ERDC/CHL CHETN-II-47
March 2004
a focused examination of the potential for hot spot development. Identifying the potential for hot
spot occurrence in the feasibility or design phase of project development will enable design modifi-
cations to address the hot spot area, provide a more accurate estimate of project costs and perform-
ance, and educate project shareholders and sponsors about the potential for nonuniform project
performance. Realistic expectations about possible hot spot occurrence will help to eliminate the
perception of poor project performance or inadequate project design.
Often the presence of an erosional hot spot is evident prior to project construction. However, in some
cases the existence of a hot spot may not be apparent due to the eroded state of the preproject beach.
That is, the preproject dry beach width may be sufficiently narrow or, in fact, nonexistent, which can
mask the signal of the erosional hot spot. Data and analysis tools are typically available to aid the
examination of the potential for hot spot development. These include historic records of shoreline
position and shoreline rates of change, detail nearshore hydrographic survey data, and numerical
models for nearshore wave transformation (STWAVE) and shoreline evolution (GENESIS). Based
on the case study summary information listed in Table 4, it is seen that wave focusing by nearshore
bathymetric irregularities or coastal structures is the most frequently identified cause for hot spot
development. Underlying geology is the next most frequently identified cause for hot spot develop-
ment (which may also influence wave focusing) followed by inlet effects, structure-induced impacts,
end effects, and development encroachment on the active beach. Investigation of underlying geology
using cores, subbottom seismic and sidescan survey mosaics, and review of the coastal geologic
literature will improve the discovery of geologic controls on hot spot occurrence.
Table 4
Project Hot Spot Summary Data
Project
#
Type
Cause
Remedial Action
Coney Island, NY
1
Updrift barrier/wave focusing Terminal groin/nearshore
Sand bypass/additional
shoal induced wave focusing
groins proposed
Sea Bright Manasquan, NJ
1
Monmouth Beach -
Seaward displacement of fill
Additional fill added -
encroachment/temp. terminal material/end losses
resolved w/ next reach filled
end
2
Spring Lake - updrift
Groin too long/ nearshore
Notch groin/add coarser fill
barrier/nearshore bathymetry contour change/finer borrow
material
3
Sea Bright - terminal end
End losses
Renourishment
Ocean City, NJ
1
Wave focusing/drift reversal
Borrow pit/ebb shoal
Renourishment/modify
borrow area dredge location
away from beach
th
Ocean City, MD
1
15 St. - shoreline orientation Change in shoreline
Renourishment
orientation
nd
2
32 St. - encroachment
Upland property is seaward
Renourishment/ backpassing
nd
3
52 St. - nearshore
Shore-attached shoal wave
Renourishment overfill/
bathymetry variation
focusing
backpassing
st
4
81 St. - nearshore
Shore-attached shoal wave
Renourishment overfill/
bathymetry variation
focusing
backpassing
th
5
146 St. - terminal end
End losses
Change taper
Bogue Banks, NC
1
Inlet - wave focusing/drift
Wave focusing over ebb
Periodic navigation channel
reversal
shoal
disposal placement
(Navigation channel dredge
disposal)
(Continued)
Note: ? = possible cause, exact cause unknown.
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