SAND is a metaphor for all sorts of things, and the reference is almost always to its impermanence.
Think of the biblical injunction against the foolish man who built his house on sand. “And the rain descended, and the floods came, and the winds blew, and beat upon that house; and it fell: and great was the fall of it.”
Coastal geomorphologist David Kennedy brought fresh insights into sand at a forum in Inverloch last night when he talked about the dynamics of coastal landforms and how they respond to storms, sediment and sea level.
Yes, he said, sand was the most transitory of materials, always in a state of flux, but also one of the most permanent in the sense that it absorbs the power of the waves and storms and is endlessly recycled to where it is most needed.
Ward councillor and deputy mayor Jordan Crugnale organised the forum in response to the mystery of Inverloch’s disappearing beach sand, which has perilously exposed a new lifesaving tower just months after it was completed.
So alarming has the beach change been in less than a year that some 80 concerned people crowded into Inverloch’s community hub on a cold winter’s night to hear what an expert made of the situation.
There is also the question of a new path planned for Inverloch’s Surf Parade. The council has put the project on hold to get an expert assessment of the coastline's geomorphology to ensure this section of coastline can cope with the built asset and that it will be intergenerational and value for money.
Dr Kennedy, an associate professor at Melbourne University, admitted upfront that he had no great knowledge of Inverloch’s beach dynamics, beyond a visit that afternoon, but put the matter into perspective by describing what happened on surf beaches in general, and a couple of much-studied beaches in particular.
He said every beach was a highly dynamic ecosystem in a permanent state of flux with massive movements of sand each day, influenced by storms, winds, tidal surges.
“It’s always talked about in terms of coastal erosion damage. What we’re actually seeing is just the sand moving somewhere else. In geomorphology terms we often look at it in terms of hazard and risk. Sand moves around but it’s only when it interacts with human systems that we have problems.”
The consequences are illustrated most dramatically by what happens when a sea wall is erected to protect houses and other infrastructure. Erosion doubles at either end of the structure and it won’t be long before the sea reclaims the wall and the land behind.
Left to its own devices, a sandy beach maintains itself pretty well, he said. “Sand moves and the shoreline moves. That’s natural. Beaches are an essential part of absorbing waves. The beach is always changing shape. Bars and rips move as the sand moves in relation to the waves.
“During storm surges, the beach profile flattens. Once the storm goes, the sand will move back onshore and the beach builds up. The dune system is a store of material for a storm event.”
Of course what everyone wants to know is whether the sand is going to come back to Inverloch beach. The answer, with all sorts of qualifications, is “Probably”.
In general, if humans don’t interfere, dunes will reform and beaches will restabilise, but it can take many years for this to happen.
Then there’s the problem of time: while we have aerial photographs going back to the 1950s, that’s the blink of an eye in geomorphological terms. The beaches operate on annual cycles but also operate on longer cycles over decades and centuries, and we simply don’t have enough data about our beaches to make confident predictions.
Of course we are facing new challenges: rising sea levels and rapid population growth, most of it near the coast, which means we’re entering uncharted territory for many beaches.
June 25, 2015
Thanks for the fascinating story on geomorphology and the nearby coastline. It's great to learn something quite new and gain insights into the really big picture of what goes on when ocean meets earth. It might be wise for coast dwelling communities like ours to acknowledge that there is something much, much bigger going on with sand and beaches, and that this eternal phenomenon dwarfs our immediate desire to walk and play by the sea.
Linda Gordon, Wonthaggi
June 25, 2015
Thanks for reporting on the meeting so effectively.
As a followup, I will draw your attention to the book A Coastal Retreat P.I.R.G., 1977 which details the historical coastal reserve utilisation process dating back to the turn of the last century with much written about Inverloch.
Ed Thexton, Inverloch
June 25, 2015
Professor David Kennedy’s presentation was excellent and has great relevance to the ongoing debate about expanding the Hastings Port precinct.
Most notable was his observation that wherever man interferes with coastal processes, via building too close to the water and thereby having to install sea walls, they inevitably either collapse or the immediately adjacent coastline generally suffers extreme erosion. This is especially true in areas with strong tides, such as Western Port
Local examples of this are the north end of the sea wall at Pier Road, Grantville, the collapsed sea wall near Malcolm Drive, Grantville, and the eastern end of the massive rock wall at San Remo. The end of the sea wall built at Portsea after the Port Phillip channel deepening is another example.
So if the planned expansion at Hastings ever went ahead, (five kilometres long and 500 metres out into the bay), what else could this ever be but a “massive sea wall” that would do untold damage to the Ramsar-protected coastline either side of it.
We can only hope that the warnings Mother Nature has given us via the above “scale models” will be heeded.
Kevin Chambers, The Gurdies