1.Which soil is probably a dense, heavy clay?These questions should give you an idea of the kind of thinking I am after, and the way the questions may be structured. Answers to the questions, along with the reasoning, are given at the bottom of this page. I suggest that you try to take this exam without looking at the answers -- then check and see how you've done. When you miss a question, use my explanations to help figure out where you went wrong.
Questions 1-6 refer to the diagram below
a. 1 b. 2 c. 3 d. 4 e. there is no way to tell
2. Which soil is probably a gravel or coarse sand?
a. 1 b. 2 c. 3 d. 4 e. there is no way to tell
3. One of these soils is in a heavy forest. Which one is the most likely candidate?
a. 1 b. 2 c. 3 d. 4 e. there is no way to tell
4. One of these soils is rich in swelling clay (montmorillonite). When dry, this soil shrinks greatly and many cracks open up. As it gets wet, the clays swell and the cracks close. Which graph represents this soil?
a. 1 b. 2 c. 3 d. 4 e. there is no way to tell
5. Which soil would be best if you were looking for a site for a septic tank drain field?
a. 1 b. 2 c. 3 d. 4 e. all would be equally good
6. On which soil would overland flow be most readily generated?
a. 1 b. 2 c. 3 d. 4 e. all would generate equally readily
7. In a gently-sloping, grassy, humid&endash;area drainage basin, most of the water appearing as streamflow during storms gets to the stream by:
a. direct overland flow (Horton overland flow) contributed from nearly the whole basin area b. overland flow from saturated areas close to the stream channel (saturation overland flow) c. water moving downslope to the stream through the unsaturated zone of the soil (subsurface stormflow) d. increased groundwater discharge into the stream e. rain falling directly into the stream
8. The average annual rainfall over a forested drainage basin is 70 inches. Evapotranspiration by plants averages 35 inches per year. About 10 inches of water per year percolates down to the water table and becomes groundwater. What is the average annual surface runoff (streamflow) for this drainage basin?
a. 10 inches b. 25 inches c. 40 inches d. 60 inches e. 70 inches
9. As a heavily cut-over (logged) area becomes reforested, what do you expect would happen to the average discharge of streams draining the area?
a. it would probably increase, chiefly because more water would infiltrate b. it would probably increase, chiefly because less water would evaporate from the soil c. it would probably decrease, chiefly because there would be less overland flow d. it would probably decrease, chiefly because more water would be lost by evapotranspiration e. there would probably be no change in streamflow
10. If a flood of a particular size has a recurrence interval of ten years (i.e., it's the "ten-year
flood"), which of the following statements about it are true? (Mark T or F, then choose answer)
___in the next 100 years we will have exactly ten floods of that size or larger
___a flood of that size or larger will occur every ten years
___after a flood of that size occurs, we will have to wait at least ten years before one
that size or larger occurs again
___on the average, ten floods that size or larger will occur in any 100-year period
___a flood of that size (or larger) has one chance in 10 (i.e. a probability of 1/10) of occurring
in any given year
The correct matching order is:
a. TTTFF b. FFFTT c. TTTTT d. TTTTF e. FFFFT
11. If a river has a braided pattern, which of the following statements about it are likely to be
true? (Mark statements T or F, then choose answer)
___the channel is likely to be relatively stable (i.e. changes position relatively slowly)
___the stream has very easily erodible banks
___the stream is carrying a heavy and very coarse sediment load
___the channel bed has a relatively steep slope
___the stream carries most of its load in suspension
The correct matching order is:
a. TFFFT b. FFFFF c. FTTTF d. TTTTT e. TFTFT
12. How does an earthflow differ from a debris flow?
a. earthflows are slower moving than debris flows b. earthflows involve less water and are more 'viscous' than debris flows c. earthflows have a more hummocky, lobate appearance than debris flows d. earthflows are less likely to cause catastrophic loss of life than debris flows e. all of the above answers (a&endash;d) are correct
13. Colluvium is material which has been moved downslope by mass-movement processes such as creep,
rainsplash, sheetwash, and landsliding. Which of the following statements about colluvial
deposits are likely to be true? (Indicate T or F before each choice, then choose answer.)
