Beach storm erosion
Some of the Shoalhaven City beaches have been affected by storm wave erosion in the past. A combination of analysis of aerial photography dating from the 1940s to the present, ground level photos or erosion scars and numerical models of coastal processes are used to understand and predict how storm waves will impact on beaches and dunes.

The models use wave data and statistics, tidal information, site specific bathymetric information, wind data and information about sediments to provide a consistent assessment of hazards at all beaches.

It is possible to delineate zones that would be directly affected by storm wave erosion for events of different magnitudes.

Zones that would be affected by consequent slumping of the dune face, or where foundation capacity would be reduced for different storm magnitudes can also be calculated, for the immediate time frame, and longer term (50 year and 100 year) planning horizons.

Coastal recession
The alignment of the coast may recede over longer time periods for several reasons, including:

1. A sediment budget imbalance (e.g. sand is being lost offshore, or into adjacent embayments or inland away from the beach. This inland transport has happened at Culburra Beach);
2. Estuary entrance instability - sand is moving into the tidal delta of the estuary or lake. Flood scour can also move sediment from estuary and lake entrances offshore. This happens at Shoalhaven Heads when it opens, causing recession around the surf club area;
3. Beach rotation - Longer term, or persistent changes in wave direction or wave height can cause the shape of a beach to rotate, as sand migrates from one end of the embayment to the other;
4. Climate change - Climate change scenarios for eastern Australia have been prepared by CSIRO (2001) and Australian Greenhouse Office (Pittock 2003), as well as the Intergovernmental Panel on Climate Change (IPCC 2001). Climate change may lead to sea level rise, changes to ocean currents and temperature, changes to wind and wave climate (strengths and heights), rainfall and runoff and air temperature, with consequent effects on ground water, coastal flooding, foreshore stability, entrance processes and coastal ecology.

The effects of these variables can be assessed using models to calculate the risks that sea level and other climate change scenarios pose to coastal development.

Coastal inundation
Storm waves and storm surge can overtop coastal dunes, causing flooding of low lying land behind the dunes. When the entrance of a coastal lake remains closed for extended periods, the lake level may rise to the point where low lying property or roads are inundated.

Dune instability and sand movement
Periods of storminess and strong winds combined with loss of vegetation on coastal dunes can initiate or increase the movement of wind blown sand from the beach and dunes into residential areas behind the dunes. This cause a nuisance for residents, but also depletes the supply of sand on the beach.

Geotechnical hazards - rock fall and landslides
The geology of some cliffs and bluffs makes them susceptible to undermining of resistant layers, causing rock falls. Other coastal bluffs may be affected by slumping, particularly in wet weather, due to weathering of rock layers. These processes are investigated through geological and geomorphic studies, studies of ground water flows, and studies of processes such as wave erosion of the base of the slope.