The River Horner, also known as Horner Water, rises near Luccombe on Exmoor, Somerset, and flows past Porlock into Porlock Bay near Hurlstone Point on the Bristol Channel.

[3] When the river level is very high, flood water builds up behind the ridge, causing it to breach.

[4] Evidence that the river was previously diverted to power iron workings has been found.

The remains of an iron hammer mill and 55m long, breached, embankment dam were excavated alongside the river in 1996.

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