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REVIEW QUESTIONS
What publication outlines procedures for
conducting surf observations?
What are two factors that can create surf?
What are the boundaries of the surf zone?
When a wave enters shallow water, what
happens to the wave speed, wavelength, and
wave height?
How is wave steepness defined?
The hydrography in a surf zone includes what
elements?
How does the presence of a sandbar effect waves
moving into a surf zone?
What descriptive term is used to classify a beach
with a slope of 1:25?
What affect might a sandbar have on small craft
operations?
What is meant by the term "wave refraction"?
THE SURF OBSERVATION
LEARNING OBJECTIVES: Describe the
procedures used to observe surf conditions.
Describe how to record and transmit surf
observations.
Surf observers report surf conditions by using a
special code. Individual surf elements are reported by
using standard designators, such as ALFA (to indicate
significant breaker height), BRAVO (to indicate
maximum breaker height), and so on. Surf forecasts
(SURFCSTS) are issued in the same format and are just
one part of the Amphibious Objective Area Forecast
(AOAFCST) produced by forecaster personnel.
SUROBs are recorded on a locally reproduced SUROB
worksheet (fig. 4-3).
BEACH FAMILIARIZATION
During amphibious operations, beaches are
identified by color codes. A 3-mile-long section of
beach, for example, may be broken down into shorter
sections identified as Red Beach, Purple Beach, or
Green Beach. Normally, even on an irregular coastline,
planners try to divide the larger beaches into sections
with similar characteristics. The orientation of the
beach and the beach slope should be fairly uniform for a
beach called Green Beach, even though an adjacent
beach area, perhaps called Red Beach, may have a
dramatically different orientation and slope. In addition
to color designations, beaches may also be identified by
letter abbreviations alone. When tasked to provide
SUROBs, you, the observer, must first familiarize
yourself with the beach designations and boundaries
involved, since separate observations may be required
for each beach area.
SURF OBSERVATION ELEMENTS
The SUROB worksheet is completed (and saved)
for each individual SUROB. The observation number,
the date and time of the observation (in UTC), and the
beach identification are entered on each form as the first
part of each SUROB report.
Breaker Height (ALFA/BRAVO)
When observing the surf, you must observe the
breaker heights of 100 individual breakers. Normally,
breaker height is evaluated in an area where the waves
are breaking nearest the beach. Breaker height is
estimated to the nearest half-foot and is entered in the
Wave Height Observation blocks on the SUROB
worksheet. After observing 100 individual breakers,
enter the significant breaker height, which is the
average height of the highest one-third of all the
observed breakers. Enter to the nearest 1/2 foot, as
element ALFA on the SUROB report. Enter the
maximum breaker height (the height of the single
highest breaker observed) to the nearest 1/2 foot as
element BRAVO.
Breaker heights are usually best estimated from a
position close to the waterline on the beach. One fairly
accurate method for estimating breaker height calls for
the observer to line up the top of the breaker crest with
the horizon. The height of the breaker is the vertical
distance from this line to the seaward edge of the uprush
zone. The uprush zone is the area on the beach where
the waves cause the water to temporarily rush up on the
sand, and then recede on the wave backwash to expose
the sand. This method becomes less accurate as the
distance from the observer to the breakers increases.
See figure 4-4.
In cases where a longshore sandbar is present, the
highest breakers may occur over the sandbar, with only
smaller breakers occurring near the beach. This is the
case at low tide. If you observe higher, more significant
breakers offshore (over a submerged sandbar), enter
4-4
