The river is in full flow after a period of heavy rain.
The weir was sited here in the 1930s to allow the placement of a flow measuring device at a time when the valley was being considered as a site for a reservoir.
It comes to me as a great surprise that no pics yet of "The Surprise" as mentioned, here and here? (On a sunny day, please!). Halcyon days fondly remembered paddling in the Derwent at Grindleford.