Historical records of shoreline changes are usually in the form of
charts, surveyed profiles, dredging reports, beach replenishment reports
and aerial photos. As an example of such historical data, Figure 4-52
shows the positions of the shoreline at Sandy Hook, New Jersey, during
six surveys from 1835 to 1932. Such shoreline changes are useful for
computing longshore transport rates. The Corps of Engineers maintains,
in its District and Division offices, survey, dredging, and other reports
relating to Corps projects. Charts may be obtained from varions fédéral
agencies including the Defense Mapping Agency Hydrographie Center, Geological Survey, National Océan Survey, and Defense Mapping Agency Topographie
Center. A map called "Status of Aerial Photography," which may be obtained
from the Map Information Office, Geological Survey, Washington, D.C. 2024*2,
shows the locations and types of aerial photos available for the U.S., and
lists the sources from which the photos may be requested. A description of
a coastal imagery data bank can be found in the intérim report by Szuwalski
(1972).
Other kinds of data usually available are wave, tide, and meteorological data. Chapter 3 discusses wave and water level prédictions; Section 4.3 discusses the effects of waves on the littoral zone; and Subsection 4.34 présents methods of estimating wave climate and gives possible sources of data. These referenced sections indicate the wave, tide,
and storm data necessary to evaluate Coastal engineering problems.
Additional information can be obtained from local newspapers, courthouse records, and from area residents. Local people can often identify
factors that outsiders may not be aware of, and can also provide qualititive information on previous coastal engineering efforts in the area
and their effects.
4.812 Interprétation of Shoreline Position. Preliminary interprétation
of littoral processes is possible from the position of the shoreline on
aerial photos and charts. Stafford (1971) describes a procedure for utilizing periodic aerial photographs to estimate coastal érosion. Used in
conjunction with charts and topographie maps, this technique may provide
quick and fairly accurate estimâtes of shoreline movement, although the
results can be biased by the short-term effects of storms.
Charts show the coastal exposure of a study site, and since exposure
détermines the possible directions from which waves reach the coast, exposai e also détermines the most likely direction of longshore transport.
Direction of longshore transport may also be indicated by the position of sand accumulation and beach érosion around littoral barriers. A
coastal structure in the surf zone may limit or prevent the movement of
sand, and the buildup of sédiment on one side of the littoral barrier serves as an indicator of the net direction of transport. This buildup can be
determined from dredging or sand bypassing records or aerial photos. Figure 4-53 shows the accumulation of sand on one side of a jetty. But wave
direction and nearshore currents at the time of the photo indicate that
transport then was in the opposite direction. Thus, an erroneous conclusion
4-140
charts, surveyed profiles, dredging reports, beach replenishment reports
and aerial photos. As an example of such historical data, Figure 4-52
shows the positions of the shoreline at Sandy Hook, New Jersey, during
six surveys from 1835 to 1932. Such shoreline changes are useful for
computing longshore transport rates. The Corps of Engineers maintains,
in its District and Division offices, survey, dredging, and other reports
relating to Corps projects. Charts may be obtained from varions fédéral
agencies including the Defense Mapping Agency Hydrographie Center, Geological Survey, National Océan Survey, and Defense Mapping Agency Topographie
Center. A map called "Status of Aerial Photography," which may be obtained
from the Map Information Office, Geological Survey, Washington, D.C. 2024*2,
shows the locations and types of aerial photos available for the U.S., and
lists the sources from which the photos may be requested. A description of
a coastal imagery data bank can be found in the intérim report by Szuwalski
(1972).
Other kinds of data usually available are wave, tide, and meteorological data. Chapter 3 discusses wave and water level prédictions; Section 4.3 discusses the effects of waves on the littoral zone; and Subsection 4.34 présents methods of estimating wave climate and gives possible sources of data. These referenced sections indicate the wave, tide,
and storm data necessary to evaluate Coastal engineering problems.
Additional information can be obtained from local newspapers, courthouse records, and from area residents. Local people can often identify
factors that outsiders may not be aware of, and can also provide qualititive information on previous coastal engineering efforts in the area
and their effects.
4.812 Interprétation of Shoreline Position. Preliminary interprétation
of littoral processes is possible from the position of the shoreline on
aerial photos and charts. Stafford (1971) describes a procedure for utilizing periodic aerial photographs to estimate coastal érosion. Used in
conjunction with charts and topographie maps, this technique may provide
quick and fairly accurate estimâtes of shoreline movement, although the
results can be biased by the short-term effects of storms.
Charts show the coastal exposure of a study site, and since exposure
détermines the possible directions from which waves reach the coast, exposai e also détermines the most likely direction of longshore transport.
Direction of longshore transport may also be indicated by the position of sand accumulation and beach érosion around littoral barriers. A
coastal structure in the surf zone may limit or prevent the movement of
sand, and the buildup of sédiment on one side of the littoral barrier serves as an indicator of the net direction of transport. This buildup can be
determined from dredging or sand bypassing records or aerial photos. Figure 4-53 shows the accumulation of sand on one side of a jetty. But wave
direction and nearshore currents at the time of the photo indicate that
transport then was in the opposite direction. Thus, an erroneous conclusion
4-140