Any moving vessel produces currents and waves in the surrounding water. The sheltered waters of some inlets, estuaries, rivers, lagoons and lakes have allowed the natural development of soft sediment shoals and banks. These may be eroded by boat wake and/or propeller jet. Some Tasmanian waterbodies are suffering unnatural and largely unnecessary erosion as a result of boating activities.
All boaters can help care for Tasmanian waterways by limiting their wake to a size appropriate to the area.
High
speed wave wake in open water.
Low wake from slow operation where erosion is likely to be a problem.
Known problem areas in Tasmania
No systematic assessment of the susceptibility of navigable Tasmanian waterways to vessel effects has been undertaken to date. The affected waterbodies that have been identified are generally otherwise little disturbed so erosion and other vessel effects are more readily apparent. Known problem areas (and management responses) include:
Within the World Heritage Area, motorised boating is only permitted on specified waterbodies - for details contact the local Parks and Wildlife ranger or see the Parks and Wildlife Service Tasmanian Wilderness World Heritage Area Management Plan.
Marine and Safety Tasmania (MAST) enforces a 5 knot speed limit in most port areas and has regulations limiting vessel speed to control damage to shores, facilities and other vessels.
Tasmania Marine and Safety (Motor Boats and Licenses) By-laws 1997, Section 28 states, amongst other things, that:
a person ... must not ... drive ... a motorboat ... at a speed exceeding 5 knots ... within 60 m of ... any shoreline, river bank, [etc].
Once initiated, the erosion caused by wave wake or other vessel effects may be very difficult to control.
Remediation works may be expensive or in themselves cause further habitat damage or loss of amenity. The trends towards increasing boat ownership, more powerful engines and rising sea-level all add to the potential for problems so there is a need for greater awareness of vessel effects on both natural values and other users of our waterways.
Guide to Low Wake Boating
To help boaters minimise the impact of their activities a Guide to Low Wake Boating (pdf) has recently been distributed to all registered Tasmanian boat owners.
If you have a comment to make, or know of another area where wave wake or other vessel effects may be causing erosion, please let us know.