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Assignment Chapter 16: Streams, Flooding

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Physical Geology, GLY-1010
Student Name ___________________________
Assignment Chapter 16: Streams, Flooding
Complete the following assignment and submit on the day of your Exam #4. Activities based on the
materials by Prof. Katryn Wiese (City College of San Francisco).
1. Describe the distribution of Earth’s water. What percentage is fresh? Of that, what percentage is
in each of glaciers, groundwater, and lakes + streams?
2. What is the base level? What/where is ultimate base level for most streams? What natural or
artificial features can become local base levels?
3. A stream starts 2000 m above sea level and travels 250 km to the ocean. What is its average
gradient in m/km? This stream develops extensive meanders lengthening its course to 500 km.
Calculate its new gradient. Which steepness represents the more youthful stream? Why? (Be
sure in your explanation that you understand the meaning of the headwaters and the mouth of
a stream.)
4. Under what conditions will a stream erode (rather than deposit) sediment? Where along a river
does this most occur?
5. Through what methods do streams physically and chemically weather rock?
6. Describe how the shapes of river-eroded and glacially eroded mountain valleys differ (be
Chacapoyas, Peruvian Amazonian region
Ruco, Ecuatorian Andes, picture by J. Zapata
7. List and describe the three kinds of load that a river transports. Include pictures from internet.
8. Under what three conditions will a stream deposit (rather than erode) sediment?
9. Identify the following features on the pictures and specify if they are present on high, medium
or low gradient areas: rapids, meanders, point bar, cutbank, waterfall, V-shaped valleys,
mountain lake, braided river, longitudinal bars, delta, delta plain, river mouth, estuary, oxbow
lake, meander scars, floodplain, levees.
10. What main characteristic of a region makes a stream running through it braided?
11. What main characteristic of a region makes a stream running through it meander?
12. On the picture below, label the areas of erosion (cut banks) and accumulation of sediment
(point bars); show with arrow the direction of migration of the current meanders and identify
which meander will be abandoned first.
13. Sketch a transversal section across a meandering river indicating the location of the point bar
and the cut bank.
14. Considering the path of an stream form headwaters to mouth:
Where is EROSION RATE highest? (circle) Headwaters / Mouth
Where is FRICTION / DRAG highest? (circle) Headwaters / Mouth
Where is GRADIENT highest? (circle) Headwaters / Mouth
Where is DISCHARGE highest? (circle) Headwaters / Mouth
Where is WATER VELOCITY highest? (circle) Headwaters / Mouth
Where is transported sediment coarser? (circle) Headwaters / Mouth
15. Label the channel, levees and floodplain on the picture below.
16. Explain what happens during a flooding event. What is a flashflood? Sketch a hydrograph
comparing a flashflood and a slow flooding event.
17. How are the levees and floodplain formed? Sketch and explain. What type of sediment makes
up the levees? What type of sediment makes up the floodplain?
18. What are the 10 years, 100 years, and 500 years floodplain? When is higher the risk of flooding?
19. The following features are the product of increasing stream gradient during tectonic uplifting.
What is the name of this feature? Why is so flat? Number the features from oldest to youngest,
using 1 for the oldest.

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