Seawall Repairs FAQ — Port Stephens

There is no set rate. Small repairs, such as repointing open joints or resetting a few displaced rocks or blocks, are priced on how many metres are affected and how hard the wall is to reach. Rebuilding a failed section costs considerably more per metre, with the total driven by wall height, material (rock revetment, concrete panel or interlocking block) and access for machinery. Approvals are part of the picture too: NSW DPIRD Fisheries says any works in the Port Stephens–Great Lakes Marine Park that damage or interfere with habitat need a marine parks permit. An engineer's assessment gives something firm to quote against.

Find out before any work starts. Port Stephens Council's 2024 Coastal Management Program says most of its study area, from Fern Bay to Yacaaba Headland and including the Port Stephens estuary, lies within the Port Stephens–Great Lakes Marine Park. The only exception it names is the coast south of Birubi Point. NSW DPIRD Fisheries' permit rules for the park say any works that damage or interfere with habitat need a marine parks permit, and they list seawall construction by name. Development in or next to the park is also assessed under marine estate and planning law. Ask your engineer and the tradesperson which approvals your repair needs.

Many failures start behind or beneath the wall, not in front of it. Wave action and tidal flow wash out the material that supports it, a process called backfill scour, until the face slumps, bulges or drops, usually during a big swell or storm surge. Port Stephens Council's 2024 Coastal Management Program, drawing on earlier studies, gives local examples at Sandy Point and Conroy Park in Corlette. In two precincts, wave overtopping has scoured the land behind the revetment and caused it to fail, with slumping in some sections. Near Conroy Park, erosion has caused severe undermining behind the geobag revetment. The CMP also lists part of the Swan Bay seawall as failing and needing toe protection.

Port Stephens Council's 2024 Coastal Management Program links it to the flood tide delta moving into the port, which has amplified the refraction of incoming north-east swell. Sand moves east to west along this foreshore at about 1,750 cubic metres a year. The CMP says the fragmented approach of protecting individual properties does not give adequate protection from wave action to all homes and public assets. It proposes investigating and designing revetment works in three precincts, including a new continuous revetment, and notes works in two of them would require removal of all unauthorised access ways and boat ramps. If stairs or a ramp cut through your wall, raise it with the tradesperson early.

Port Stephens Council's 2024 Coastal Management Program describes Shoal Bay as a 2.5 km sandy shoreline from Nelson Head to Tomaree Head, where sand moves mainly westward, around 10,000 cubic metres a year by a 2011 BMT estimate. With limited sand supply, its central to eastern part is gradually eroding, and the ongoing deficit is undermining stairs and accessways. A 2021 BMT assessment rated the shoreline next to a section of Shoal Bay Road at moderate erosion risk with limited potential for recovery. A falling beach leaves less cover over a structure's footings, so mention any beach lowering you've noticed when you enquire.

Treat a lean, a bulge or a sinkhole behind the wall as urgent. It likely means backfill has already washed out, and a wall in that state can fail suddenly rather than gradually, often in the next big swell or storm. Fence the area off and keep people and vehicles back from the top. Sandbagging a scour hole or repointing a few open joints can buy time, but it doesn't stop the backfill loss, so treat it as a stopgap while an engineer looks at the wall. If the wall is inside the marine park, check whether the stopgap itself needs a marine parks permit before you place anything on the foreshore.