. Collected reprints / Atlantic Oceanographic and Meteorological Laboratories [and] Pacific Oceanographic Laboratories. Oceanography THE SHOREFACE PROFILE 267 grain sizes associated with observed shoreface profiles. For instance, modern coasts whose historical records in- dicate that they are undergoing erosional retreat tend to consist of two distinctive grain provinces. From the breaker to a depth of about 10 m, the upper shoreface consists of fine, seaward-fining sand (Fig. 8). Seaward of 10 m, grain size on the lower shoreface and adjacent shelf floor is far more variable and
. Collected reprints / Atlantic Oceanographic and Meteorological Laboratories [and] Pacific Oceanographic Laboratories. Oceanography THE SHOREFACE PROFILE 267 grain sizes associated with observed shoreface profiles. For instance, modern coasts whose historical records in- dicate that they are undergoing erosional retreat tend to consist of two distinctive grain provinces. From the breaker to a depth of about 10 m, the upper shoreface consists of fine, seaward-fining sand (Fig. 8). Seaward of 10 m, grain size on the lower shoreface and adjacent shelf floor is far more variable and generally markedly coarser. We may account for the fine, upper shoreface sand province as a mantle of rip current fallout, whose slope is adjusted by the regime of shoaling waves (Cook, 1969). However, the lower shoreface province of coarse variable sand does not fit the model for wave mainte- nance of the shoreface. We may consider the hypothesis that it is instead a response to the deeper, intermittent high-intensity flows of the zone of friction-dominated flow (Figs. 2B and 6B, C). Observations by Moody (1964, pp. 142-154) on the erosional retreat of the Delaware coast lend some sup- port to this hypothesis (Fig. 9). In this area, the shore- face steepens over a period of years toward the ideal wave-graded profile, during which time the shoreline remains relatively stable. The steepening is both a de- positional and erosional process. Moody notes that steep- ening was accelerated after 1934 because a groin system initiated then "presumably trapped sand, causing the upper part of the barrier between mean low water and — 3 m to build seaward" (Moody, 1964, p. 142). How- ever, erosion continued offshore at depths of 6 or 7 m below mean low water. The steepening process is not continuous, but varies with the frequency of storms and duration of intervening fair-weather periods. The slope of the barrier steepened from 1:40 to 1:25 between 1929 and 1954, but erosion on
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