Expert Details
What will happen to our beaches with climate change? Ask “Dr Rip” about our changing coastlines.
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Name: Dr. Robert Brander |
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Description:
| Dr Rob Brander (aka Dr. Rip) is a coastal geomorphologist and Senior Lecturer in the School of Biological, Earth and Environmental Sciences at the University of New South Wales in Sydney. He has been studying beaches and surf zones for 20 years and completed a PhD on the morphodynamics of rip currents in 1997. Brander has published over 20 articles based on his research on rip currents, coral reef-islands, and the 2004 tsunami. Rob is a member of the Tamarama Beach SLSC and is passionate about his Science of the Surf (SOS) program. |
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| Questions and Answers |
Questions Posted by: Peter Brock |
| Qn: Hello there I have come across a web site that attempts to explain the differences between shell middens made by human activity and shell deposits (ie made by natural processes of wind and water). One of the differences they claim is that naturally occurring shell deposits have been sorted by wave and wind action which will arrange larger shells at the top and smaller shells at the bottom. I feel this goes against what I have observed on beaches with larger and heavier material dropping out of water first and the lighter material being carried further and ending up on the higher side of larger deposits. Over time I think the reverse would be true to what they claim - natural deposits would tend to have lighter material at the top and heavier material at the bottom. Can you please shed some light on this? The page is at http://www.aboriginalheritage.org/sites/identification.phpunder the heading "Shell middens". Ans: Hi Peter, You are right about the sorting of sediment on beaches. Generally heavier, denser sand grands settle out first with finer material being suspended longer and ending up deposited on top of larger grains. This is why after storms, you often see patches of black sand on the beach. The denser, heavy mineral black sands have winnowed their way down through the sand profile and are left exposed after the finer sands have been washed away. Natural shell deposits, or cheniers, are different. As the shells are composed of bioclastic material (primarily calcium carbonate), they have different densities and will behave differently in water. They also have a different shape to spherical sand grains and their hydraulic properties are also different. Cheniers are similar to beach ridges and berms on beaches in that they are consolidated deposits of sediment. In muddy estuarine environments, shells are left behind as lags with the finer sediment winnowed out and the action of waves and currents can push them together into one large deposit. Storms and large wave action can also deposit shells at the back of beaches with a tendency for the largest shells to be deposited last, or further up the beach. That's why you will often get the coarsest shells on top. |
Questions Posted by: Sharn Lucas |
| Qn: I've been to many coastal workshops where we are looking after very narrow stretches of beach. With predicted sea level rise and an increase in storm activity, is it a futile effort when big funds will probably only be injected for protecting the houses beyond the dunes? I've asked this question of a few coastal scientists, and they avoid answering it... I hope you wont too! Ans: Hi Sharn, I can see why coastal scientists avoid your question. Partly it's due to the fact that there is still a great deal of uncertainty about how climate change will impact our coasts. We don't know how much sea level will rise and if or how storm magnitude and frequency will change. I presume you are asking if it is futile trying to drum up future funding to save some sections of beach when most funding will be aimed at saving property? Well, it's certainly not a futile effort, we should be trying to protect all of our coastline as much as possible. However, and this is why you may not be getting answers, at the end of the day, when millions of dollars of property are in danger from an eroding and receding shoreline, that is where most funding dollars will be directed. There's just too much money and infrastructure involved to ignore a developed coast. Given that undeveloped coasts will maintain their character throughout climate change, it makes sense to focus our efforts on developed coastlines. However, with awareness of the environment and climate change increasing, I don't think it's futile at all to seek funding for protecting beaches. The government has just made a huge amount of money available for community groups under the Community Coastcare project (www.nrm.gov.au/funding/coastcare.html). So I think protecting the coast at all levels will continue to be supported. |
Questions Posted by: Peter M Miller |
