To Subgroup members 25th Sept 2021

I have had to make this page as the pictures were too big for the email

On the 18th September 2021 I took these pictures around mid day.

The tide was rising from a ‘high’ low tide.

Looking to the west we can see just how high it was compared to the rock islands. At the lowest tides the sea only reaches about the south three quarters of the large island and is below the end of the groyne.

Looking east we can see that the beach is quite good. There are two rock falls, the further one has been there a while and the toe has eroded, if you follow the top slope you can estimate how big it was at the start.

The beach has built up well

and shingle has moved into the mouth of the river as is typical with high beaches here.

It seems to me that one small island would probably be sufficient to hold the beach like this.

This would not cause rip currents and would not cost as much as a groyne, even with risk factored in, as the water is very shallow.

Looking at the pictures above I wondered if the far fall had helped the accumulations. It also helped me visualise what might happen with a groyne in a similar position.

If I remember correctly the groyne has to be detached from the cliff face to satisfy NE and the WHS. They wish to still have access to the cliff face. But what happens when tides race through that gap?

At the very least it is a health and safety hazard as it will create a very strong rip current. That rip current will surely erode the cliff, undercutting it at the base and possibly up to the height of the groyne? That will trigger a fall which will fill the gap, but how much of the land above is likely to come down? Is it permissible to trigger rock falls? If so could we just grade the slope back and leave the debris on the beach to form a higher beach?

Would a single rock island hold this newly created beach?

You can see the path the sediment from the fall is taking, it is heading west. The wind conditions at the time are not driving the waves that way as the wind is from the south.

Image from Ventusky.com for mid day 18th Sept 2021.

Comments?

Mary

   
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