Coastal Hazards - Investigations in Environmental Geology - page 190

190 II. Introduction to Geologic Hazards

FIGURE 11.15 (a) Coastal change of Isles Dernieres, Lousiana, between 1887 and December 9, 1996, showing land loss and breakup
of the island; (b) Aerial photographic mosaic, 1996.
(Adapted from Penland et al., 2003, http://pubs.usgs.gov/of/2003/of03-398/posters/pdf/cont_pdf/id_atlas.pdf )

7. a. In 1935, what was the maximum length of this island in
feet (not including small eastern islands)? (Use a paper edge to
measure the map distance and compare with the map scale.)

published in 1935. Note the dashed lines in the 1935 quad-
rangle that could form a set of equal squares if extended.
Each square on the map is numbered and is known as a sec-
tion. With this set of numbered sections (squares) we have a
very good reference system that we can use to trace the
changes in this barrier island. Also on this map are named
bench marks.

b. In 1935, what was the maximum width?

c. In 1994, what was the maximum length of this island in
feet (not including small eastern islands)? 6. a. In the 1935 map (Figure 11.16), what is the section num-

ber that contains the word ISLES?

d. In 1994, what was the maximum width?

b. What sections contain the word DERNIERES?

8. a. Measured along the boundary between Sections 33 and
32, how many feet has the Gulf side of the island retreated
between 1935 and 1994?

c. What is the name of the triangulation point on the west
end of the island?

b. What is the average rate of retreat? (Show your work.)

d. What is a section?

9. a. What part of the bayside (N side) of the island showed
the most change between 1935 and 1994? (Indicate by Sec-
tion number and mark on Figure 11.16.)

e. What is the area of a section? (See the map exercise of
this manual.)

f. Write out the abbreviations for T 23 S and R 15 E. (Hint:
See the map exercise of this manual.)