Dr Rip (aka Rob Brander) presents his latest publication educating on the dynamic beach environment. From a solid scientific base he explains how beaches form, what drives waves and how rips develop. This book gives a simple, entertaining explanation of coastal processes, which will enrich your beach experience with understanding of the natural features. Chapters cover all ‘Essential’ aspects of the beach experience from the science of waves, beach types, safety and 'An idiots guide to driving on a beach'. Reading this book feels like you are having a conversation with Dr Rip, rather than reading a science text book.
The following is an excerpt from Dr Rip’s Essential Beach Book, talking about beach types and the importance of sea level for coastlines. Makes you think about wave setups that would have been present when the sea level was 150m lower than today when none of the beaches we know today would have existed...
This is a great intro to the science of the beach environment and will boost your appreciation with understanding. Scope it at the bookshop.
|Beaches: stuck between a rock and a hard place|
It’s easy to group beaches into categories on paper, but many beaches are mixtures of the ones described above. Regardless of the type of sediment found on a beach though, in order for a beach to form there has to be a lot of sediment around in the first place. Then there needs to be a place for these sediments to sit. In other words, they need to get stuck somewhere. Suddenly, the shape of the coastline becomes really important as all those little nooks and crannies and long straight stretches become potential resting places for large piles of sand. What controls the shape of the coast? Once again it’s all about the rocks. The shape of any coastline is really just a geologic imprint determined by the rock types that are there, which will have a range of different structures, hardness and shapes.
The variety of coastal geology around the world is incredible, not only between continents and countries, but even within the same region. Not surprisingly, the variety of beaches can be just as variable. If you don’t believe this, try driving around the beautiful coastline of the United Kingdom sometime. The range of beaches boggles the imagination and it’s mostly because of the varied geology. On the other hand, vast stretches of the Australian east coast share similar geological characteristics and beaches from Byron Bay all the way south to Eden, a distance of over a thousand kilometres, tend to look much the same. So it’s the rocks that provide the sediments and a resting place for them, but the story of beach formation is still not complete. The sediments still need to get to the beach somehow and that really depends on what the level of the sea is doing.
|On the left is Narrabeen Beach on Sydney’s Northern Beaches as it is today. On the right is what it could look like in fifty years if the sea level rises by a metre. Oh dear. Photos: Andrew Meares (left), Jojin Kang (right).|
|The importance of sea level|
With all the recent attention about global warming, you’d think that sea level rise is a bad thing. It may well be, but if it wasn’t for sea level rise, our beaches wouldn’t be where they are today. Once sand is delivered to the coast it is then brought to the beach, thanks to the work of waves, tides, currents and wind. However, exactly where these processes occur depends on the level of the sea at the time and, as described on page 18, sea level has been anything but stable for the last 2 million years. It’s been rising and falling like a yo-yo because of repeated periods of global warming and cooling.
It’s a simple concept. When the earth experiences an ice age, a lot of the water in the ocean turns into ice. With less water in the ocean, the sea level falls. When it’s warm, the ice melts, water flows back into the ocean and the sea level rises. There have been times when the sea level has been much higher than it is today. We know this because old beach and sand dune deposits can be found well inland at many places.
There have also been times when the sea level has been as much as 150 metres lower than it is today. Think about that for a second. None of the beaches we know today would have existed. Most of them would have been vegetated countryside, high and dry, and a long way from the coast! Land bridges between continents and islands were exposed and you could have walked between Papua New Guinea and Australia, or Siberia and Alaska, if you felt like it. Obviously a lot of people did, as that’s how humans are thought to have migrated around the world. Sea level also has an amazing control on the rivers of the world and it’s rivers that carry sand to lakes and oceans. When the sea level falls, the river is just left hanging and responds by eroding its channel so it can again flow happily into the same lakes and rivers. This causes a huge delivery of sediment to the coast, so the coastline and beaches will start to march seaward. On the other hand, when sea levels rise, rivers respond by clogging up and dumping a lot of the sediment they are carrying inland. Therefore, not as much reaches the coast, and everything starts to move relentlessly inland. What has this all got to do with the formation of our beaches today? After the last ice age 18 000 years ago, the sea level rose very rapidly as the earth warmed up and the ice melted. The coastline and all the sand that was lying around would have been bulldozed and flooded in a landward direction. When it was all over and the sea level stopped rising about 6500 years ago, the ocean had flooded many old deep valleys, creating estuaries, and filled up smaller valleys and coastal indentations with sand, creating beaches. In other words, many beaches simply got stuck between a rock and a hard place. What most of us don’t know is that compared to where the sea level has been over the last 2 million years, the present-day sea level and location of our beaches is unusual – we are living in a unique time.
Here today, gone tomorrow: the future of our beaches?
In geologic terms, 6500 years is not a long time and many coastlines are still trying to adjust to the last rapid rise in sea level. Unfortunately a lot of this adjustment involves erosion, but it is important to remember that erosion is a natural process. In recent years, there has been a huge increase in the public and media awareness of climate change, global warming, and sea level rise. This is a good thing because we should all be aware of the impacts that our activities and lifestyles can have on the planet.
However, even scientists can’t agree on what is going to happen to the sea level in the next hundred years. Most think it is certain to rise, but by how much, no one knows for sure. It could be 20 centimetres, 50 centimetres, 1 metre or as much as 6 metres. It’s a complex issue that is beyond the scope of this book. However, sea level rise and the erosion it may cause to our beaches is not the problem. The problem is that we have made poor choices in the past by building too close to the beach or in inappropriate coastal locations, like the house shown on the next page, without an adequate understanding of coastal processes. Hindsight is always 20/20 and it is hard to argue with decisions to live close to the coast, but it’s important that we learn from these mistakes for the future sustainability of our beaches.
Whether sea level rise is bad for beaches is a matter of perspective. Imagine looking down from a headland at a healthy beach and sand dune system that is completely undeveloped. Now assume that the sea level will rise by one metre over the next hundred years. If you were to return to the same headland a hundred years in the future, the beach and sand dunes would look exactly the same except that everything would have shifted landward. In other words, it won’t disappear, it will just move.
Now imagine a heavily urbanised beach where the sand dunes and area behind have been built over by houses and roads.
If the same sea level rise occurred, the beach would try to shift landward, but wouldn’t be able to. The development will block it and the beach will have nowhere to go. As shown in the simulation on page 33, not only will the beach disappear, the houses and development will take a beating. It should be pointed out that this simulation is close to a worst-case scenario and most of the world’s beaches are not heavily urbanised … just the ones we seem to love the most.
|Would you buy this house? It comes with open water views and a short life expectancy! A good example of bad coastal development near Rodanthe on the outer banks of North Carolina. |
|Will our beaches disappear? Maybe, but maybe not. Measurements have told us that the sea level has already risen by 20 centimetres in the last hundred years, yet our beaches are still here, although some are feeling the effects more than others. Sea level rise also doesn’t happen overnight, but occurs slowly over years, decades and centuries so we do have time to try and ‘fix’ the beaches…|
(excerpt from Dr Rip’s Essential Beach Book, pp28-33)