ABSTRACT

Each of four size classes of foreshore sand from Sandy Hook, New Jersey, was color coded with daylight and ultraviolet fluorescent coating material. These tracer particles were introduced at mid-swash line on the foreshore surface at Kingmill Beach, Sandy Hook, two hours prior to high tide. During the test Atlantic Ocean waves approaching at an angle of approximately 5 degrees to the shoreline caused 5.3-second breakers of 0.73 meter maximum height. In a time-integration procedure samples were obtained by channel sampling on the foreshore along a sampling line, transverse to the foreshore, that was established 30.5 meters downdrift from the point of introduction of tracer particles.

Sub-samples of the 18 samples taken during the 49.7 minutes after marked particle introduction were examined for tracer particle content. Recovery data indicate particles in the smallest size class (0.701 >d>0.589 mm) began arriving at sampling line 18.2±0.7 minutes after introduction: equivalent to 2.8 cm/sec average maximum transport velocity. Particles in the next largest size class began arriving 25.8±1.7 minutes after introduction: equivalent to 2.0 cm/sec average maximum transport velocity. However, a maximum number of marked particles in both size classes was found in a sample taken 42.3 minutes after introduction. Only one particle in each of the two larger size classes (1.397 > d > 1.168 and 1.168 > d >0.991 mm) was recovered.

Particle-recovery distribution is assumed to be influenced by sample size and total weight of particles in each size class containing marked particles. Converted particle-recovery distribution is based on weight ratio of marked particles to total particles in each appropriate size class. These data show a 3.2-minute delay in peak arrival of particles in size class 0.840>d>0.701 mm relative to peak recovery of particles in size class 0.701 > d > 0.589 mm. Therefore, for these two size classes both first arrival and converted peak arrival data indicate an inverse size-velocity relationship prevails in beach drift transport.