Are artificial reefs a win-win- solution for coastal erosion on parts of the Bryon Coast?

 

EchoNetDaily, 22 July 2021:

A 2016 investigation into strategies to control coastal erosion commissioned by Byron Shire Council (BSC), recommended as the most economically viable option the construction, in the most vulnerable areas, of an engineered seawall with public walkway. There was the potential addition, at a later stage, of beach nourishment with sand sourced from elsewhere and the construction of groynes.

High tides caused significant erosion of the dunes at Clarkes Beach in Byron Bay. Photo Rosie Lee.

The building of seawalls has been the subject of a controversial court case brought against BSC in recent years. These seawalls were constructed privately in the Belongil area, although with the notable absence of a public walkway.

The report also identifies the majority of these walls as not designed to contemporary engineering standards.

Manfred Street beach after the 2016 storm. Public submissions for five rock wall DAs close on April 20. Photo Paul Spooner

Armoured coastline

Seawalls constitute what are known as an ‘armoured coastline’ and while they are common features in coastal areas around the world, they typically result in the eventual loss of all semblance of a beach in front of them. In addition they defer erosion to adjacent areas; which in the case of the Belongil seawalls is the northern part of the Belongil Spit, already subject to the most intense erosion in the area. The seawalls themselves also undergo severe erosion and require continuous and costly maintenance.

Artifical reefs with salients. Photo supplied

Artificial reefs

There is an alternative strategy that does not appear to have been taken into consideration by BSC. Artificial offshore reefs have the potential not only to protect vulnerable beaches, but to actively promote beach enlargement and growth through sand accretion.

One such reef was constructed offshore off the Narrowneck Spit near Surfers Paradise in 1999, and a second reached completion off the coast of Palm Beach in October 2019.

Constructed with a variety of human-made materials such as geotextile sand containers and concrete or quarried stone, artificial reefs can protect the shoreline though the twin principles of wave refraction and wave diffraction.

Read the full article here.