Rias

This is the estuary of the River Colne, in Essex.

Given the size of the estuary you are perhaps thinking that the river itself is a sizeable torrent but…

…this is the Colne, just about a mile from where it becomes tidal.  So how come the tidal part of the Colne leaves such an impression on the landscape?

The answer is that the Colne is a ria.  A ria is a river valley that has been permanently flooded by the sea.  The sea level has risen allowing it to come inland along the river and spill over onto the flat valley floor on either side.  And it is not just the main valley that is flooded but also the lower tributaries too.

I left the main channel to follow Brightlingsea Creek and then turned off again to follow the smaller St Osyth Creek.

Both the tributary and its tributary were tidal and much, much wider than you would expect from their feeding rivers.

So the rivers formed the valleys and then the sea rose and flooded them.  Thus the sea was lower in the past and, as we saw last week, this is evidence for previously lower temperatures, with water locked up in ice rather than in the sea.

Subscribers check your inbox for some notes to help you spot other British rias.

2 thoughts on “Rias”

  1. We’ve just found you, and as we live by (and sail, canoe, kayak and windsurf on) the Colne we have enjoyed your post! We shall look forward to more, and thank you for creating this site.

    1. Hey, that’s great, Justine. It must get pretty busy in the summer with all of that going on. I took my photos the weekend before last, when all sensible people were keeping warm at home.

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