The part of the valley near the village of Ulpha is marked as "Dunnerdale" on Ordnance Survey maps, and upstream towards the village of Seathwaite is Hall Dunnerdale.
He wrote in The Southern Fells, "I ought to mention that I am aware that the Duddon Valley is also properly known as Dunnerdale, a name I haven't used in the book, preferring the former; just as I never refer to Blencathra by its better-known modern name of Saddleback.
[1] The "Dunnerdale Fells" are between Broughton Mills and the main Duddon Valley.
From the top of the valley, steep motor roads lead west over the Hardknott Pass to Eskdale and east over the Wrynose Pass to the Langdale valleys.
A less steep pass to Eskdale over Birker Fell leaves the valley at Ulpha, with extensive views of the Scafell range.