Irrigation of Submerged Marine Sands through Wave Action

Abstract

PRELIMINARY tests carried out on the permanently submerged amphioxus sands at Le Racou (Roussillon) on the Mediterranean coast of France on August 27, 1968, have shown that turbulence and differences in hydrostatic pressure at the seabed caused by the passage of surface waves produce water movements in permeable deposits. These chiefly quartz sands were at a depth of 3 m and had the approximate grain size distribution, determined from samples taken from the area at this depth, shown in Table 1. Sand ripples ran north to south across the line of approach of the waves of maximum fetch from the east and were approximately parallel to the shore. The crests of the ripples were 75 cm apart and separated by a more or less flat trough 30 cm broad. The height from trough to crest of the ripple was 12–15 cm. The hand could be thrust into the sand without excessive resistance to a depth of about 7.5 cm on the crest of the ripple and 5 cm in the trough, indicating unconsolidated conditions to these depths. It was relatively calm at the time of the test, the wave direction being from the east, that is across the sand ripples, and the wave height from trough to crest about 50 cm.