Physical Factors that Shape the Coast
The main physical factors that shape Tasmanian coastal, estuarine and marine environments are:
Ocean Beach, West Coast
(Land Information Services)
- winds (primarily westerlies from the Southern Ocean)
- wave and swell heights (these are related to wind strength and direction)
- nutrient level
- water temperature and salinity
- geology, geomorphology and substrate (the surface on which a plant or animal lives)
- duration and intensity of sunlight
- water clarity.
Physical processes play an important role in ecological systems. For example, light availability is a major controlling factor in marine primary production, so processes such as wave action and turbulence, which affect water clarity, will help dictate ecological structures. Ecological systems created by the physical processes listed above include:
Plankton from the Derwent River
(Gustaaf Hallegraeff)
- coastal zone terrestrial vegetation
- coastal dune fields
- estuarine salt marshes
- brackish-water communities
- intertidal communities on rocky and sandy shores
- attached species living in the sunlit zone
- plankton
- bottom feeders
- deep-sea communities.
Emergent and Submergent Coastlines
The Derwent River is an example
of a drowned river valley
(Christine Coughanowr)
Emergent coasts develop if an area of the coastline has been recently uplifted by tectonic activity or as a result of a recent decline in sea level. Some areas of the Tasmanian coast are clearly emergent because rising land or falling sea level expose wave cut cliffs and platforms above sea level. In contrast other areas of the coastal zone show distinctive signs of submergence.
Submergent coasts may be thought of as drowned landscapes, and due to this they are often highly irregular because the sea typically floods the lower reaches of river valleys. The ridges separating the valleys, however, remain above sea level and project into the sea as headlands. These drowned river mouths, otherwise known as estuaries, characterise certain areas of the Tasmanian coastline.
Tasmania's Coastline
The coastline of Tasmania is primarily due to geological processes over the ages, and therefore characterised by a number of different coastline types.
Tasmania's coastline consists of:
- headlands interspersed with sand beaches and lagoons in the north-east
- cliffed coasts, sheltered bays and drowned river valleys in the south-east
- cliffed coasts and sand beaches in the south
- sand beaches, headlands, river estuaries and harbours in the west
- open coast and river estuaries with numerous harbours in the north.
The coastal zone is often perceived to be a stable and constant environment, and the physical processes operating in the area are thought to be continuous and predictable, causing relatively little change. However, this is not true as the coastal zone is a dynamic place that can change rapidly in response to natural processes.
The background “noise” of this natural variation can be a hindrance to effective coastal resource management. For example, coastal users may wish to modify the coastal zone and construct a public jetty. Structures built on the foreshore such as jetties and groynes require an understanding of the physical processes at work in the coastal zone. Such knowledge enables the effects of various forms of human interference to be predicted and offset, or allowed for, in coastal development and works.
Contact: Coastal and Marine Branch
Coastal and Marine Branch
6th Floor, Lands Building, 134 Macquarie Street
GPO Box 1751
Hobart TAS 7001
Phone: 03 6233 3963
Fax: 03 6233 6800
Email: Coastal.Enquiries@environment.tas.gov.au
