Wooli Beach Coastwatcher June 2012 – Subject: New Brighton Beach Scraping Trial
It is the intention of the author to post from time to time information, and comment related to the Dunal System. The opinions are those of the author, or his contributors, and do not reflect necessarily the “official” line of CCPA who graciously allow this column. With the imminent release of the “new” plan and our weekend meeting I feel it is timely to send my thoughts along to committee members at this juncture.
In January, 2012, the “New Brighton Beach Scraping Trial: Analysis of Dune and Beach Profile Data” was published by Rayner, Carley, and Coghlan of the Water Research Laboratory, School of Civil and Environmental Engineering, University of New South Wales. Contact person, Catherine Knight, Byron Shire Council (BSC), 70 Station Street, Mullumbimby, NSW, 2482. Hard copy of this report is already in the hands of several CCPA committee members.
This is an important document which was commissioned by the Byron Shire Council (BSC). Readers may or may not be aware I own a beachside property at New Brighton, in the Byron Shire, so these experiences and impressions are indeed first hand. In both areas there is neglect and misunderstanding of the dunal system at both an individual level and at a council level which has contributed to the bad state of the dune in both areas, particularly Wooli. Recent beach scraping at New Brighton is helping to re habilitate the dune. I review key points of this document, and add comment applicable to the Wooli situation.
The background to this report: resulting from severe storms in 2009 and 2010, there was significant loss of dune top (my personal estimate, some 4 metres) along the New Brighton Beach. My measurements at Wooli indicate a loss of about 7 metres also along the dune top at South Terrace. The BSC undertook beach scraping along a 1.7 km section of beach September-October, 2010. See photos (to follow). This activity appeared to be well conducted by the contractor, using at least three machines working in concert, and was accomplished over a week or so, with minimal dislocation to the recreational value of the beach. There is anecdotal information that some areas were deliberately skipped as the immediate beachfront property owners were identified as having a “Green” ideology, and complained to Byron Shire Council (BSC) that “their” dune was not to be touched (!) — anecdotal I am sure. Skip areas would detract from the whole exercise. The timing of the beach scraping at New Brighton would appear to have been correct when the beach was naturally built up; at Wool, locals will tell you that build up of the beach occurs towards Christmas..
Subsequent to this activitiy, there has been, in the eyes of the New Brighton beachgoer and property owner, substantial build up of the sand dune. It is noted, however, that no further measures have been undertaken at a Council level, but individual beachfront property owners have responded with plantings of natives including Spinifex grass, Pigface, and Native Morning Glory to assist in stabilization of the dune face, and encourage further aggregation of sand with natural trapping of wind blown sand (photo to follow). Where these supplementary activities have been undertaken, it would appear that a greater degree of sand retention has occured; it is acknowledged that the additional benefits of planting have not been studied in this document.
Beach scraping is a traditional practice along the New South Wales and Queensland coastline, with the aim of restoring sand to the dune, and increasing dune mass. It was widely undertaken following the cyclones in 1974. In fact, the New Brighton dune was actually built at that time…it is a man- made structure.
At first glance, reading the introduction, the document is a bit short on back ground history. Is the descriptor “Trial” correctly used? First paragraph, p 6 “feasibility” should perhaps read “impact”, and comment “unlikely to be sufficent to fully offset present and future coastal hazards” this is not the point of the study i.e. a conclusion that does not follow from the study data. The report says that “the scale of beach scraping is unlikely to sufficent to offset coastal hazards and/or future climate change”. We all accept that beach scraping in itself is not the solution, but should be viewed as part of a system of dune management. However, once these matters, which have an ideological flavour, are set aside, then the document’s research findings can be considered.
The method looks to me reasonable, but I query the need for the number of survey sample sites. The report does not note that between about location 41 and 42 there is a buried rock groyne which would inhibit north ward flow of sand. This groyne would appear to be successful in limiting northward flow of sand. Readers may be un aware the New South Wales legislation prohibits the building of “hard structures” in areas of coastal erosion, which is a pity as they have a part to play in the protection of coastal communities. The impact of beach access points is not really considered as these were not really stabilized in the exercise, and there is sand erosion occurring where people walk through.
Page 9, information was collected by “Council’s surveyors”. The Byron Shire Council (BSC) is not known to be impartial in it’s beliefs, and actions. Were the surveyors independently contracted?
There is an important point at the bottom of page 9 where it talks about small changes in the lower beach induce relatively large changes in the contour of the dune; consistent with the general understanding about the importance of dune toe reinforcement. Simply put, if the base of the dune erodes, the sand above will collapse down, to reform a natural angle of about 30 degrees (this can be seen in the well grassed healthy dunes south of the houses on South Terrace at Wooli).
