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Simon Fraser University *
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Course
111
Subject
Geography
Date
Dec 6, 2023
Type
Pages
5
Uploaded by MinisterGrasshopperMaster522
SFU-Geography
Lab 9
Geography 111
Name:
Student ID:
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Lab 9 – Response Sheet
Part 1: Drainage Basin Hydrology
1.
The map on the handout is a simplified map of the Fraser River drainage basin. Fill in the stream
order at the location of each box using the Horton-Strahler method.
One is already filled in for
you. Take a photo of your completed map and insert it as an image below. (2)
Part 2: Stream Discharge and related Climate Variables
In November 2021, the Sumas valley in Abbotsford BC (part of the greater Fraser River basin)
experienced catastrophic flooding. One affected river was the Chilliwack River, a tributary of the Fraser
River. The Chilliwack River drainage basin is shown in Figure 1. The floods were a result of a combination
of factors, some of which are shown in the data in Figure 2 from the Chilliwack River, during an intense
rainfall event that occurred from Nov. 13-18, 2021. Figure 3 shows discharge data from the same river in
2019 and the mean (average) discharge data from 1943-2019. Figure 4 shows monthly climate normals
(average values of temperature and precipitation) for Chilliwack. Examine the data in the figures and
answer the questions below.
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/23
SFU-Geography
Lab 9
Geography 111
Figure 1. Chiiliwack River Basin. Source: FVRD, 2010.
2.
According to the mean annual discharge hydrograph (Figure 3), in which months of the year
does the Chilliwack River normally experience spikes in discharge? (1)
3.
Compare your answer in #2 to the precipitation data in the climate normal graph (Figure 4). Do
the months with high discharge seem to correspond with months of high precipitation? If not,
what else might contribute to a spike in discharge? (1)
4.
Based on Figure 2 (a), (b), and (c), make
three
observations related to precipitation, snowmelt,
and temperature in the time period studied. (3)
2
SFU-Geography
Lab 9
Geography 111
5.
Refer now to Figure 2(d). Is the peak river discharge
before
,
during
, or
after
the peak of the
precipitation and snow melt?
Highlight the correct answer. (1)
6.
What was the peak discharge of the Chilliwack River in November 2021? (in m
3
/s) (1)
7.
This discharge measurement is taken at a particular station on the Chilliwack River (at Vedder
Crossing).
a.
The cross-sectional area (A) of the river channel at Vedder Crossing is 144 m
2
. The width
is 48 m. What is the average depth? Show your calculations. (1)
b.
Using the peak discharge from November 2021 (Question #6) and your answer to 7(a),
calculate the average velocity of the Chilliwack River at the time that peak discharge
occurred. (2)
8.
Using Figure 3, what is the average peak discharge for the Chilliwack River in November? (in
m
3
/s). How does the November 2021 discharge compare to the average? (2)
9.
What was the cumulative precipitation (in mm) in Chilliwack during the intense rainfall event in
November 2021?
(1)
10.
What is the average amount of precipitation (in mm) in Chilliwack in November? How does the
cumulative precipitation in the November 2021 rainfall event compare to the average? (2)
11.
What was the peak air temperature in Chilliwack in November 2021? (1)
12.
What is the average air temperature in Chilliwack in November? How does the November 2021
temperature compare to the average? (2)
3
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SFU-Geography
Lab 9
Geography 111
13.
Based on the data you have analyzed here, hypothesize (make an evidence-based guess) about
factors that were related to the catastrophic flooding in this drainage basin in November 2021.
(2)
14.
If you wanted to understand more about the potential causes of the flooding, what other data
might you want to collect? (1)
Figure 2. Hydro-meteorological conditions for the Chilliwack basin showing a) (top) hourly precipitation,
cumulative precipitation, and cumulative melt plus precipitation; b) (second row) hourly
SWE
and melt; c)
(third row) hourly air temperature; and d) (bottom) hourly streamflow. All data are plotted for the period
November 13th, 2021 to November 18th, 2021. Source: Gillett et al., 2022.
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SFU-Geography
Lab 9
Geography 111
Figure 3. Mean Annual Discharge Graph for Chilliwack River at Vedder Crossing (Station 08MH001) [BC].
Source: Wareroffice.gc.ca. Red line shows 2019 data; green line shows mean (average) data from the
period 1943-2019.
Figure 4. Climate normal for Chilliwack (averages of 1980-2010 data). Source: Environment Canada
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