94) ________ streams are not connected to groundwater systems and only flow after
precipitation events.
A) Perennial
B) Intermittent
C) Ephemeral
D) Temporary
95) ________ streams have some groundwater input, but only flow for certain periods during a
year.
A) Perennial
B) Intermittent
C) Ephemeral
D) Temporary
96)
This graph, showing the effects of urbanization on streamflow over time, is an example of a
A) water budget.
B) hydrograph.
C) climograph.
D) hydrological cycle.
97) Which of the following is incorrectly matched?
A) abrasion — a hydraulic squeeze-and-release action
B) competence — a stream’s ability to move particles of a specific size
C) capacity — the total possible load that a stream can transport
D) fine particles physically held aloft in a stream — suspended load
E) particles rolled and bounced along a stream bed — saltation
98) The process whereby streams deepen their channel is known as
A) headwater erosion.
B) channel incision.
C) stream piracy.
D) saltation.
99) The process whereby streams lengthen their channels upstream is called
A) headwater erosion.
B) channel incision.
C) stream piracy.
D) saltation.
100) The total possible load a stream can transport is its ________, whereas a stream’s ability to
move particles of specific size is its ________.
A) capacity; competence
B) competence; capacity
C) discharge; competence
D) bed load; sediment load
101) The construction of a dam across a river is likely to cause ________ upstream and
________ downstream.
A) erosion; aggradation
B) erosion; erosion
C) aggradation; erosion
D) aggradation; aggradation
102) Which of the following tends to occur when an area experiences tectonic uplift in its
headwater region?
A) The stream will begin to deposit more of its load.
B) The channel will begin to erode downward at a faster rate.
C) The stream will lose energy.
D) The amount of turbulence will decrease.
103) The statistical rating of flood discharge is based on
A) historical records of discharge during precipitation events.
B) floodplain width.
C) average channel depth.
D) the rate of aggradation or degradation of a stream.
104) If you live in an area that was flooded by the 100-year flood last year, you can conclude that
A) the next 100-year flood will occur in exactly 100 years.
B) the next 100-year flood will occur in exactly 99 years.
C) there is a 1% chance you could be flooded by the 100-year flood again this year.
D) you do not have to worry about another flood of that size during your lifetime.
105) A 50-year flood has an annual exceedance probability of
A) 0.5%.
B) 5%.
C) 25%.
D) 50%.
106) Which of the following best describes the relationship of deforestation to sediment load?
A) Trees provide dissolved sediments to the stream; as trees are removed, the dissolved loads are
diminished.
B) Trees roots help “anchor” soil; as the trees are removed, the soil more readily erodes into the
river channels.
C) Forestry waste is often dumped in streams, contributing to the suspended loads.
D) The loss of trees along banks of streams increases stream velocity.
15.2 True/False Questions
1) Rivers have played a relatively minor role in the geography of human history.
2) Because rivers constitute such a small percentage of Earth’s total water supply, they play a
small role in landform change.
3) The meaning of the terms “river” and “stream” sometimes overlap although, in general, the
term “river” is reserved for channels of water larger than a stream.
4) Only larger rivers and streams have their own drainage basins.
5) Drainage basins are closed systems in terms of matter.
6) Drainage basins may cross into multiple countries, compounding the difficulties in proper
watershed management.
7) Stream drainage always eventually reaches the ocean.
8) Variations in rock resistance, climate, and hydrology can influence drainage patterns.
9) A drainage basin is defined by ridges that form drainage divides.
10) Drainage divides control into which basin surface runoff drains.
11) Base level refers to the average stream depth immediately following a normal precipitation
event.
12) The ultimate base level is sea level.
13) In most rivers in humid regions, discharge increases downstream.
14) A perennial stream can go months and even years between flow events.
15) Peak flows refers to the highest discharge that occurs during a precipitation event.
16) Stream velocity is often measured for different subsections of a stream cross section using a
moveable current meter.
17) The suspended load of a stream is the coarser materials that are dragged along the stream
bed.
18) Physical weathering is the main process that contributes to the dissolved load of streams.
19) Erosion is a degrading process whereas deposition is an aggradating process.
20) A braided stream is indicative of excess sedimentation.
21) The higher the sinuosity, the straighter the stream channel.
22) Erosion of the walls of a channel normally occurs on the outside curve of a meander.
23) In a straight channel, the greatest flow velocities are found along the bottom in the middle of
the stream.
24) An oxbow lake is a former meander that has become isolated from the rest of the river.
25) A graded stream is one that has achieved a dynamic equilibrium between degradation and
aggradation.
26) Nickpoints migrate downstream.
27) Floodplain formation occurs while a stream is downcutting rapidly.
28) A floodplain is composed of alluvium.
29) Yazoo streams are blocked from joining the main river in a flood plain due to the presence of
natural levees.
30) An alluvial terrace is evidence of aggradation.
31) Terraces form when a river’s energy increases.
32) Alluvial fans are produced when flowing water loses velocity as it leaves a constricted
canyon and thereby deposits a large amount of sediment.
33) The mouth of a river is where the river reaches a base level.
34) Flood control often produces conditions of worse flooding in subsequent high-water events.
35) A flood recurrence interval of 100 years means that floods of that size will occur only once
every 100 years.
36) A 10-year flood has an annual exceedance probability of 10%.
37) The construction of levees can actually increase the risk of a catastrophic flood.
38) Deforestation in the headwater regions of a river can cause the river to flood more frequently
in downstream areas.
15.3 Essay Questions
1) Define the following terms: drainage basis, drainage divide, interfluve, and valley.
2) Describe five common drainage patterns and the conditions that typically form them.
3) Give the equation for stream discharge. What happens to stream velocity if discharge and
depth remain the same, but width increases?
4) Describe the various ways in which streams can transport material.
5) Describe the common stream channel patterns.
6) Describe or draw and label the stages of development of an oxbow lake, from meander bend
to cut off to oxbow lake, including the location of cut banks and point bars.
7) Discuss the concept of the graded stream. Do most streams approximate a graded stream?
Why or why not?
8) Describe the formation and typical characteristics of a floodplain.
9) Describe the formation of alluvial fans and bajadas.
10) Describe the formation of deltas.