Beach Erosion

Gold Coast Beaches – A shifting story Photos ABC, News Ltd During 1925, the opening of the Jubilee Bridge made the Gold Coast’s beaches accessible to motorists from Brisbane and triggered a wave of development. Gold Coast Beaches have had periods of severe beach erosion ever since. Some of this is natural, and other events are due to man’s interference with (or impatience with) natural sand movement. On the Gold Coast sand particles predominantly come from the south east. Wind and currents are transporting sand from NSW and slowly moving it north to replenish the Gold Coast’s iconic tourist beaches. The Gold Coast sand source is the Clarence River in New South Wales, from which it travels to its sink, which is South Passage in Moreton Bay. This process is called longshore drift and the net rate of movement is estimated at 500,000m3 per year. Construction of walls and breakwaters interrupt this flow. One example is the old groyne at Kirra where sand built up on the southern side of the groyne as longshore drift was interrupted. Then there was erosion on the northern side of the groyne where the boulder wall was exposed. In 1967, a series of eleven cyclones removed most of the sand from Gold Coast beaches. This would naturally replenish very slowly, but tourism and property values were threatened in the meantime. Engineers from Delft University outlined a series of works for Gold Coast Beaches. Work on the Gold Coast seawall was standardised after the Deflt Report and it was designed to withstand 24 attack from a 1:100 cyclone wave. It is 16m across and 6m high. The Council built the urban sections. Non-Urban sections have to be added by private landowners prior to building or improving a house, at a cost of over $3000 per metre. Tourists walk over it every day without realising that it’s primarily a storm barrier, not a footpath. For many years, sand has been dredged from a variety of points along the city’s coastline to nourish the Gold Coast’s ailing beaches. These locations include the Broadwater, Tallebudgera Creek, Currumbin Creek, The Tweed River, and offshore. Training walls were introduced at the Gold Coast Seaway in 1986 to stop the Nerang River migrating northward. Other training walls have been constructed at the Tweed River, Currumbin and Tallebudgera creeks to help stabilise these entrances. The Delft report also recommended the construction of a sand bypass system to pump sand from the mainland under the navigation channel to South Stradbroke Island. This overcomes another barrier to natural sand movement caused by the entrance to the Broadwater at Southport. A sand bypassing system also commenced operating at the Tweed River in 2001. To stabilise the foreshore at Narrowneck, the Council has constructed an artificial reef 1/3 of the way between Burleigh Heads and the Gold Coast Seaway. So far the reef has worked well as a coastal control point, but has been disappointing in its secondary objective to improve surfing. A surprising benefit of the Narrowneck Reef has been its ability to attract marine growth and reef fish and is now a popular diving and fishing location. A new reef is also proposed for Kurrawa Park. In 2004 Gold Coast City Council proposed a new artificial reef for 21st Avenue Palm Beach. The proposed scheme included 3 reefs and beach nourishment. Some in the community didn’t like the idea and organised a “no reef” protest campaign that prevented the scheme being implemented. To give some idea of costs, the Tweed Heads bypass project costs were $5 million annually. The council spends between $2.5 million and $3 million just to partly replenish sand stocks every year. After 2012 storms it was estimated the beaches needed 10 million cubic metres of sand at an estimated cost of $80M, but there was no money and no place that could be used as a source for that much sand. After 2013 storms the Council wanted $30 million for a project principally covering only the Kirra Groyne and to move 40,000 cubic metres of sand to replenish 2 beaches. Some of the work the Council has done is not to restore natural flows, but preserve the benefits from unnatural flows. The Queensland Government constructed the Kirra Point Groyne in 1972 to trap sand at Coolangatta Beach. Surf conditions peaked in the 1970s, 1980s and 1990s during the decades of erosion experienced along the southern Gold Coast beaches caused by the unnaturally low sand supply to the region and the construction of Kirra Point and Miles Street groynes. Board riders from around the world travelled to Kirra to experience the popular (but unnatural) north-facing break. 25 The Tweed River Entrance Sand Bypassing Project was established in 1994 to open a navigable entrance to the Tweed River, and to maintain sand supply to the southern gold coast beaches. The first 10 years of operation were largely a success, but the shortening of the Kirra Point Groyne by 30m in 1996, resulted in Kirra Reef being buried in sand, also affecting the surf break. The bypass pumping now matches a natural rate of sand movement, but that doesn’t maintain the surf break. Under public pressure, recently the Council went ahead with the restoration of the groyne even though it interferes with sand flow. Everyone wanted to experiment in surf site engineering and had a very firm opinion. The EPA documents try hard not to reveal the strain the debate caused, “What to do with Kirra Point Groyne remains a significant and emotive issue, with some people advocating extending the existing groyne to its original length, while others believe that if should be removed or shortened further”. According to a report by the Griffith Centre for Coastal Management restoring the Kirra Point Groyne to its original length may have immediate benefit to surf quality, BUT this may soon disappear as more sand is trapped and the beach widens at Coolangatta. Another report— Kirra Point Groyne Effects Study— concluded that extending the Kirra Point Groyne would result in a wider beach at Coolangatta. This may also result in sand covering more of Kirra Reef. A year or more after construction, and $1.5M later, surfers are still divided over whether or not it has improved the break. It has supplied the Gold Coast with a site for a new helipad to service rich tourists, meaning that it will never be removed now, even if it makes matters worse. Before we get too hard on surfers for wanting to tinker with natural processes, an alternative idea mooted at one stage was to build a marina there, even more of a longshore drift obstacle. This perhaps hints at the real issue with maintaining a natural shoreline on the Gold Coast. The seabed and foreshore land is worth big dollars and attracts huge commercial and recreational interest. Some changes to accommodate new commercial and recreational infrastructure for a growing city is probably unavoidable. We have already made (and will continue to make) a host of decisions to develop the coastline in an environmentally unsustainable way. The cost of protecting all this vulnerable development is hidden at the time of construction, but is now falling on everyone. While I am no longshore drift expert, it seems like we have learned nothing, and keep making the same ill advised decisions. The Kirra groyne works needed to be a scientific investigation, amateurs needed to stay out of it. As for a marina, are you kidding! Dr Strauss, a local scientist, has said of urban beaches, “The beach would be able to withstand storms and heavy seas if it had a nice healthy dune system like at The Spit but we’ve got development right on top of the dunes and it just doesn’t have the ability to give and take”. We are now locked into an indefinite program of expensive works in order to maintain this status quo. The cost of the failure to sustain healthy natural dunes and unobstructed beachfronts now falls on the Council and the ratepayers. The Council is never likely to have enough money to completely paper over the flaws in these old decisions, sand (or the lack of it) will continue to be a Gold Coast obsession for many decades to come.