In: Proceedings Coastal Sediments '03. 2003. CD-ROM Published by World Scientific Publishing
Corp. and East Meets West Productions, Corpus Christi, Texas, USA. ISBN 981-238-422-7.
equilibrium. After significant dredging and raising the mean tide level north jetty to an above high
water elevation, severe channel shoaling was reduced and the area increased to that shown for 1991
(see Fig. 2). The 1991 channel area falls on the left side of the Escoffier diagram, indicating its
potential to move to the right toward equilibrium. The 1998 area reflects measurements taken after
the old arrowhead jetties were streamlined to a parallel jetty system. The area has shifted further
along the curve towards stable equilibrium. The equilibrium area from the graphical analysis for the
existing bay is a very large 15,000 m2 (see Figure 2). Given that the existing Keulegan K is less than
the 0.6 to 0.8 range for K, and is much less than Escoffier equilibrium, it is concluded that the inlet is
not in equilibrium. A short history of tidal prisms for Barnegat inlet (Fig. 4) shows that recent inlet
prisms and thus inlet cross-section has been in this range of K for many years. There is variation that
was due to improvements in the jetties and reduction in channel shoaling plus dredging. This system
has a long entrance channel (see Figure 3) and perhaps the friction dominates and has helped keep
the K value low (see Eq. 2). However, with recent improvements, a scouring mode seems to be
occurring. The important question is how much scour will occur. Accepting the result of the basic
Escoffier analysis, a considerable amount of scour may occur.
Table 1. Examples of "Low Keulegan K" Inlets
*
In the United States
Inlet
Keulegan K Value
New River, NC
0.08
Barnegat, NJ
0.09
Shinnecock, NY
0.15
Ft. Pierce, FL
0.16
Chincoteague, VA
0.16
St. Johns, FL
0.21
Indian River, DE
0.22
Ponce de Leon, FL
0.25
St. Lucie, FL
0.26
Ocean City, MD
0.29
Beach Haven, NJ
0.31
Jones, NY
0.35
Beaufort, NC
0.41
North Edisto, SC
0.42
Jupiter, FL
0.44
Winyah Bay, SC
0.45
Bakers Haulover, FL
0.45
Moriches, NY
0.54
Manasquan, NY
0.65
*
Values are historical and may not accurately represent today's value.
Applying the criteria of Mota Oliveira that equilibrium would likely be in the Keulegan K range of
0.6 to 0.8, it can be determined from a simple one-dimensional model based on DiLorenzo (1988)
and implemented in a PC based program for the Escoffier analysis (Seabergh and Kraus 1997), that
the cross-sectional area for a value of K equal to 0.8 is 4,300 m2. The resultant cross section would
be different than the equilibrium area, found in Figure 2, of 15,000 m2.
Determining the response ability of the channel area as discussed earlier and based on Figure 2 for
Barnegat Inlet, it is seen that a channel area of about 10,000 m2 has the highest value. This would
Seabergh
4
Previous Page
