Surf Life Saving Queensland Magazine HOW ARE BEACHES CREATED? Beaches are dynamic coastal landforms that are created through a combination of geological, oceanographic, and ecological processes over extended periods of time. The formation of beaches typically involves the following steps: Source of Sand: The primary component of beaches is sand, which is often sourced from a variety of geological processes. This can include the erosion of coastal cliffs, weathering of rocks and minerals, and the breakdown of coral reefs and shells. Transportation of Sand: Once sand is generated, it is transported by various natural forces to the shoreline. This transportation can occur through rivers, streams, and coastal currents. Waves and tides also play a crucial role in moving sand along the coastline. Deposition: As sand is transported by water, it eventually reaches the shoreline. Here, factors such as wave energy, tidal movements, and sediment size determine where the sand is deposited. Calm waters typically result in the deposition of sand, forming beaches along the coastline. Shaping by Coastal Processes: Once deposited, beaches are continually shaped and reshaped by coastal processes. Wave action, currents, and wind all contribute to the redistribution of sand along the shoreline. These processes create the characteristic features of beaches, such as berms, dunes, and sandbars. Vegetation Growth: In some cases, vegetation such as dune grasses and shrubs take root in the sand. These plants help stabilize the beach by trapping sand and reducing erosion caused by wind and water. Over time, vegetation can contribute to the formation of dunes, which provide further protection to the coastline. Human Influence: Human activities, such as coastal development, engineering projects, and sand mining, can also impact the formation and evolution of beaches. Alterations to natural coastal processes can lead to erosion or gathering of sand, affecting the size and shape of beaches. IMPACTS OF SAND MOVEMENT ON QUEENSLAND BEACHES While the movement of sand is a natural and essential process for shaping our Queensland beaches, it can also pose significant challenges and risks to their stability and safety. The relentless action of waves, currents, and storms can lead to the erosion of sandy beaches. When sand is constantly stripped away from the coastline, it diminishes the width and volume of the beach,
increasing the likelihood of coastal erosion. This erosion not only threatens the integrity of beachfront properties but also compromises the safety of beachgoers and infrastructure. On the flip side, excessive deposition of sand can result in accretion, where beaches become overly wide and steep. While this may seem harmless, overly steep beaches can lead to stronger and more dangerous shorebreak waves, increasing the risk of accidents and spinal and general injuries for swimmers and surfers. Natural processes such as longshore drift can result in the formation of sandbars offshore. While sandbars are a common feature of many surf breaks, they can also create hazardous conditions for beachgoers. Waves breaking over sandbars can generate powerful rip currents, which pose a significant risk to swimmers by pulling them offshore. River mouths and estuaries are dynamic environments where sand and sediment are constantly in flux. Changes in river flow, sediment transport, and coastal processes can cause channels to migrate, altering the shape and configuration of beaches. These changes can impact navigation, recreational activities, and the stability of nearby infrastructure. AN EXPERT’S VIEW We spoke to Dr Julian O’Grady, a climate scientist researching coastal impacts at CSIRO. Julian has spent a career understanding how our shoreline changes, the effects on climate change on the movement of sediment (sand) and working to understand the negative effects on our beaches. “The natural coastline of Queensland is highly dynamic, constantly changing due to the movement of sand and sediment. For much of the coast the dominant movement of sand is northward. As the drift of sand move up the coast it encounter headlands and river mouths, causing a buildup of sand in some places and a deficit elsewhere, resulting in a range of beach conditions, from widening beaches to erosion- prone areas, the coast is in a perpetual state of flux.” While we may take sand as an ever-present in our lives, Julian explains that sand movement can provide good (and bad) benefits for our beaches. “Sand movement plays a vital role in shaping our coastal environment. It’s a natural process that replenishes beaches, creates diverse habitats, and maintains coastal ecosystems. However, when there is reduced sediment supply to the beaches we can encounter a few issues.” “Coastal councils are constantly investing in measures to mitigate the impacts of sand movement and erosion. From dredging and beach nourishment projects to the construction of seawalls and groins, these efforts aim to stabilise beaches and protect coastal assets from the dynamic forces of nature. Did you know the Gold Coast is actually one of the most controlled coastlines in Australia, there are a number of actions put into place to preserve the beaches.”
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