SUROB. If several breaker angles exist and breaker
lines are moving toward both flanks, the following entry
is made: 10-20 toward R/L flank. If the breakers are
directly parallel to the beach, the entry should be: 0
toward R/L flank.
During amphibious operations, how are
individual beach sections identified?
How is significant breaker height determined in
a surf observation?
Plunging breakers are associated with what type
What type of breakers would you expect to find
on a beach with a very steep slope?
How do you determine the direction breakers are
Littoral Current (FOXTROT)
The littoral current must be measured and reported
in each SUROB. The littoral current, also called the
longshore current, is the current produced by the
transport of the water caused by the breaking action of
the waves. As the waves approach the shore at an angle,
water is pushed up onto the beach at the same angle, and
generates a net flow of water or a current. This current
runs parallel to the beach and may be amplified by the
presence of a longshore sandbar. Littoral currents are
significant in that they can cause landing craft to drift
off course and miss designated landing areas. Littoral
currents are more common on straight beaches.
The velocity of a littoral current will normally be
higher on beaches with steep slopes, and will increase
with increasing breaker height and breaker angle.
Velocities may reach speeds of 3 to 4 knots. Tidal
currents parallel to the shore may intensify the littoral
current or create opposing offshore currents. The speed
and direction of the littoral current are reported in
section FOXTROT of the SUROB.
MEASURING LITTORAL CURRENTS.the
measurement of speed and direction of the littoral
current is fairly simple. Throw a piece of wood or other
debris in the surf immediately in front of the inner most
breaker, and pace off the distance in feet that it moves in
1 minute. The distance traveled by the debris in 1
minute divided by 100 is the speed of the littoral current
in knots (10 feet of travel is equal to 0.1 knot). Several
measurements should be made and the average reported
to the nearest 0.1 knot. The direction of movement, or
set of the littoral current, must also be reported as
toward the left or right flank of the beach, as seen from
RIP CURRENTS.Rip currents are formed
when opposing offshore currents bend sections of a
littoral current seaward, creating rip currents (popularly
but erroneously called riptides). Rip currents are caused
by water piling up along the shore. The water flows
parallel to the shore for a short distance until it meets an
opposing current or is deflected by bottom
irregularities. Rip currents consist of three parts, the
feeder current or currents which flow. parallel to the
beach inside the breaker zone, the neck where the feeder
current or currents converge and flow through the
breakers in a narrow band or rip, and the head where the
current widens and slackens outside the breaker line.
Cusps (points) forming in the beach sand indicate rip
currents are forming (fig. 4-7). An observer can usually
distinguish a rip current as a stretch of unbroken water
in the breaker zone where no breakers occur. The outer
limit of the current in the head is usually marked by
patches of foam and broken water similar to tide rips,
and the head itself is usually discolored by suspended
Although rip currents commonly exceed 0.5 knot
(the sustained speed of a trained swimmer) and should
be avoided by swimmers, rip currents frequently cut a
deep channel perpendicular to the beach, which creates
an area where the breaker heights are significantly
lower than the prevailing surf. Rip current channels
may, in rare cases, provide the easiest route through a
surf zone for certain landing craft.
The presence of rip currents should be noted as a
remark in element HOTEL of the SUROB report. In the
rip current, the significant breaker height, ALFA, and
maximum breaker height, BRAVO, should also be
reported as a remark in element HOTEL. A position
relative to the beach center may also be included. For
example, the rip current may be reported as RIP
CURRENT CHANNEL LEFT FLANK RED 30 YD
WIDE ALFA 1 PT 5 BRAVO 2 PT 0.