Soft sediment coasts sandy shores, sand dunes, marsh lands and estuarine shores Frances Mowling Coastal & Aeolian Geomorphology
Soft landforms 3 Dune forms Foredunes ± incipient dunes Parallel dunes Transgressive dunes Spits, barriers Estuaries, lacustrine systems Embayed beaches
Coastal Dunes Foredune and Parallel Foredune and parallel dune forms are common landforms. Parallel dunes are sometimes called secondary dunes, in that the foredune is the first dune located at the backshore of the beach, and parallel dunes are located behind the foredune. Good examples: Templestowe and Lagoons Beaches, Binalong Bay, Taylors, Boobyalla, and Waterhouse Beaches, Noland Bay.
Transgressive dunes Transgressive dunes Peron Dunes St Helens, Cape Portland to Great Forester River, Sandy Point, St Albans Bay, and Five Mile Bluff.
Foredune & parallel dunes (p.18)
Spits and barriers (see p15 of report) 18 landform features incorporating mid-bay spits, spits and barrier in region. Spits and barriers are elongate accumulations of sand formed by waves, tides and winds. These landforms can be reworked by rising sea levels. These features are formed and grow in the predominant direction of longshore sediment flow caused by waves. Generally, spits are backed by estuarine or lacustrine systems with salt marshes and lagoons.
Lacustrine system Henderson Lagoon
Embayed beaches Regular geometric planforms in beaches formed in response to wave refraction.
Soft Estuarine Shores and Saltmarsh (p.21) Geomorphic types (a) Boobyalla, Little Forester. (b) Big, Musselroe, and Little Musselroe Lagoons, Scamander, Georges Bay. (d) Henderson Lagoon Application of a worldwide typology of geomorphic settings in which saltmarshes occur provides a good comparative benchmark of regional diversity.
Soft estuarine: Swash bars & delta
Coastal Dune Management - Natural Vegetation, Mobility and Reactivation Coastal dunes function as a buffer: protecting hinterland from storm surge frontal dunes act as a storage and transfer zone of beach sediment vegetation determines the stability of a sand dune. Acceleration of coastal erosion by humans Causes of blowouts off-road vehicles in dunes or mud-flats, alignment of access tracks to beach (pedestrian and vehicle) water run-off from hard surfaces, into estuarine systems Pollution, sediment inputs.
Major causes of dune erosion Wave erosion of foredunes leading to removal of vegetation. the destruction or modification of natural vegetation by fire. Human recreation and alteration of composition of native plant species. Grazing by introduced animals, such as, sheep, cattle, rabbits or native browsing animals in large numbers. Dieback of natural vegetation within the dune system due to Prolonged drought. Off-road vehicles in dunes or mud-flats, Alignment of access tracks to beach (pedestrian / vehicle).
Determining dune mobility status (p.40) Triggered by Tasmanian State Coastal Policy (1996) clause 1.4.2 Development on actively mobile landforms such as frontal dunes will not be permitted. Comparison of aerial photography 1949± to latest photo runs to acquire temporal and spatial components of coastal dunes. Short term hours through to months; Medium term several months to several decades. Planning timeframes - Australian and International Standards to be in the order of 50 to 100 years.
Dune mobility status current (p. 40/95) Character Current dune mobility status (Currmob (00-99) 00 Unclassified 10 100% vegetation cover (fixed dune) 11 70% - 100% vegetation cover (transitory) 12 50% - 70% vegetation cover (transitory) 20 30% - 50% vegetation cover (transitory) 21 10% - 30% vegetation cover (actively mobile dune) 22 <10% vegetation cover (actively mobile dune)
Dune mobility status Historic (p.40/95) Character Historic dune mobility status (Histmob) (00-99) 00 Unclassified 30 100% vegetation cover (fixed dune) 31 70% - 100% vegetation cover (transitory) 32 50% - 70% vegetation cover (transitory) 33 30% - 50% vegetation cover (transitory) 34 10% - 30% vegetation cover (actively mobile dune) 35 <10% vegetation cover (actively mobile dune)