Colluvial deposits are:
___typically full of angular particles
___usually well-sorted
___commonly very uniform in thickness
___generally unstratified or very poorly stratified
___rarely indicators of future slope instability
The proper matching order is: a. TFFTF b. TFTFT c. FTFTF d. FTTFT e. TFTTF
14. If you wanted to stabilize a large landslide, which of the things listed below would
probably be most effective?
a.loading the top of the slope to increase friction b.steepening the slope so that the water runs off faster c.cutting down trees on the landslide to remove their weight from the slope d.installing drains to drain water out of the rock and thus reduce pore pressures e.none of the above will be effective&endash; all will increase the chance of landsliding
15. A river flows into the sea and forms a delta. If the area is tectonically stable (no uplift
or downwarping), the position of the delta shoreline depends chiefly upon:
a. the total amount of sediment brought down by the river b. the depth of the sea there c. the strength of the waves d. the relative rates of deposition by the river and erosion by the sea e. the local rate of sea&endash;floor spreading
16. Mount Olympus on the Olympic Peninsula of Washington is glaciated while many higher peaks in
the Rocky Mountains at the same latitude are not because Mt.Olympus:
a.is steeper b.has bigger south-facing slopes c.is in an area of much higher precipitation d.is colder e.once had continental glaciers butting up against it and these left pieces of themselves behind
17. Which of the following landforms is not the result of glacial erosion?
a. cirques b. fjords c. U-shaped valleys d. drumlins e. hanging valleys
18. Of the features listed below, which can be associated with both continental (ice sheet) and
valley (mountain) glaciation? (Circle correct features as you go, then pick answer.)
1) cirques 2) eskers 3) highly scoured bedrock 4) erratics 5) drumlins 6) tall, very steep-sided morainal ridges 7) grooves and striations a. 1 and 6 b. 2 and 5 c. 3, 4, and 7 d. none of the above indicate continental glaciation; all indicate valley glaciation e. all of the features are highly indicative of continental glaciation
Answers (with reasoning):
To answer questions 1-6 you must be able to interpret the graph. It shows how the total amount
of water infiltrated into the soil varies with time after the beginning of rain.
1. d (Line 4 represents a soil that infiltrates very little water. After 140 minutes only about
2 inches have been infiltrated. Clays have low infiltration capacities.)
2. a (Line 1 represents a soil that has a high infiltration rate at the beginning, and whose
infiltration rate stays nearly constant -- and high-- with time. Gravels and coarse
sands have high infiltration rates.)
3. a (Heavy vegetation -- especially forest-- protects the soil from sealing by raindrop
impact and keeps infiltration rates high. Line 1 starts off high, and since its slope
is nearly constant, it shows that the infiltration rate is changing very little with
time, suggesting good protection.)
4. c (Line 3 starts out high, and then quickly flattens off showing that relatively little
more water is being infiltrated. This is what you'd expect if a clay soil had open
cracks in it--which would admit water easily-- at the beginning, and then the cracks
closed up as the clays swelled.)
5. a (For a septic-tank drain field you need a material that passes water easily -- preferably
a sand or gravel. See answer to question 1 for reasoning.)
6. d (The soil represented by line 4 has the lowest infiltration rate at all times.)
7 b (Gently sloping meadowy areas commonly have high water tables, so the soils saturate
quickly and then generate saturation overland flow because the rain cannot easily
enter the saturated soil.)
8. b (Runoff = rainfall - evapotranspiration loss - groundwater outflow: 70-35-10 = 25)
9. d (As the forest regenerates, more water will be lost through evapotranspiration, thus
reducing the streamflow.)
10. b (Recurrence interval is a statistical concept. Answer stems directly from its definition.)
11. c (Braided streams tend to have easily erodible banks and carry a large amounts of mostly
coarse sediment, which moves by bouncing and rolling dowen the bed, i.e., as bedload.
The channels are wide and shallow, with steeper longitudinal gradients.)
12. e (Refer to basic descriptions of earthflow and debris flow.)
13. a (Mass movements cannot readily sort or round particles, and because the material is
just dumped, stratification tends to be poor or nonexistent, and thickness can be
quite irregular.)
14. d (Draining water reduces pore pressure and increases stability by increasing the
frictional strength of the earth materials. All the other suggestions will
decrease slope stability.)
15. d (If the coastline is tectonically stable, then delivering more sediment to the delta
will cause it to grow seaward, while erosion by the waves will cause the shoreline
to retreat landward. Thus the position depends on the balance between the two.)
16. c (Glaciers will form wherever the winter accummulation of ice and snow exceeds the
amount lost by melting and evaporation in the summer. Because the Olympics get
a huge amount of snowfall -- think of the Olympic rainforests at lower elevations--
they have developed glaciers.)
17. d (Drumlins are formed by continental glacier deposition, not erosion.)
18. c (Cirques and steep-sided morainal ridges are associated only with valley glaciers;
eskers and drumlins are associted with continental glaciers. Both kinds of glaciers
can scour and groove bedrock.)