• FitzGerald, Duncan M., and Levin, Douglas, 1981
• FitzGerald at others 1981
• Pilkey, Orrin H., Jr. and Dixon, Katharine L., 1996
• Pilkey, Orrin H., and Neal, William J., 1976
• Pilkey and others, 1989

Required Reading

• Gunnar Hansen, 1993, Island at the Edge of Time
• Dean, Cornelia, 1998, Against the Tide

Coastal Hazards

Natural

• Erosion caused by
  • Hurricanes and storm surges
  • rising sea level
  • Reduction in sediment supply
  • Subsidence (e.g. compaction of deltaic sediments)
• Inlet formation, migration and erosion
• Dune migration
• Overwash
• Saltwater intrusion

• Accelerated foreshore erosion resulting from:
  • dredging of tidal deltas: creates a sediment sink thereby reducing sediment bypassing
  • coastal engineering
    • building or altering structures shift the system out of equilibrium forming regions of concentrated erosion
    • hard stabilization vs. soft stabilizations: pros and cons
      •  "New Jerseyization" of a shoreline: Overwhelming use of hard stabilization: construction of jetties, groins, seawalls etc.
        • seawalls and revetments accelerates removal of beach sand insures that waves reaching the shore are larger
        • groins and jetties and breakwaters: accelerated erosion down-drift
        • Jetties may also force sand offshore
        • beach replenishment: Where is the sand coming from? What are the consequences?
          • old tidal delta?
          • dune?
          • offshore?
    • dune removal or creation: What works from one system may not work for another
  • damming rivers: cuts off sediment supply
  • dewatering of coastal aquifer and/or extraction of oil and gas from coastal regions: causes subsidence
  • channel dredging of inlets (e.g.. Oregon Inlet): creates a sediment sink
•  Bayside erosion can result from
  • dredging (i.e. Wrightsville Beach) and the formation of finger canals
  • attempts to stabilize the shore, which reduces the transport of sand to the bay
• Pollution
  • finger canals increase salinity of local ground water and a .ct as collection sumps for sewage
  • houses built on filled marshland cannot properly dispose of sewage
  • over-pumping aquifers causes saltwater intrusion
•  Overwash resulting from the destruction of dunes caused by
  • breaching for the building of roads, utilities, houses, etc.
  • dune buggies and beach trails
  • change in vegetation (i.e. trees to grass) 

Truths of the shoreline and solutions

(From Pilkey Jr. and Pilkey Sr,1978)

Truths

1. There is no erosion problem until a structure is built on a shoreline
2. Construction by man on the shore causes shoreline changes
3. Shoreline engineering protects the interest of very few often at very high cost in federal and state dollars
4. Shoreline engineering destroys the beach it was intended to save
5. The cost of saving beach property through shoreline engineering is usually greater than the value of the property
6. Once you begin shoreline engineering, you can't stop it. 

---

Solutions

• Design to live within the flexible island environment. Don't fight nature.
• Consider all man-made structures near the shore as temporary
• Accept as a last resort any engineering scheme fro beach restoration or preservation, and then, only for metropolitan areas.
• Base decisions affecting island development on the welfare of the public rather than the minority of shorefront property owners. 

Barrier island "safety criteria"

• Erosion rate (front and back sides)
• Elevation
• Island width and position relative to the shore
• Soil type
• Storm response (dune stability)
• Inlet proximity
• Vegetation
• Storm frequency

Questions:

The following questions are based on material from Hansen (1973) and Dean (1999).

• According to Gunnar Hansen Louisiana loses an average 16.9 feet of land per year. List and explain all the factors contributing to this loss.
  • Discuss the economic ramifications of this loss.
  • Shea Pendland has defined a model that includes three stages or transitions a delta lobe undergoes after is has been abandoned. What are these?
  • How has the engineering of the the Mississippi River and its delta contributed to the problem of coastal erosion in this region.
• Contrast the morphology of Padre Island and the Sea Islands of South Carolina. Discuss why these barrier systems are so different.
• Oregon inlet. Briefly review the history of this inlet. Why is the inlet so controversial?
• What is meant by "New Jerseyization? What are the consequences of this form of coastal armoring? Cite examples.
• The building of artificial dunes were always thought to be non invasive erosion management technique.
• What is the function of the following structures: jetties, groins, seawalls, and breakwaters. Discuss the environmental consequences of each.
• Discuss the relationship between the rate of barrier island migration with the slope of the continental shelf and sea level rise. What is the predicted rate of retreat of barriers around Pamlico Sound, NC?
• What is a littoral cell as defined by Inman (in Dean, 1999). What effect would the stabilization of an eroding sea cliff, the construction of jetties, or building of a dam have on a littoral cell. What kind of political problems does this effect introduce?

[GeoHotsitesHome][GeoIndex][QkRef][GLS214]

Lindley Hanson/email /Gls214

Department of Geological Sciences, Salem State College, Salem, MA
last updated 5/19/03