Geography of Sheffield (Totley Brook passes south of Totley and meets Old Hay Brook at Needham's Dyke). The Sheaf flows northwards to join the River Don near Blonk Street Bridge in the city centre. This lower section of the River Sheaf together with the River Don, between the present Blonk Street and Lady's Bridge, formed part of the perimeter of Sheffield Castle. Porter Brook's source is just inside the Peak District National Park, to the west of the city, at Clough Hollow, also near Ringinglow. From here it flows eastward to meet the Sheaf, at a point now located underneath Sheffield Midland Station.
Geography of Sheffield air pollution measurements for Sheffield (City Centre and Tinsley districts) as well as many other UK towns and cities. The European Commission's COST Action C11 (COST- European Cooperation in Science and Technology) cites, in its conclusions on "Case studies in Greenstructure Planning" involving 15 European countries:- " "Sheffield is fortunate to have one of the strongest green structures of any city in the UK. This green structure, which at its core is linked by watercourses, underlies the City. The effectiveness of the river system as the core of the green structure is supplemented by: the agricultural area, the moorland, the