Environmental Geology Lab: Flooding Part 2
NAME:________________________________
Part 1: Introduction to Topographic Maps and Contouring
Chapter 9 in your manual will help with the following questions:
1. Contour lines represent points of equal_________________________________.
2. On p.216 in your lab manual you will see two maps of Hawaii, both contoured. What
is the difference between the maps?
3. What does a contour interval tell you?
4. What is an index contour?
5. What does it mean when contour lines are very close together?
6. On the map of a hill, below, the index contours of 100’ and 200’ are marked. Draw in
the 4 additional contour lines you would see on a topographic map if this map has a
25’ contour interval.
100’
200’
7. Now you are going to contour Figure 1 (on the next page) using a 2ft contour
interval.
a. To create a topographic map:
i. Locate the lowest and highest elevations on the map. This will help
you determine the elevation of your first and last contour lines.
ii. Draw your contour lines to separate points of different elevation. For
example, any points greater than 2ft but less than 4 ft in elevation
should fall between the 2 ft and 4ft contour lines.
iii. It is ok for lines to extend off the map.
iv. Remember that contour lines never cross.
1
Examine your topographic map and answer the following:
8. What location has the highest elevation (Ex. NE, S, etc.)?
9. Which general location on the map would you expect to flood first?
10. Create a topographic profile of Bull Street using the map you just contoured, on the
graph paper at the end of the lab. You should have distance on the x-axis and
elevation on the y-axis. For distance use the scale of 1inch=250’ (you will need a
ruler!).
11. According to your profile, where is Calhoun most likely to flood?
Figure 1
2
Part 2: How Does Flooding Occur?
A. Extreme high tide flooding, Sea Level Rise
This site discusses “nuisance flooding,” or flooding that occurs without a storm event. It
causes frequent road closures and compromises infrastructure.
Scroll down to the table at the bottom of this site and answer the following questions.
http://www.noaanews.noaa.gov/stories2014/20140728_nuisanceflooding.html
1. Where does Charleston rank for “Nuisance Flooding?”
2. How many meters above the mean higher high water mark is considered nuisance
flooding?
3. 1 meter=3.28 feet. Convert your above answer to feet:
4. In 1963, how many days per year on average did nuisance flooding occur?
5. In 2013, how many days per year on average did nuisance flooding occur?
6. What percentage increase is that?
7. Why do you think nuisance flooding is increasing?
So how does this “nuisance flooding” occur? Use this site to explore extreme high tides
(often called ”King Tides”): https://coast.noaa.gov/tidalfloodingvis/?redirect=301ocm
8. On the left hand bar, click on “Formation of Extreme High Tides” and answer the
following:
a. How does an extreme high tide occur?
9. On the left hand bar, click on “Impacts of Extreme High Tides” and answer the
following:
a. Carefully watch the mean high tide line. How does flooding occur during
these extreme high tides?
b. What could make the flooding from extreme high tides worse?
c. What are some results that affect the community from these high tides?
10. On the left hand bar, click on “Flooding and Sea Level Rise” and answer the
following:
a. According to tide gauges, how much have sea-levels risen in the past 100
years (give the range)?
b. What does this mean for tidal flooding in coastal communities?
3
Use this site to answer the following questions:
https://tidesandcurrents.noaa.gov/waterlevels.html?id=8665530&units=metric&bdate=19
500128&edate=20150928&timezone=GMT&datum=MSL&interval=m&action
11. Below the graph:
a. Select “plotting monthly means as” MSL, which is mean sea level.
b. Set the date range from Jan 1, 1950 through Sept 1, 2016.
c. Make sure the “Datum” dropdown menu is also in MSL
d. Click Plot (on the right, in blue).
12. If you move your cursor along the graph, sea level data for Charleston, SC
throughout this time range are visible. What is the datum for Jan.1, 1950?
13. What is the datum for Aug.1, 2016?
14. What is the difference in MSL for Charleston for this time frame?
15. What is the highest MSL datum on this graph?
16. When did it occur (we will explore this event later in lab)?
On this site: https://coast.noaa.gov/slr/
 Click on the Flooding Frequency button on the upper left
 Use the dropdown menu on the upper right to zoom into SC, and the +/- to
zoom further into Charleston
 Click on the tide gauge icon next to the Charleston peninsula
17. How many coastal flooding events do we currently experience per year in
Charleston?
18. How many events can be expected with a 1m rise in sea level?
19. Areas in red indicate shallow coastal flooding areas. Which areas on the peninsula
are most vulnerable?
20. From what you learned about the history of the peninsula during the earthquake
lab, and from the historic maps posted on OAKS, why do you think these areas flood
most often?
B. Storm flooding
Use this site to answer the following questions:
http://www.stormsurge.noaa.gov/overview.html
21. What is a storm surge?
22. What causes a storm surge?
4
23. If the weather service issues a storm surge warning of 15 feet, what does that mean
for the area in which the warning is issued?
