Its source is on the eastern slopes of Mill Hill, three miles south east of Glossop and just north of Kinder Scout.

The flow of the Alport is partially diverted by a weir to feed into the Ashop above the impound weir built in the 1920s to increase the catchment area of the Derwent Reservoir prior to the building of the Ladybower Reservoir downstream.

The concrete structure of the weir is visible when travelling up the Snake Pass route from Sheffield.

The river is quite narrow and relatively shallow, making the rocky bed hazardous for kayakers who capsize.

By far the most challenging part is in the higher-volume upper section of the river, where a small tributary of the Ashop flows swiftly through a steep tunnel under the road.