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 2006, 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 and 2005, was again upgraded; it had already been digitised in the late nineties.
