can you help with the questions attached?

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GEOG 102 Week 8 Lab 1

GEOG 102 Week 8 Lab:

Risky Waters: Determining Flood Risk

Overview
All streams generate an average annual flow, but over time, most streams exhibit a wide
variation in streamflow from very low stages to large floods. On September 12, 2013, heavy
precipitation in Rocky Mountain National Park sent floodwaters roaring down the Big
Thompson River and its tributaries (Figure 1). The epic flooding damaged or destroyed the
major roadways along with hundreds of homes and businesses in this narrow canyon (Figure 2).

Figure 1 Big Thompson Rover- Little Thompson River watershed in relation to cities and
highways

Steep slopes and sparse vegetation combined with heavy rain have lead to repeated flooding in
the Big Thompson River canyon and communities downstream: A flash flood in 1976 killed 144.
In 2013, 8 died as floods caused $2 billion in property damage. The average number of years
between floods of a certain size is the recurrence interval. These intervals are based on the

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GEOG 102 Week 8 Lab 2

magnitude of the annual peak flow, which occurs once a year. However, the actual number of
years between floods of any given size varies because of highly variable weather patterns, plus
human impacts such as deforestation, urbanization, dam building, and the planting of crops can
affect runoff. The goal of this lab is to understand the concept of a stream flood recurrence
interval.

Watch the prelab video at https://mediaplayer.pearsoncmg.com/assets/secs-christopherson-
gc1-prelab-10

Figure 2: Deadly topography

Application
As a watershed manager working for a county at the base of the Rocky Mountains, you are
charged with calculating a flood recurrence interval, so that county residents who live near
streams have some understanding of the potential frequency of large flood events.

https://mediaplayer.pearsoncmg.com/assets/secs-christopherson-gc1-prelab-10

https://mediaplayer.pearsoncmg.com/assets/secs-christopherson-gc1-prelab-10

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Inc.

GEOG 102 Week 8 Lab 3

Objectives
• Outline a drainage basin.

• Calculate a recurrence interval using actual stream data.

• Apply these data to predict flood risk.

Grading
Grading for the lab will be as follows: Remember the point score for the questions shows how
many sentences or elements should be included in the answer. As always, answers will be
graded on accuracy, completeness, spelling and grammar. As always, make sure your
sentences are complete and your paragraphs are well organized.

✓ Part A – Written component 35 pts
✓ Part B – MyLab and Mastering component 10 pts
✓ Neatness, spelling and grammar 5 pts

Note on Academic Honesty: The written and online components for this week’s lab are to be
done on your own. Working together with classmates is acceptable and encouraged, but the
work you turn in must be your own words. Refer to the course syllabus and the OSU General
Catalog for the university policies concerning academic dishonesty.

At the end of your lab, you must type or write the following words “This work, including the on-
line component is entirely my own. I did not copy the whole or any part of my answers to this
this lab from anyone else, from a web site, from a book, or from any other source.” Underneath
these words, type or sign your name and date.

Part A

Draw and Calculate the following:

1. Your first exercise is to outline, with a colored pen or pencil, the drainage basin for the Big

Thompson River (Figure 3, page 6). Note that in a few places (red marker), some of this has
been done for you (2 pts).

Next, mark the following: (8 pts)

a. headwaters
b. interfluve
c. mouth, or location where the river flows onto the Great Plains

2. The next step is to calculate the flood recurrence intervals and rank flood events by their

maximum discharge and their recurrence intervals. From this data, it is possible to calculate
the probability of the flood recurring. Table 1 (page 7) lists nine years of maximum daily
streamflow stage (cfs) for the Big Thompson River. (6 pts)

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GEOG 102 Week 8 Lab 4

a. In the third column, rank this data by year from the largest amount (rank of 1) to the
smallest (rank of 9).

b. In the fourth column, calculate the probability, in percent, of the flood recurring
using the formula:

rank/( n + 1 ) × 100 ; where n = the number of years with available data

c. In column five, rank the recurrence intervals. This is determined by the following
equation:

RI = (N + 1)/M

Where: RI = the recurrence interval
N is the number of years the floods are on record
M is the rank of the flooding event (largest flood M = 1)

Because there are nine years of data, this calculation becomes 9 + 1, divided by the
rank number you assigned

Analyze and Conclude

3. In your completed data table, how is the recurrence interval related to the rank and

probability of each year’s maximum discharge? (3 pts)

4. Based on your answer to question 3, what maximum discharge might residents along the
Big Thompson River typically expect? Explain. (3 pts)

5. Does knowing the recurrence interval enable you to predict floods on the Big Thompson
River during the next nine-year period? Explain why or why not. (3 pts)

6. In many areas of the world, accurate stream recurrence interval data now extend over one
century. After a record (rank 1 flood) in these areas, the media often refer to it as a “once in
a century flood,” or a “100-year flood.” In your job as a watershed manager, does this mean
that prospective home and business owners are safe from another event of that magnitude
for more than the average human lifetime? Explain. (3 pts)

7. Looking at Figure 3 on the page 6, describe the difference in flow characteristics discussed
in Section 10.5 (in your text) for stream water flowing in the middle of the canyon and the
same water as it flows out of the mountains and across the Great Plains just below the
Rocky Mountains. (3 pts)

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GEOG 102 Week 8 Lab 5

8. Hypothesize how and why the following landscape changes might influence future floods in
the lower sections of the Big Thompson River watershed: (3 pts)
a. More urbanization
b. A large forest fire
c. A series of upstream dams

Part B

Part B of this lab is online and continues to the impact of rivers on the landscape. Log in to
Canvas to complete the online portion of this lab in the MyLab Mastering section.

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GEOG 102 Week 7 Lab 6

Figure 3 Digital relief map of the Big Thompson watershed (NOAA)

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GEOG 102 Week 7 Lab 7

Table 1 Data for calculating flood recurrence interval