The quality and quantity of available data often do not justify
elaborate statistical analysis. Even where adéquate data are available,
a simple characterization of wave climate meets many engineering needs.
While mean values of height and, to a lesser degree, period are useful,
data on wave direction are generally of insufficient quality for even
mean value use. Table 4-4 compiles mean annual wave heights collected
from a number of wave gages and by Visual observers along the coasts of
the United States. Visual observations were made from the beach of waves
near breaking. The gages were fixed in depths of 10 to 28 feet.
Wave data treated in this section are limited to nearshore observations and measurements. Consequently waves were fully refracted and had
been fully affected by bottom friction, percolation, and nonlinear changes
in wave form by shoaling. Thus, these data differ from data that would
be obtained by simple shoaling calculations based on the deepwater wave
statistics. In addition, data are normally lacking for the rarer, highwave events. For these reasons, the data should not be used for structural design, since they are only applicable to the particular site
where they were obtained. Normal design practice is based on deepwater
wave statistics which are then adjusted to the shallow-site conditions.
However, the nearshore data are useful in littoral transport calculations.
Mean wave height and period from a number of visual observations by
coastguardmen at shore stations are plotted by month in Figures 4-10 and
4-11, using the average values of stations within each of five Coastal
segments. Table 4-4 and Figures 4-10 and 4-11 show average values characteristic of the wave climate in exposed Coastal localities. Visual
height data represent an average value of the higher waves just before
they first break. The data provide only approximate indications of the
height distributions, but mean values of these distributions are useful.
In Figure 4-10 the minimum monthly mean littoral zone wave height
averaged for the California, Oregon, and Washington coasts exceeds the
maximum mean littoral zone wave height averaged for the other coasts.
This différence greatly affects the potential for sédiment transport in
the respective littoral zones, and should be considered by engineers
uhen applying expérience gained in a locality with one nearshore wave
climate to a problem at a locality with another wave climate.
4.332 Mean vs Extrême Conditions. Section 3.22 contains a discussion
of wave height distributions and the relations between varions wave
height statistics, such as the mean, significant, and RMS heights, and
extreme values. In general, a group of waves from the same record can be
approximately described by a Rayleigh distribution. (See Section 3.22.)
owever, a different distribution appears necessary to describe the dis^ri ution of significant wave heights, where each significant wave height
is trom a different wave record at the locality. (See Figure 4-12.)
Visual analysis of waves recorded on chart paper is discussed in
DraPer C196?), Tucker (1963), Harris (1970), and
). Spectrum analysis of wave records is discussed in
4-30
elaborate statistical analysis. Even where adéquate data are available,
a simple characterization of wave climate meets many engineering needs.
While mean values of height and, to a lesser degree, period are useful,
data on wave direction are generally of insufficient quality for even
mean value use. Table 4-4 compiles mean annual wave heights collected
from a number of wave gages and by Visual observers along the coasts of
the United States. Visual observations were made from the beach of waves
near breaking. The gages were fixed in depths of 10 to 28 feet.
Wave data treated in this section are limited to nearshore observations and measurements. Consequently waves were fully refracted and had
been fully affected by bottom friction, percolation, and nonlinear changes
in wave form by shoaling. Thus, these data differ from data that would
be obtained by simple shoaling calculations based on the deepwater wave
statistics. In addition, data are normally lacking for the rarer, highwave events. For these reasons, the data should not be used for structural design, since they are only applicable to the particular site
where they were obtained. Normal design practice is based on deepwater
wave statistics which are then adjusted to the shallow-site conditions.
However, the nearshore data are useful in littoral transport calculations.
Mean wave height and period from a number of visual observations by
coastguardmen at shore stations are plotted by month in Figures 4-10 and
4-11, using the average values of stations within each of five Coastal
segments. Table 4-4 and Figures 4-10 and 4-11 show average values characteristic of the wave climate in exposed Coastal localities. Visual
height data represent an average value of the higher waves just before
they first break. The data provide only approximate indications of the
height distributions, but mean values of these distributions are useful.
In Figure 4-10 the minimum monthly mean littoral zone wave height
averaged for the California, Oregon, and Washington coasts exceeds the
maximum mean littoral zone wave height averaged for the other coasts.
This différence greatly affects the potential for sédiment transport in
the respective littoral zones, and should be considered by engineers
uhen applying expérience gained in a locality with one nearshore wave
climate to a problem at a locality with another wave climate.
4.332 Mean vs Extrême Conditions. Section 3.22 contains a discussion
of wave height distributions and the relations between varions wave
height statistics, such as the mean, significant, and RMS heights, and
extreme values. In general, a group of waves from the same record can be
approximately described by a Rayleigh distribution. (See Section 3.22.)
owever, a different distribution appears necessary to describe the dis^ri ution of significant wave heights, where each significant wave height
is trom a different wave record at the locality. (See Figure 4-12.)
Visual analysis of waves recorded on chart paper is discussed in
DraPer C196?), Tucker (1963), Harris (1970), and
). Spectrum analysis of wave records is discussed in
4-30