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Shelf Width, Shoreline Curvature, and Hurricanes: Continued Development of a New Hurricane Impact Scale David M. Bush 1, Robert S. Young 2 , and Chester W. Jackson 1 1 State University of West Georgia 2 Western Carolina University
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David M. Bush1, Robert S. Young2, and Chester W. Jackson1
1State University of West Georgia
2Western Carolina University
Several similarly sized hurricanes have hit the North Carolina coast in recent years with very different impacts.
Some of the difference is due to the shoreline setting. Here is the retreating shoreline and overwash apron of Oak Island.
Bogue Banks, meanwhile, is a higher sand volume island, retreating bluff setting.
The classical way to rank hurricanes is the Saffir-Simpson Scale, fine for hurricanes over open water but
not so good with predicting erosion and overwash impacts at landfall.
The Hurricane Impact Scale would consider storm surge height and storm surge spread (length of shoreline
affected), as well as the Saffir-Simpson Scale, to rank hurricanes.
The important controls on storm surge at landfall are: (1) storm physical characteristics, (2) movement of
the storm, and (3) shape of the shoreline relative to storm track.
important controls on storm surge:
Wide shelf = higher storm surge
Narrow shelf = lower storm surge
Concave shoreline = higher storm surge
Straight or convex shoreline = lower
Hurricane Opal hit a curved stretch of the Florida panhandle in 1995 and clearly shows a classic storm surge
profile on a shoreline with a curvature at a scale matching the size of the hurricane.
Applying the HIS for recent major storms shows that the impacts of the storms at landfall were at scales
somewhat different than their Saffir-Simpson Scale category rankings.
Curvature = C/P
Future work calls for applying a shoreline curvature parameter. Shoreline curvature may be quantified by dividing the chord length (C) by the perpendicular length (P) for various coastal segments.
The ratio of shelf width (light blue line) to shoreline curvature (C/P) yields a width/curvature index (white numbers). This index has yet to be incorporated into the HIS.
Shoreline curvature (at several scales)
Predicted storm track
Predicted storm strength
Predicted storm forward speed
Range of HIS scales
Wind speeds NHC/NWS
Single HIS rank assignedHIS Modes
With shoreline settings quantified, local coastal managers will be able to predict the range of possible landfall impacts of a hurricane for their particular stretch of shoreline, given the National Hurricane Center’s predicted strength of the hurricane.