| Qn: Hi Doctor Brander Storm events over the last few years have been washing right up to the sand dunes behind our local beach -Long Reef Sydney. Beach Spinifex in these dunes is stopping major erosion but we have noticed where there is Spinifex growing down over the beach - above the high tied mark, erosion is minimal.Do you know of any groups or councils planting Beach Spinifex along their beaches to save the sand dunes behind? We are interested in trying it if you think it is worth while - will get local council's approval if you do. Peter Miller Reefcare volunteers. Ans: Hi Peter, Even a little vegetation such as spinifex goes a long way to reducing and buffering the impacts of storm erosion. Spinifix roots are extremely effective at binding sand together and extend a fair way out laterally from the plant. So what you observed doesn't surprise me. Basically, following a major storm event where a foredune has been scarped, an incipient foredune will start to develop in front of the scarp quickly and will be colonised primarily by spinifex. The incipient can grow to 1-2 m in height presuming a long interval between storms. So the more incipients, the better protection for the foredune. There are many dunecare groups along the NSW coast who deal with dune revegetation and spinfex planting and I wouldn't be surprised if your Council has links to them. I was more familiar with the dunecare group working with Newcastle Council, but perhaps you could try getting in touch with the Coastal Environment Centre in North Narrabeen: www.pittwater.nsw.gov.au/environment/cec to find some local groups. |
Questions Posted by: Colin Samundsett |
| Qn: You leave me a bit mystified when you said natural beaches will adapt to sea level rise and move inland, - yet you were not all that worried; then said developed beaches and low-lying areas are going to have to face some major financial costs if sea level rises. How do Surfers Paradise, etc. slot in to your thoughts on this? Ans: Hi Colin, Yes, I guess that was a bit of a controversial statement, but what I wanted to point out is that natural beaches, i.e. ones without any development behind them, will shift inland if sea-level rises, but will maintain their profile as they do so. So if you were to take a picture of a pristine beach today, and then take the same picture in 100 years after a sea level rise of 0.5 m, everything would look exactly the same...just shifted inland a bit. So the point I wanted to make is that sea-level rise and climate change will not destroy beaches. Development is a different story. When we develop along a coastline we are effectively creating a solid boundary stopping beaches/dunes from migrating inland. So if sea-level rises on an urbanised coast, there's nowhere for the sand to go, but alongshore or offshore. Unfortunately there will be more interest in protecting the structures and property than there will be in preserving a beach. This will mean protective structures which will stabilise the shoreline, but will also contribute to the erosion of the beaches fronting them. In terms of Surfers Paradise, sea-level rise will be a massive problem. There are already significant erosion problems along the coast there after large storms and the development is almost like the wall of a fortress. The solution to sea-level rise in the case of Surfers, as will be for most other popular developed beaches, will be beach nourishment using sand from the continental shelf. This will allow us to maintain both the structures and beaches, but it will be phenomenally expensive and will be an ongoing process if sea-level rises continuously. |
Questions Posted by: Sibyl Payn |
| Qn: The dunes at the King's Beach end of Rose Bay in Bowen are very fragile at the moment...the sheoaks near the creek are being washed into the sea, and the sheoaks on the dunes in front of the road have their roots exposed and look sad .When people know little about a subject ,it is impossible to know the questions to ask. If you could list all the important things now known about dune presevation I could form an intelligent question. ie when I see well intentioned people walking across the top of the dunes spraying with roundup I sense this is wrong but do not have enough information to oppose it. I try to keep the bush between my house and the creek in a healthy condition but reall y don't know which plants not to touch. At the moment I pull out bullheads, barley weed (a burr)and a vine with a small dk.green leaf, which I found when I returned after 2 yrs had strangled all the bush gums.My question is ...is there some way you can educate us? Ans: Hi Sibyl, It sounds as if you've had some recent large waves or tides that have caused erosion and scarping of the dunes. If this is only a recent problem, the dunes should naturally build up again especially as there is a reasonable amount of sand in the area. However, this may take several months or more. The best thing to do to any dune to stabilise it is to vegetate it with the appropriate types of vegetation and to reduce the amount of human impacts (e.g. walking) on the dune revegetation. Dune vegetation is often site specific and I would suggest that you contact your local council. I would be very surprised if they did not have someone who deals with local community groups, or even coastcare groups, about sustaining local dunes. There is probably also an environment officer who deals with weeds and vegetation. So my advice would be to contact them as they probably know the system the best. It is also important to get the correct information about the local dune vegetation as it could be dangerous for individuals to tackle the problem themselves by removing or adding the wrong vegetation. |