Following beach scraping, the total effect was average seaward gain of some 5 m. Comment, although the dune top has not been reformed to its previous position a seaward gain at the base of the dune not only creates a significant buffer zone to protect houses, but also restores the natural dune contour thus the dune is more stable over time.
If I read the report correctly, the scraped sand is replaced over time by natural “longshore onshore sediment transport”, an important point. At Wooli, it is often possible to discern dissolved sand in the surf which is available to be deposited back onto the beach to replace sand moved shoreward by beach scraping. On page 28, there is a recommendation that future works should create a slightly higher and wider dune, which we all would agree with.
On page 17, it talks about wind effect, commenting that easterly winds help to bring in sand. This I think underscores the point that there are differences in beach sand ecosystems, and, although the general principles remain, no two are exactly the same. Locals at Wooli will tell you that the easterly wind brings direct wave action which actually erodes the beach, but that the winds and wave action from the north east help to deposit sand on the beach. This report makes no reference to trapping of wind blown sand which has not be undertaken at New Brighton. At Wooli, sand trapping (see previous column) is effective and is contributing to build up of a fore dune; with build up of sand on both the north and south sides of the sand fence. Item 3.3 reviews the impact of Wave Climate and notes that there was an overall lack of extreme events during the survey period. Recall back to 2009 and 2010 when extreme weather took at least ten feet off the top of the dune at New Brighton, and see their pictures page 27. I was there. Without going into detail on this point, the report seems to be acknowledging that the “extreme” events were the main factor in the large degree of dune loss, without actually postulating sea level rise, from climate change/global warming (etc.).
Comment and conclusions. Consider first, some basic economics. Are these measures “cost effective”? 1.3 km of beach was scaped, I believe at a contracting cost of $160,000.00 (information from the Byron newspaper “Echo”) which equate to $123,076.00 per km. From a political point of view, that fact that this was untaken by the BSC, a known supporter of the “Retreat” ideology for Coast Zone Management was quite significant. Even BSC is aware of the economic impact of protecting properties along the coast. Applying this cost to the dune side properties only, assuming there are 25 properties per km(average home frontage 40m), it is $4,850.00 per property; less if this amount is amortized over the general community. Land tax alone on these properties is $12,500 per year. If this event was undertaken once every five years, over this time some $62,500 in land tax would have been paid, so the government is well ahead on its investment. Beach scraping has resulted in the restoration of a protective dune leading to greater confidence in the property market, which in turn creates rates and land tax for government. I estimate there would be at least a 20 – fold multiplier to the value of coastal properties from this investment in dune rehabilitation, potentially adding 20 x $4,850.00 equals $97,000.00 on average to the value of New Brighton beach front properties. This is in contrast to Wooli, where in the last year their have been to my knowledge only three house sales, and at last count there were twelve properties with for sale signs up. Beach front values at Wooli are about one half of what they were pre 2009. The most recent sale of a partially completed house, for $680,000 is not far off land value, hence there is little added value along the Wooli Beach strip for DAs, and capital improvements. At Wooli, there is public land, including the school along the dune strip. As others have questioned, what would be the cost of relocating the school compared to basic measures to protect the dune?
CVC documents written, it would seem, to avoid to doing anything to protect Wooli, comment that “for environmental reasons beach scraping is no longer a viable option” (refer their “Wooli Beach Rehabilitation Plan”, 2005, page 4). This conclusion is quite spurious. Yes, there are “things” that live in the sand (but lucky for us not to the same extent as Frank Herbert’s sci fi classic “Dune”) which form part of the beach ecosystem and it is right to consider their role, and impact on them of beach scraping. But, at the end of the day, if there is no beach, there will be no where for them to live, anyway. The part II of this study, examines the effect of beach scraping on beach micro fauna, and will be reviewed in the next edition of the Wooli Coastwatcher.
In conclusion, the “New Brighton Beach Scraping Trial: Analysis of Dune and Beach Profile Data” is an important and timely study that demonstrates retention of dunal sand following beach scraping. The conclusions of this report support the application of beach scraping in coastal areas threatened by dune erosion. The report does not comment on further measures to preserve the dune. All are necessary as part of a coordinated response, to achieve the best results. The BSC is to be congratulated for its efforts, but also needs be reminded of the need for further measures, including sand trapping, and stabilization of sand mass with plantings. Our ability to re build dunes eroded by storm and tidal surge will allow protection of property in Coastal Hotspots, especially Wooli, for many future years.
Dr. Roger T. Welch
6/6/12.
