A distinctive feature of the catchment is the marked variation in the topography and character of the landscape, which varies from the upland moorland headwaters of the Dark Peak, where the highest point of the catchment is the Kinder Scout plateau at ; through to the intensively farmed and drained flat fenland areas that exist alongside the lower tidal reaches, where ground levels can equal sea level. These lower reaches are protected from tidal flooding by a series of floodbanks and defences.