<p>Looks like something that the Severn has dumped on it's shore at some point.
</p>
Severn Bridge in the background.
<a rel="nofollow" class="external text" href="https://www.flickr.com/people/49392213@N00">David</a> from London, UK
CC BY-SA 2.0
<a rel="nofollow" class="external text" href="https://www.flickr.com/photos/rnddave/3322749441/">Dumped</a>