Our municipality has approximately 191 kilometres of coastline. Natural coastal processes make some of this coastline vulnerable to being eroded away or flooded.
Although rocky foreshores protect much of our coastline, there are still many low-lying coastal areas are only protected by sand dunes. This makes them highly vulnerable to coastal erosion, coastal inundation and coastal flooding following heavy rain events.
What are we doing?
Protecting vulnerable coastlines from natural forces involves improving dune vegetation, directing or limiting access across dunes to stop trampling, adding sand to the beach or, under extreme circumstances, using hard engineering such as groynes and sea walls.
We have taken a leading role in responding to the risks of climate change on our coastline.
We maintain an annual aerial shoreline monitoring program, and have engaged scientists from consulting company Water Research Laboratory to apply complex climate modelling on a local scale to produce coastal maps showing shoreline locations at high risk within our municipality.
We address coastal erosion, coastal inundation and sea level rise in our planning documents and factored these into our planning decisions.
Coastal Management
Council endorsed the Clarence City Council Coastal Hazards Policy in January 2021. This sets up a framework to develop ‘local coastal management plans’ for areas that require a coordinated and long-term response to coastal risks and hazards.
Coastal Management Plans will be developed for vulnerable sites with input from community and stakeholders. We are currently working on plans for two key priority areas: Cremorne (Pipeclay Lagoon) and Roches Beach.
The coastal management plans will focus on pathways to adapt to hazards on the coast. These plans will complement council’s existing ‘Reserve Activity Plans’ that address broader coastal management such as managing the natural, cultural and recreational values of the reserve.
It is important to note that our Coastal Hazards Policy includes a decision hierarchy which states that, “engineering solutions will be a last resort and only considered where the public benefit outweighs costs and beneficiaries are willing and have the capacity to pay”.
Monitoring changes to Clarence Coastal Areas
Beach erosion and coastal changes are monitored closely by council officers, through local citizen science contributions (the Tasmanian Shoreline and Monitoring Project TASMARC) and by extensive annual aerial photogrammetric monitoring of Clarence shorelines.
Coast Snap
Clarence residents can turn their everyday photos into valuable coastal data with a CoastSnap location at Bellerive Beach.
CoastSnap is a global citizen science project that captures our changing coastlines. A monitoring point was installed at the western end of Bellerive Beach.
Vire more about the project on the CoastSnap website: www.coastsnap.com
Water quality
Local councils and the Derwent Estuary Program collect beach water samples from sites throughout the Derwent estuary each week from the start of December to the end of March.
Water samples are analysed for specific bacteria (enterococci) which indicate the presence of contaminants from a variety of sources. Each site is classified as having Good, Fair or Poor water quality in accordance with state and national guidelines, based upon a rolling 5 years of data.
Local councils and the Derwent Estuary Program collect beach water samples from sites throughout the Derwent estuary each week from the start of December to the end of March.
Water samples are analysed for specific bacteria (enterococci) which indicate the presence of contaminants from a variety of sources. Each site is classified as having Good, Fair or Poor water quality in accordance with state and national guidelines, based upon a rolling 5 years of data.
Beach monitoring reports
- Clarence Shoreline Monitoring Program Report 2021-2022
- Climate change impacts on Clarence Coastal area 2009
- Clarence Shoreline Monitoring Program Report 2021-22
- Coastal Hazards
- Winter 2011 Storm Events WRL Report
- Lauderdale and Roches Beach land ownership map
- Lauderdale environmental assets assessment of climate change on coastal and marine areas – 2012
- Powerpoint Summary – Photogrammetry 1948 -2020 and Aerial monitoring 2011-2020
- Roches and Cremorne Beaches – habitat mapping bathymetry and sediment analysis – dune nourishment
- Seastar Bambra Report
- Tasmanian Coastal Adaptation Pathways Project – Lauderdale Recommended Actions – 2012
- Technical reports for coastal engineers
For health and safety of all members of the public, swimming in the Derwent is not recommended for two days after heavy rain, and never in the vicinity of stormwater pipes or urban rivulets.
Red Tides
From time to time a phenomenon commonly known as a ‘red tide’ can occur in waterways and at beaches.
A ‘red tide’ is a marine environmental event, where tiny organisms, such as algae, go through an intense growth period (called an algal bloom), which can colour the waters red.
The red colouring comes from the algae and is a natural occurrence, not a pollutant.
You can read more about red tides on the Derwent Estuary Program website.
Lauderdale seaweed
In spring, seaweed can build up in Ralphs Bay near Lauderdale Primary School. This is because of an increase in nutrients in the water, an increase in sunlight and the right kind of southerly swells to push seaweeds in toward Lauderdale and above the high tide line. As it breaks down it can get rather smelly.
How does it happen?
Lauderdale looks out onto a sheltered basin of shallow water with occasional swells. In spring, there are lots of nutrients in the water that have yet to be soaked up, and at the same time you get a big increase in sunlight that promotes growth, including growth of seaweeds on the seabed as well as phytoplankton in the water column.
Much of the Ralphs Bay, and beyond further into the estuary, is shallow enough for light to reach the seabed and promote algal growth. This process can involve a variety of species, with a lot of red algae that in lower light levels. They grow on anything from reef to the small shell particles out on the sandy seabed. In the right kind of late spring swells, all the weeds that aren’t strongly anchored to something often end up piled on beaches. It is a natural process, but it is monitoring to see if such events increase as nutrient inputs to the region increase with increasing urbanisation and development of salmonid farms offshore etc.
The smell
The smell is made up of multiple contributors. The initial smell after deposition can be attributed to the high amounts of iodine in seaweed. However, the most unpleasant of the odours are produced by volatile sulphuric compounds, such as hydrogen sulphide and methyl mercaptan, as the material breaks down under anaerobic conditions. It is best to remember that the whole process of decay is doing good things for the coastal environment, as there are a number of invertebrates and other animals that rely on this process to survive.