside of meander curves, and near boulders, where stream velocity is the slowest. (c) distributed evenly throughout the stream bed.

6) Natural levees result when: (a) streams flood their banks and deposit sediment directly on top of the banks. (b)streams erode downward in their channel, leaving their banks higher relative to the surface of the stream. (c) hard, erosion-resistant rocks become part of a stream’s banks. (d)smaller streams flow parallel to a main stream and deposit material on the stream bank.

7) The highest point along a meandering stream floodplain would be: (a) the channel bank. (b)the levees. (c) the channel gravels (d)the point bar deposits. 8) The primary difference between a delta and an alluvial fan is that: (a) alluvial fans are erosional features, whereas deltas are depositional features. (b)alluvial fans result from deposition into inland lakes, while deltas result from deposition into the ocean. (c) alluvial fans form at the source of a stream and deltas form at the mouth of a stream. (d)alluvial fans are formed on low-land plains, while deltas are formed in a standing body of water.

9) Which of the following statements about deltas is NOT true? (a) The material that constitutes a delta is called alluvium. (b)Foreset beds are sediments deposited the farthest from the mouth of the stream. (c) Bottomset beds are sediments deposited in horizontal layers away from the mouth of the stream. (d)Topset beds are sediments deposited in horizontal layers on the surface of the delta near the mouth of the stream.

10) The highest point along a meandering stream floodplain would be: (a) the channel bank. (b)the levees. Identical to # 7 (c) the gravel load (d)the point bar deposits.

11) Which of the following conditions is most favorable for delta formation? (a) Where waves and currents immediately sweep away most of the river’s delivered sediments. (b)Where powerful storm waves carry all of the river’s delivered sediment. (c) Where a large sediment load is delivered to quiet coastal waters. (d)Where a small sediment load is delivered along the river’s short path to quiet coastal waters.

12) A large cone of depression is least likely to develop when: (a) a large amount of water is removed from an aquifer. (b)there is little precipitation in an area. (c) the aquifer has minimum permeability. (d)recharge exceeds discharge. E. Short Answer

1. List and describe the parts of a stream system.

2. How does stream velocity differ in different parts of a stream channel? Fast in steep uplands, slower on plain.

3. Explain porosity and permeability, and define an aquifer. Porosity: space between grains Permeability: ability of water to flow between grains Aquifer: sediment with high permeability, and containing water.