An experimental beach barrier could be key to rebuilding eroding coastlines
hakaimagazine.com
hakaimagazine.com
In Australia we've had a lot of permanent fix approaches which were massively counter-productive. If you want to stop sand being mobile then be prepared to lose it entirely. Really? about 200m-500m back from the waters edge is probably the limit of where routine construction should take place. it doesn't make for million dollar views but its safer for that property owner, the commons (assuming you live in an economy where the intertidal zone is public access) and the dunes.
The Gold Coast is a huge sweep of beach which depends on sand from the river Tweed, which was walled off to make a clear run for boats, and now they have to pump sand to replenish. Noosa depends on sand pumping. Rocks might help, they might even make some fantastic surf breaks but they wind up altering the nature of the beach. If you want a beach like surfers paradise or main beach or noosa, you really don't want rocks.
The berm he's made suits his local hydrology. It won't be exactly the same everywhere.
I kind-of hate being the typical HN naysayer. I'm not a tidal engineer or an ecologist or civil engineer. This is stuff which is discussed quite a lot in Australia, since we cling to the coast and an image of ourselves as "in love with the sea" it becomes increasingly necessary to look at how to hold on to what we've got. The run of sand up the eastern seaboard of Australia is amazing. (its like barchan dunes, permanently on the move, in our case south-to-north)
I've visited some of the beachfronts of Washington state and Oregon and they're glorious. Huge trees litter the tide line, amazing to see. We've nothing like that in Australia really, our rivers aren't full of giant redwood logs like that. We have different problems with disappearing Kelp forests, as does the Californian coastline, Oregon might have some of the problems Washington State does.
A nice example of that is https://en.wikipedia.org/wiki/Sand_engine:
“A volume of 21.5 million m3 of sand, dredged from 5-10 km offshore, covered an area of 128 ha, spanning 2.4 km along the coastline and extending up to 1 km offshore. The sand was deposited in the form of a hook-shaped peninsula. Wind, wave and tide action were allowed to distribute the sand further.”
Since it was successful, the same approach was used in the UK, too (https://coastalsolutions.ireport.royalhaskoningdhv.com/13001...)
FWIW: Half the human race lives less than 200km from the sea.
https://www.reddit.com/r/MapPorn/comments/uxrinu/half_of_the...
I'm 135km from the coast (I'm north west of Sydney, AU) but that's a 2h5m drive away. I'd not claim to be coastal.
200km means no one in the UK could be considered not coastal -- IIRC it's impossible to be more than ~115km from the coast.
I think a more telling statistic is that in Australia, more than 85 per cent of people live within 50 kilometres of the coast - mind, even 50km inland wouldn't fit what I would think of as coastal dwelling.
I appreciated the info in the GP comment and I realize Australia is likely more extreme than average, but one of the reasons humans are so concerned about rising seas and eroding beaches is because it impacts so many lives.
If 90 percent of people lived more than 200km from the coast and it was sort of "a handful of weirdos" that lived near the beach, I think humans wouldn't be so distressed by these things. It would be "Meh, nature out there can do what it wants. My house is safe and life goes on."
Anyway, I'm sure most of the population lives near water, mostly oceans, but sometimes (inland) along rivers. Proximity to the coast is very misleading, as obviously the risk is predominantly down to elevation.
As I noted, 100% of the UK live within 120km of the coast, and my weirdo assessment of their populationi aside, with an average elevation of 160 metres, most of the land will be fine. London's screwed, of course, with even only minor sea level rises. They're an exceptional case in all kinds of ways. Let's move on.
Best info I can find is an NPR article that suggests some research 15 years ago estimated about 600M people lived within 10 metres of sea level. So, if Greenland goes, they're all displaced.
Anyway, this doesn't really contest TFA's point, which seems to be 'large aggregate will slow down erosion'. Obviously holding your soil in place doesn't help much if it's held in place under 10 metres of saltwater.
I used to get all up in arms about "Why! Do people live There! When it keeps flooding???" Then I looked at the data etc.
We could stand to do a better job of working with the environment and building things more able to survive known issues for specific places. I'm always interested in clues to how we can do this better, but there is no place on Earth without some kind of natural disaster that routinely threatens the area.
It's a case of pick your poison.
Yes - viewed from your location, 200km definitely isn't.
But in the "from orbit" view - 200km away still has huge effects on the geology, climate, economy, etc. of a place. Or - ask someone who grew up in western Kansas, then joined the Navy.
I live 11km by car (9km on a map) from the excellent beaches here and almost never go because it's "too far".
We definitely are a costal nation. I love hearing the ocean roar as I go to sleep.
Note that all the projects mentioned are along the US Pacific coast. So I don't think you are being a naysayer, as much as pointing out that it is not useful everywhere.