24. The depth of flooding is generally less the further inland you go. Where would the
exception to this be?
25. Click on the “Causes of Coastal Flooding” tab along the top of the website. What two
things can cause a storm surge to create even greater flooding? (Read bullets 3&4)
a. ________________________________________________________________________________________
b. ________________________________________________________________________________________
26. Click back to the “Storm Surge” tab at the top of the site. Over what type of water
does a tropical storm form?
27. Do you therefore think that rising sea surface temperatures could cause more, or
more intense, tropical storms?
Click through the arrows on the slideshow on this site and answer the following questions:
https://www.edf.org/climate/climate-change-and-extreme-weather
28. How do weather events intensify with hotter air?
29. What have the storms in recent years confirmed (that the models predicted)?
Part 3: Case Studies
A. Charleston, SC: Oct 1-5, 2015 Flooding
Use this article to answer the following questions:
http://www.weather.gov/chs/HistoricFlooding-Oct2015
1. What was the cause of this flooding event (was there a storm, was it tidal
flooding…etc.)?
2. On the left-hand bar of this site, scroll down to the “Storm Total Rainfall” heading.
There were isolated maximum amounts of rainfall in Charleston in excess of how
many inches?
3. Convert this to feet:
4. Scroll down further on the page to “Flood Damage and Impacts.” What was the
damage from this event?
5. Using the NOAA site from earlier, we will now zoom in on this event. Go to:
https://tidesandcurrents.noaa.gov/waterlevels.html?id=8665530&units=standard
&bdate=20151001&edate=20151006&timezone=LST&datum=MSL&interval=6&act
ion=
a. Be sure that the options selected are: Units=feet; Datum=MSL; and Dates are
Oct.1-5, 2015.
5
b. What is the highest datum for this event and when did it occur?
6. On the map you contoured in Part 1, draw a contour line representing this event,
using the elevation in 5b, above. Label this contour line 2015 SS (for Storm Surge.)
B. Charleston, SC: Oct 27, 2015 Flooding
Use this article to answer the following questions:
https://www.washingtonpost.com/news/capital-weather-gang/wp/2015/10/27/historichigh-tides-from-supermoon-and-sea-level-rise-flood-the-southeast-coast/
7. What was the cause of this flooding event (was there a storm, was it tidal
flooding…etc.)?
8. What was the peak of this high tide, in feet?
9. What was the predicted level?
10. What was the peak level of the tide from the same event in Savannah, GA?
11. What factors lead to the inundation of flood waters?
12. Using the NOAA site from earlier, we will now zoom in on this event. Go to:
https://tidesandcurrents.noaa.gov/waterlevels.html?id=8665530&units=standard
&bdate=20151024&edate=20151030&timezone=LST&datum=MSL&interval=6&act
ion=
a. Be sure that the options selected are: Units=feet; Datum=MSL; and Dates are
Oct.24-30, 2015.
b. What is the highest datum for this event and when did it occur?
13. On the map you contoured for Part 1, draw a contour line representing this event,
using the elevation in 12b, above. Label this contour line 2015 TF (for Tidal
Flooding.)
C. Charleston, SC: Sept. 22-22, 1989 Hurricane Hugo
Use to this site to answer the following questions:
http://www.weather.gov/chs/HurricaneHugo-Sep1989
14. Where did this hurricane make landfall?
15. What was its category when it hit land?
16. What was the estimated cost of damage from this hurricane?
6
17. How many deaths were there as the result of Hugo?
18. Scroll down on the page until you see the section of maps. Click on the top left map,
which is a visualization of the storm surge if Hugo had made landfall just 20 miles S
of where it did.
a. What would the highest storm surge depth have been in this scenario?
19. Scroll down to the map titled “Storm Tides” and click on it.
a. What was the highest storm surge from Hugo?
b. Where did it occur?
c. What was the storm surge in downtown Charleston from Hugo?
d. On the map you contoured for Part 1, draw a contour line representing this
event, using the elevation above. Label it 1989 HH (for Hurricane Hugo).
e. How much of your map would be flooded in another event like Hugo?
20. List the three events (both type of event and the year) in order from greatest to least
storm surge levels:
a. Type and Year: _________________________________________ Storm Surge (ft): ________
b. Type and Year: _________________________________________ Storm Surge (ft): ________
c. Type and Year: _________________________________________ Storm Surge (ft): ________
21. As you can see, hurricanes and tropical storms are not the only threat to Charleston
when it comes to flooding. Go to this site:
http://www.scdhec.gov/HomeAndEnvironment/Water/CoastalManagement/KingT
idesHelp/
a. When is the next predicted King tide?
b. Note that on this site you can upload pictures of flooding from King Tides,
and help DHEC better understand coastal vulnerability. It’s an even bigger
help if you can snap a shot of the same location at peak low tide for
comparison!
7