BEACH-DUNE MONITORING

I have had the pleasure of being associated with three coastal geomorphologists who have had a passion for monitoring profile change on Australian beaches. The first was Ian Eliot. He helped me establish 4 profile lines at the central part of the embayment north of the Moruya River on the NSW South Coast in late 1971. He was doing a PhD at ANU with an interest in rip current and beach morphology at Durras Beach. He later studied Warilla Beach with Des Clarke before moving to Perth where he has examined changes to Trig, Scarborough and other beaches.

The second was Andy Short, who started his beach studies at McMasters Beach before leaving Australia to study in the USA where I first met him in 1969. On his return, first at Macquarie then at Sydney University, Andy undertook the impressive, long-term monitoring of Narrabeen commencing in 1976. He was for many years associated with Don Wright in the Coastal Studies Unit and published many papers on the beach model that was stimulated by the work from CSU at different locations. Since “retiring”, he has his found another patch of beach to monitor south of the Moruya River while maintaining a fascinating life on beaches around the world. More on Andy another time!

Here I want to detail aspects of the work of a third colleague, Roger McLean. Rog and I teamed up in 1972 when we were on the staff of the now defunct Department of Biogeography and Geomorphology at Australian National University. As Research Fellows, we were free to pursue our coastal interests without the need to chase research grants—those were the days. As a relief from the bush capital, we raced down the coast every 2 weeks to capture the low spring tide. When absent on other projects, other staff of the Department undertook the measurements. There were numerous adventures during this period including mishaps with vehicles! But we continued the observations, either individually or separately, until I dropped out in the early 90s.

Once Rog took up his professorship at ADFA he was in a position to maintain the surveys along with a colleague, Jiashu Shen. Together they continue to monitor the original four profiles and some others on a regular basis. Photos are taken at the sites to capture changes in dunal form and vegetation. Jiashu has also been monitoring groundwater levels. The beach is now referred to as Bengello although papers published as far back as 1973 have called the profile site Moruya. The work has resulted in several publications and conference presentations and the data continues to be analysed by Rog and Jiashu.

I must pay tribute to all that have assisted the team over the years in profiling. They endured many difficult but otherwise enjoyable conditions. In the past, we attempted to profile as far seaward as we could safely stand. At times this meant swimming across the trough to the offshore bar with the survey pole. Rog has since had to abandon this method developing a technique for surveying alone. I am not sure that university OH&S requirements would accept this but, like Andy, he is “retired”. Thinking back I doubt whether what we did back in the 70s would be permitted today. Fortunately Ian Turner and colleagues at WRL are able to use sophisticated techniques to get results at places such as Narrabeen.

The time series of the profiles at Bengello has captured beach changes at a range of scales. We were fortunate in starting these surveys prior to the 1974 storms. The beach receded around 80m between 1974 and 1978 then commenced the recovery of the beachface and the foredune. Pat Hesp was also observing this recovery of foredunes in his PhD study north of Hawks Nest. Similar amounts of beach erosion volumes determined by Angus Gordon at other locations were found at this site.


Photo of a scarp was taken in 2007 after the Pasha Bulka storm; this event did not reach the 1978 position
Photo of the scarp with Rog perched on a ladder; this is the scarp of June 2016 still not back to the 1978 position

 

 

I am showing a photo of the erosion scarp in May 1974 featuring Jack McLean, Roger’s dad. Another photo of a scarp was taken in 2007 after the Pasha Bulka storm; this event did not reach the 1978 position. The third photo is of the scarp with Rog perched on a ladder; this is the scarp of June 2016 still not back to the 1978 position. The photos highlight not just the scale of cut into the foredune as well as the enthusiasm of Roger to get to the beach as soon as practical to do a survey.

So here we have three decades of scarping of foredunes following major storm events. It is in locations such as these, unimpeded by seawalls, that we can assess how much beaches can ambulate; the evidence from these surveys is that for sand- filled compartments like that north of the Moruya River, the beach will oscillate around a mean position as post-storm recovery brings the sand from offshore back to the beachface and then into growing foredunes. It takes time but as long as there is no long-term loss of sand from the compartment’s sediment budget the beach will recover. The question is for how long will such resilient behaviour continue both with sea level rising and perhaps increasing frequency of extreme storms.

Regular monitoring of beach and foredune change of the type undertaken by Roger, Ian and Andy has been driven by a love of the beach, by scientific curiosity, and by a preparedness to dedicate the necessary time and effort. It is individually driven with little or no research funding, or sustained institutional support. Yet the results have been tremendous; there are few records like these anywhere in the world. Now is the time for a new approach such as that being pioneered by Ian Turner and colleagues at WRL. But there must be an acceptance that such monitoring has value and must be sustained into the new climate era.


 

Words by Prof Bruce Thom. Please respect Bruce Thom’s thoughts and reference where appropriately: (c) ACS, 2016, posted 18th June 2016, for correspondence about this blog post please email admin@australiancoastalsociety.org.