I live on the east coast of Florida, and we have similar problems to Gold Coast with infrastructure blocking the longshore drift of sand. Sand is constantly in need of replenishment in locations say, south of Port Canaveral. I wonder if we will ever have a property right to the river of sand in the same way that water rights are enforced upon rivers. I seem to remember a method proposed of placing wave attenuators just past the break as a way of depositing sand, but unfortunately I cannot remember the name of it and could not find it through a quick search. I was hoping that we might try this method where I live.
My hometown beach was fixed by restoring connection to lagoon behind it and allowing the sand to be dumped in the ocean not the lagoon. Restoring the lagoon and digging a channel helped but what really helped was building new bridge that didn’t block the flow.
They used to dredge sand to have enough in summer. Now there is plenty in summer but can get rocky in winter after storm.
Examples:
- If the coast is too steep, the rocks won’t reach an equilibrium, and you now just have erosion of rock before your erosion of sand.
- If egg-laying sea/coastal life needs sand like sea turtles or some birds
- Surfers and tourism (as you mentioned)
- If the sand erosion is acting as a source for something downstream; stopping the sand movement will cause erosion in that area (nourishing the beach with sand would probably be a better fit)
(Edited formatting)
"The river with a city problem" is a good read about the insanity of building greater Brisbane on a giant floodplain.
Kiribati is already under. We get quite a lot about Oceania problems, displacement.
I think thwaites is still treated as the next generations problem.
A local measure that reduces wave energy creates a sediment trap, reducing or reversing local erosion.. However some where downstream from this site there is now less sediment coming in than is going out. So there it is going to erode now.
These type of measures usually end up pushing the problem downstream (a coastal system has a dominant sediment transport flow direction).
Actual solutions must look at an entire coastal system and usually involve continuous dredging, damn removal or lots of breakwaters, walls etc. This is all well known amd cam be modeled to a pretty good accuracy with software. However time amd time again a town solves their problem by pushing the erosion to their neighbours
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* there will still be seasonal variation based on summer/winter wave patterns and weather.
Those pictures are a few years old. Compare Google Earth.[2] They're a few years from losing the golf cart path. The hotel might have another 20-30 years.
[1] https://stolenhistory.net/threads/ritz-carlton-half-moon-bay...
[2] https://earth.google.com/web/@37.43372402,-122.4416652,22.97...
[1] https://www.slc.ca.gov/wp-content/uploads/2018/11/2017-Publi...
The Demon river article about the catastrophic floods in BC last year is well worth the (long) read. I've shared it with a number of friends: https://hakai.org/the-demon-river/
I am reminded of the two interpretations of the story of King Cnut and the tide[0]: the misconception that he tried to control the sea, and the actual story in which he was subordinate to it.
Sure, but they were losing 50 feet per year. It's reasonable to try to slow that down.
[1] https://www.rijkswaterstaat.nl/water/waterbeheer/bescherming...
And here's what's left today: https://goo.gl/maps/HXDdUSxcjXCpGeh26
I can maybe see it being reasonable if you purchased the house 50 years ago, when the sea was really fare away. What I don't get is why you by a house 5 meters from a cliff, when you know that the sea can eat 2 meters in a winter. Why should tax money go to secure your poor investment? These houses are essentially worthless, yet priced like it's a 30 year investment. Hilariously some of the owners have been forced to pay property tax on lots that a half way down the cliff or out in the sea.
In any case, this was worth the read. Its really counterintuitive that loose rocks don't just get swallowed into the ocean
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A group of residents in North Cove, Washington State, has developed a solution to the erosion of their coastline using piles of loose cobble. After dropping a load of rocks from the end of a road in 2016 to see what would happen, local farmer and drainage commissioner David Cottrell expanded the project to create a two-kilometer-long berm of rocks and stumps that shifts with the waves and collects sand, rebuilding the beach. The community's solution looks less like conventional structures such as sea walls and more like the dunes and berms that centuries of storms and tides build on their own, resembling the techniques many Indigenous communities use to cultivate shellfish.
As climate change progresses, coastal communities worldwide are searching for solutions to combat rising sea levels. Hard barriers like sea walls and riprap often cause further erosion and are expensive to build. By contrast, building beaches back could be enough to prevent some of the catastrophic land loss that many states in the US are forecasting due to climate change, according to coastal resilience experts.
North Cove's solution is influencing projects nearby and in California, Europe, and Guam, and is transforming the tools that agencies and communities can apply elsewhere. Engineers have long depended on rigid sea walls, and North Cove's berm is showing the benefits of a softer approach. The project has been successful in rebuilding the beach, and some species, including clam beds and shorebirds, have returned to the area.
It's really not that long and if you're genuinely interested you make an effort to read it. Not everything can be boiled simply down to a handful of sentences without losing key detail.