storm level or high-tide level (Semeniuk and Johnson,
1982; Semeniuk, 1997). Tidal currents perform the same
functions of transporting, reworking, and winnowing sediment, creating distinctive lithologic and stratigraphic
suites.
Because the provenance of shoreline sediment is variable (reworked from barrier dunes or flood-tidal deltas,
and hence marine-derived, reworked as fans, shoestrings,
or ribbons from the uplands bordering the estuary, riverine, or generated biogenically), clearly, the sediment type
underlying an estuarine beach will vary compositionally
and granulometrically (fine sand to coarse sand to gravel
and with variable shell content) and, depending on the
short-term history of prevailing wave action, storm waves,
and tides, will carry a distinctive small-scale stratigraphic
signature such as shell gravel lenses interlayered with laminated sand, or coarse sand interlayered with medium/fine
sand, or pebble layers in laminated sand, among others.
During a high tide, the beach slope is inundated and the
beach sands are saturated. During the ensuing low tide
when the beach is subaerially exposed, there are two
sub-environments where water resides under a beach:
(1) shallow groundwater (that is contiguous with the open
waters) whose water table falls and rises with the tide; this
Beach Processes, Figure 5 Some profiles of beaches in estuaries. (a) Microtidal, steep beach backed by rock, at Botany Bay entrance,
southeastern Australia. (b) Microtidal, moderately sloping beach fronted by wide, sandy tidal flat and backed by low dunes, Sans
Souci, Botany Bay, southeastern Australia. (c) Narrow, microtidal beach in front of a dune barrier, Nornalup Inlet estuary, southern
Western Australia (From Semeniuk et al., 2011). (d) Narrow, microtidal, steep beach in the front of beach ridges of the Deep River
Delta, Nornalup Inlet estuary, southern Western Australia (From Semeniuk et al., 2011). (e) Narrow, microtidal, steep beach in the front
of a bar-and-lagoon complex, with a peat-filled lagoon to leeward, Nornalup Inlet estuary, southern Western Australia (From
Semeniuk et al., 2011). (f) Narrow, microtidal beach in front of the Collie River Delta, Leschenault Inlet estuary (From Semeniuk, 2000).
60
BEACH PROCESSES
1982; Semeniuk, 1997). Tidal currents perform the same
functions of transporting, reworking, and winnowing sediment, creating distinctive lithologic and stratigraphic
suites.
Because the provenance of shoreline sediment is variable (reworked from barrier dunes or flood-tidal deltas,
and hence marine-derived, reworked as fans, shoestrings,
or ribbons from the uplands bordering the estuary, riverine, or generated biogenically), clearly, the sediment type
underlying an estuarine beach will vary compositionally
and granulometrically (fine sand to coarse sand to gravel
and with variable shell content) and, depending on the
short-term history of prevailing wave action, storm waves,
and tides, will carry a distinctive small-scale stratigraphic
signature such as shell gravel lenses interlayered with laminated sand, or coarse sand interlayered with medium/fine
sand, or pebble layers in laminated sand, among others.
During a high tide, the beach slope is inundated and the
beach sands are saturated. During the ensuing low tide
when the beach is subaerially exposed, there are two
sub-environments where water resides under a beach:
(1) shallow groundwater (that is contiguous with the open
waters) whose water table falls and rises with the tide; this
Beach Processes, Figure 5 Some profiles of beaches in estuaries. (a) Microtidal, steep beach backed by rock, at Botany Bay entrance,
southeastern Australia. (b) Microtidal, moderately sloping beach fronted by wide, sandy tidal flat and backed by low dunes, Sans
Souci, Botany Bay, southeastern Australia. (c) Narrow, microtidal beach in front of a dune barrier, Nornalup Inlet estuary, southern
Western Australia (From Semeniuk et al., 2011). (d) Narrow, microtidal, steep beach in the front of beach ridges of the Deep River
Delta, Nornalup Inlet estuary, southern Western Australia (From Semeniuk et al., 2011). (e) Narrow, microtidal, steep beach in the front
of a bar-and-lagoon complex, with a peat-filled lagoon to leeward, Nornalup Inlet estuary, southern Western Australia (From
Semeniuk et al., 2011). (f) Narrow, microtidal beach in front of the Collie River Delta, Leschenault Inlet estuary (From Semeniuk, 2000).
60
BEACH PROCESSES