The alongshore sand distribution is very sensitive to the littoral drift, which strongly depends on wave direction. The shape of the cross-shore coastal profile is strongly influenced by wave run-up , with an important role for storm events with high waves and water levels. Great uncertainty still exists regarding predictions for local changes in wind regime and wave climate caused by climate change. The sea level will rise globally as a consequence of global warming, but regional differences are considerable.
This holds in particular for relative sea-level rise, i. Some coasts experience uplift especially in previously glaciated regions while others are subject to subsidence. Uplift can always be considered "natural", whereas subsidence often has an important human-induced component groundwater, oil, gas extraction. According to the so-called " Bruun rule ", an increasing relative sea level will cause a shoreline setback, which is approximately equal to the sea level rise divided by the average slope of the active coastal profile, when considering equilibrium profiles.
Consider, for example, a sea level rise of 0. The setback caused by such a sea level rise will be 50 m. Littoral coasts consisting of fine sediments will be exposed to higher setbacks than coasts consisting of coarser sediments. Log in. Page Discussion. Read View source View history. Jump to: navigation , search. Shoreline management guidelines. Sediment exchange between the sub-aqueous and sub-aerial coastal zones. Proceedings of the International Conference on Coastal Engineering 1 Article reviewed by.
Job Dronkers See the discussion page. Categories : Articles by Mangor, Karsten Reviewed articles Coastal protection Physical coastal and marine processes Beaches Sediment Climate change, impacts and adaptation Sea level rise. This page was last edited on 21 August , at Privacy policy About Coastal Wiki Disclaimers. Tidal inlets and river mouths are often by nature shallow and variable in location, which makes them unsuitable for navigation.
In order to improve navigation conditions and, to some extent, flushing conditions, many tidal inlets and river inlets have regulated mouths.
The regulation may consist of jetties, possibly combined with maintenance dredging programmes. If the tidal inlets and the river mouths are located on littoral drift shorelines, they are often in a natural equilibrium with respect to bypassing of the littoral drift, which normally occurs on a shallow bar across the inlet.
For the above reasons, regulated inlets are normally obstructions to the littoral transport which means upstream sand accumulation along the upstream jetty, loss of sand due to sedimentation in the deepened channel and the associated maintenance dredging.
All in all, regulated inlets will very often cause lee side erosion problems. Legislation requiring mitigation measures, such as artificial sand bypass, is not always respected.
At many such locations mitigation measures have never been introduced or severely delayed. In conclusion, past and present regulations of tidal inlets and river mouths are responsible for major erosion along many coastlines throughout the world. See also Typical examples of structural erosion and Port breakwaters and coastal erosion. Detached breakwaters are used as shore and coast protection measures.
In general terms, a detached breakwater is a coast-parallel structure located inside or close to the surf-zone. As this subject is too extensive for this page, see Detached breakwaters for a detailed discussion on the subject. Other types of coastal protection that do not protrude into the sea will, however, also cause increased coastal erosion. Seawalls and revetments are typically constructed along coastal sections to provide protection of the coast.
Seawalls are alongshore structures built as vertical walls, as sea dikes with smooth sloping stone revetments, as geotubes or as rip-rap concrete blocks or rock.
Coasts protected by seawalls are called 'armoured coasts'. The impact of seawalls on coastal erosion depends, among other things, on the location of the structure in the coastal profile, on the littoral drift and on the natural beach evolution [4].
In the case of a naturally accreting coast, the main reason for building a seawall is to protect coastal settlements from storm surge damage or to protect low-lying hinterland from flooding. The seawall is usually fronted by a wide beach and its impact on beach dynamics is negligible. Seawalls are built most often on eroding coasts; their primary function is to stop erosion.
However, the erosion process seaward of the structure continues and may even be enhanced. After some time no beach will be left in front of the seawall. At that stage the toe of the seawall will be scoured by waves and the structure will collapse if the toe is not sufficiently protected [5] Fig.
Whether a seawall enhances erosion before the beach has disappeared so-called 'active erosion' is site dependent. Active erosion increases with decreasing beach width. Three processes play a role:. The erosion of soft cliffs often appears to be very drastic, which is why they have, in many cases, been the first to be protected in an area.
However, before their protection they were the main suppliers of sediments to the littoral cell in question. Consequently, their protection leads to increased erosion at adjacent lower sections of the coastline. The result is that the erosion has been shifted to less resistant areas resulting in higher area losses per year.
Another impact of seawalls is the reduction of aeolian transport for the formation and extension of a coastal dune belt [12]. Other relevant articles on this topic are Seawall , Revetments and Seawalls and revetments. Decrease of fluvial sand supply to the coastal zone is a common cause of coastal erosion. Reduction of fluvial sand supply can result from different human interventions:.
Thousands of dams have been constructed on rivers worldwide, creating reservoirs which retain a large part of the sediment discharge from the catchment areas Fig.
The cost of beach rehabilitation can be estimated from:. NSW Government. Western Australia Government, USGS, News and information on El Nino. We have already upgraded the design of the site and we will be working to update the content over the coming months. Unfortunately many pages may not be where they used to be because this is such a major upgrade.
Skip to content. Geological background Beach deposits predominantly consist of sand particles that can be easily eroded by waves. Natural cycles of erosion and accretion Sandy beaches are dynamic sedimentary systems that naturally experience phases of erosion and accretion that operate over a range of time intervals 3.
Human activities that accelerate beach erosion 1. Coastal development The main pressures on beaches and dunes are urbanisation and developments associated with coastal tourism 7. Climate change related to global warming An increase in the frequency of major coastal storms or a rise in relative sea level can accelerate shoreline erosion and also trigger the erosion of dunes immediately behind the beach.
Example output from the stability line maps 3. Removal of dune vegetation The loss of protective vegetation is a major trigger for dune erosion. Relevant indicators Changes in the following parameters may indicate that a beach is being eroded or is at risk for erosion : a reduction in beach and dune areas measured by remote sensing techniques ; a reduction in protective vegetation on dunes 9 ; The cost of beach rehabilitation can be estimated from: the number and dollar costs of beach nourishment programs 9 ; and the number and and dollar costs of stabilisation works e.
More information NSW Government. J, Ferland, M. Wave dominated coasts. In: Carter, R. Behaviour of beach profiles during accretion and erosion dominated periods. What is coastal erosion? Coastal erosion can be either a: rapid-onset hazard occurs very quickly, a period of days to weeks slow-onset hazard occurring over many years, or decades to centuries. What causes coastal erosion? Where does coastal erosion occur in Australia? Single storm events have caused coastal erosion, such as that associated with East Coast Low storms in and that damaged beachfront properties in Sydney.
A series of large storm events in led to even more extensive damage to coastal properties and infrastructure in this region. Slow onset: The Twelve Apostles along the Great Ocean Road are a result of landscape change and coastal erosion over millenia.
There were originally 12 limestone features with 8 now remaining. These structures remain vulnerable to further erosion from waves. Around the Australian coast, nearly 39 buildings are located within one hundred metres of 'soft' shorelines and are at risk from accelerated erosion due to sea-level rise and changing climate conditions as at What is Geoscience Australia's role in reducing risk to Australians from coastal erosion?
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