GEOL 1 Lecture Notes - Lecture 23: Longshore Drift, Outer Banks

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21 Sep 2020
Hao Tran
Physical Geology
Notes: Geol 1
Coastal Erosion
Can occur along emergent & submergent coasts
Case Study- Cape Hatteras
The Outer Banks of NC
Strong longshore currents
The Cape Hatteras lighthouse
1868: 1500 ft inland
1998: just 120 ft from the ocean
Q: What was the average rate of erosion in this area form
1869-1998? (Ans: 10ft/yr)
To save the lighthouse, in 1999-2000 it was moved 1900 ft inland
over the course of 23 days (Costs $15 million)
Coastal Erosion cont.
How do we deal with coastal erosion?
1st Approach: Zoning
Build farther inland
Setback Distance
How far to move inland
Erosion lines
Line along the coast marking where erosion will
move the shoreline to in the future.
Ex. The E-10 line shows you where the shoreline
will be in 10 years from now given the current rate
of erosion
Erosion rate x Interval = E-line distance
Ex: you want t know where the coastline will be in
10 years
Given: erosion rate = 10 ft/yr
10 ft/yr * 10 yrs = 100 ft father inland
How far inland should the setback distance be in
order to keep buildings safe?
National: E-60
SC: E-40
Why doesn’t SC use the national E-60 line?
Tourism (#1 revenue)
2010: tourism generated $18 billion for SC
2nd Approach: Barriers
Protect the shore in one of two ways:
Weaken waves
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