Questions Posted by: Lee Thompson |
| Qn: Rob, There was recently an issue on the central coast (Merewther and Bar Beach near newcastle) where surfers were concerned that beach cleaning with tractors and dune revegetation by the council were destroying the surf break, which is a bit of an icon for the area. Can you explain how that might work? Is there a solution to keep both parties happy? Ans: I've been watching tractors on the beaches doing a lot of different things over the years. Mostly they are just used for beach cleaning, but I've seen them take sand that was building up at the back of the beach and push it into the water "to fill in the rip", which of course would never happen and actually help erode the beach temporarily! Fortunately I haven't seen that sort of activity in a while. The tracks and ruts left by beach cleaning itself will not have any impact on the beach (in terms of increasing erosion or deposition) and it certainly won't have any effect on a surf break. I'm fairly familiar with Bar Beach/Merewether, having lived there for 2 years, and know about the dune reveg you mention. I don't think the revegetation is likely having an impact on the surf breaks, but I know where the surfers are coming from. It's an Endless Summer scenario where in the first movie the surfers ran over natural dunes to find a perfect surfing break in South Africa. In the second movie, 25 years later, they run over the dunes to see a lot of condos and vegetation where the dunes used to be and the surf break wasn't so good! The idea is that we always assume that sand is deposited from the waves onto the beach and then the wind blows the sand onto the dunes. Well, the opposite works too. Offshore winds can blow significant sand from the dunes back into the surf and help create banks and bars. If you vegetate those dunes and stabilise them, you cut off that supply of sand from the dunes to the surf....and you can stuff up the break. However, Bar and Merewether have been developed for quite some time and the amount of sand in the dunes is fairly small. The sort of effect I just described only occurs with major dune fields. So I really doubt that the dune stabilisation is having any effect at all on the surf breaks. Maybe it has compared to 100 years ago, but certainly not in the last few decades. Any changes in the quality of the breaks are likely more related to changing sand transport patterns due to different wave patterns in La Nina vs El Nino phases. So the surfers are wrong in this case. Dune re-veg is a good thing and the job done by the dune care groups and Newcastle City Council is impressive. |
Questions Posted by: Melissa |
Qn:Hi Robert I have three questions for you. Firstly, In what ways could the general public, coastcare groups etc be making a real positive impact, in your field of work/expertise? Secondly, If you could change one thing tomorrow about the way our coastal systems and resources are currently managed, what would that be? And lastly, What are your major environmental concerns for our coastal and marine environments in the short and long term. Ans: That's a good question and a tough one too. I actually think that given the extent of our coastline, overall it is managed pretty well. There are definitely problem hotspots, but these are generally related to development pressures, land use conflicts, and poor coastal management decisions. I think the best thing for Coastcare groups to do is to keep pushing for the conservation of as much coastline as possible. I also think educating the public about how our coasts work is important for getting issues into the national psyche. I would love to see proper, process-based setback lines adopted along the coast which would restrict any future development in the future and allow for slow buy back of existing structures etc. which are inappropriate. I am not all that worried about climate change as most natural beaches will adapt to sea level rises and move inland, but will maintain their character and will not erode. The change in frequency of big storms worries me, but again, beaches can adapt. I think developed beaches and low-lying areas are going to have to face some major financial costs to keep infrastructure in place if sea-level rises substantially and the prospect of offshore sand mining for nourishment is a likely reality and an expensive one. In the short term, i am more concerned with the rising numbers of coastal drowning and injuries and the lack of understanding of most of the Australian public regarding how the coast works. Hope that helps and thanks for your question. |
