The sewerage network maps of the BWB provided the primary base to ascertain the type of drainage as well as the various catchment areas of rainwater drainage. With the aid of the current digital drainage network maps from 2004, the map “Management of Rainwater and Waste Water”, developed as part of the Environmental Atlas as early as 1992 and already upgraded once in 2003, was again upgraded; it had already been digitised in the late nineties. The map “Attachment 1: Periods of Waste Water Facility Development in Inhabited Areas (October 2001)” of the Waste Water Disposal Plan, with its schematic drawings of areas connected to the sewerage network after 1990, was also used. Detailed information was obtained from the BWB for certain specific areas.
