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. Q11. Q12. Q13. Q14. Q15. REVIEW  QUESTIONS 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 of waves? 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 moving? 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 seaward. 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 silt. 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. 4-8