Jetty Repairs FAQ — Batemans Bay

It depends on what the job changes. Swapping a rotten pile or re-decking on the existing frame is a smaller change than extending the jetty, adding a pontoon or building new. Where the jetty sits matters too. NSW DPIRD's marine protected areas mapping puts the tidal Clyde River inside Batemans Marine Park, mostly in the Batemans Bay Habitat Protection Zone, with a Special Purpose Zone over part of the lower river at Batemans Bay. Pelican Inlet, Waterfall Creek and the Buckenbowra River are sanctuary zones, and so is Cullendulla Creek, just north of the river mouth. Sanctuary zones are the most restrictive zoning in the park, so a jetty in or beside one is a different proposition from one on the main channel. Before any work starts we check which zone the jetty sits in and what Eurobodalla Shire Council requires for that location, and we plan the job around both.

Piles first: how many need replacing, how long they are and what they are driven into. A pile going into soft silt has to go deeper than one in firm sand or clay, and a long pile in a scour-prone stretch is more work to set. Then the timber above water: whether the bearers, joists and bracing are sound enough to keep so only the decking is replaced, or whether the frame has to come off and be rebuilt. Access is next. A jetty we can reach from the bank with a ute and trailer is a simpler job than one where everything comes in by barge. On the Clyde, work at the waterline has to fit around a mean tidal range of about a metre, going by Manly Hydraulics Laboratory figures, so tide times shape how the job is scheduled and how many low tides it takes. If a flood has scoured the bed around the pile bases, repairing that adds to the job, and on the upper river the bank at the landing may need work too.

The NSW Government's estuary profile gives the Clyde a catchment of 1,722.9 square kilometres draining through an estuary of 17.5 square kilometres, so a big flood sends a lot of water past the jetties. Floodwater can scour away the bed around pile bases, and floating debris can strike bracing and decking. For erosion-prone banks upstream of Nelligen, the Batemans Bay and Clyde River Estuary Processes Study, quoted by NSW Maritime, says floods and natural meander are far more significant causes of bank erosion than boat wash. After a flood, have the piles, the bed around them and the bank at the landing checked.

Close to a metre at Batemans Bay and a little more at Nelligen. Manly Hydraulics Laboratory's NSW Tidal Planes Analysis 2001 to 2020, published in April 2023, gives a mean tidal range of 0.915 m at Princess Jetty in Batemans Bay, with highest astronomical tide about 1.06 m AHD, and 1.024 m at Nelligen, with highest astronomical tide about 1.11 m AHD. AHD is the Australian Height Datum, the national reference level that sits close to mean sea level, so 1.11 m AHD means the highest tide reaches about 1.11 m above that level. Mean tidal range is the usual gap between low and high water. So about a metre of each pile is wetted and dried with every tide, which is the band where rot and borers get in, and we check the piles over that full height. H6 is the treated-timber hazard class for sea water, and turpentine is known for its natural resistance to marine borers.

Not according to NSW DPIRD's estuarine macrophyte mapping, which draws on imagery from 2012 to 2022. It shows about 145 hectares of Zostera seagrass and about 699 hectares of mangrove in the Clyde River estuary, and no Posidonia australis. Posidonia is mapped only in Batemans Bay itself, at about 21 hectares. The Commonwealth's endangered Posidonia australis meadows community runs from Wallis Lake to Port Hacking and leaves out the Batemans Shelf bioregion. If seagrass or mangroves grow near your jetty, say so when you enquire.

Read the policy before assuming either way. Some home policies include private jetties and pontoons and others leave them out, and flood and storm cover can differ within the same policy. Look in the Product Disclosure Statement for terms such as waterfront structures, wharves or jetties, and speak to your insurer before repairs start if you intend to claim. Photos of the damage taken before anything is moved, and a written breakdown of the repair from the tradesperson who quotes, are worth keeping for the claim.