ERDC/CHL CHETN-II-47
March 2004
Table 2
Hot Spot Identification II (from Bodge, Gravens, and Srinivas 1999)
No.
Type
Cause
1
Wave focusing
Offshore/nearshore bathymetry; shoreline orientation.
2
Shoreline orientation
Abrupt change in orientation; headlands; Shoreline declination relative to
dominant wave angle.
3
Encroachment
Upland development near, at, or seaward of historic natural beach, may require
fill further seaward to provide protection.
4
Offshore sinks (canyons, relict borrow
Loss to beach system.
areas, rips etc.)
5
Sediment starvation
Block longshore drift (i.e., jetty, groin, seawall, etc.).
6
Design deficiencies or irregularities in
Placement of less than required fill density; irregular fill planform.
prior beach fill
7
Taper and end effects
End loss high due to less fill and taper angle.
8
Rhythmic topography, irregular
Cyclical variation; erosion waves pass through project.
nearshore hardbottoms
An interaction of coastal processes with coastal morphology leads to the cause of erosion hot spots.
The causes listed in the Tables 1 and 2 can be summarized into the following
a. Coastal processes (waves, currents and longshore drift).
b. Geologic controls (underlying geology; hardbottoms including reefs or beachrock;
morphology such as headlands or embayments; and bathymetry for example shoals, canyons
or channels).
c. Inlet processes (sand bypassing, ebb and flood shoal evolutions, and channel migration).
d. Anthropogenic activity (structures including seawalls, groins/jetties, breakwaters; dredging
of channels and borrow areas; upland construction practices; and fill placement).
e. Combinations of a-d (wave focusing refraction over bathymetric feature and/or shoreline
orientation abrupt change due to underlying geology).
Enchroachment on the shoreline (development seaward of the historic shoreline or on
f.
ephemeral accreted lands).
A series of case studies of hot spots associated with either proposed or constructed beach nourish-
ment projects are examined in an effort to identify the most frequently occurring types of hot spots
and to characterize the processes known or suspected to be responsible for their formation.
CASE STUDIES OF PROJECT HOT SPOTS: Twenty-nine participants attended a workshop
held in Baltimore, MD, on 19-20 March 2003 from the Atlantic, Gulf of Mexico, Pacific, and Great
Lakes Coastal Districts, Divisions, Headquarters, and the U.S. Army Engineer Research and
Development Center (ERDC), Coastal and Hydraulics Laboratory (CHL). The purpose of the
workshop was to discuss field experiences related to project vulnerabilities resulting from the
formation of hot spots and other post-storm erosion conditions on recent beach nourishment projects.
Workshop presentations included: (a) how hot spots were identified, (b) what remedial actions were
taken, and (c) realized project vulnerabilities. Nine District Offices presented case studies and 20
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