GEOL 1 Lecture Notes - Lecture 23: Longshore Drift, Outer Banks
0 views2 pages
Hao Tran
htran170@ivc.edu
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
■ Formula
● 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