So where was I this morning? In a 13th century document “Cartularium Priory de Gyseburne” this shallow boggy valley was referred to as Rivelingdale which sounds to me a place of Middle Earth but nothing like the idyllic Elven paradise Tolkien of Rivendell. Somewhere in the marshes below is quite a stream, deep enough to get you very wet if you choose a bad place to cross. It rises from a spring mentioned in the same document as Rotandekelde or Rutandekelde meaning red spring. I guess this may be describing the orange mud associated the iron salts at chalybeate springs.
No spoilers. The photo is geolocated so the answer is there if you know how to extract the info.