As part of a strategy development for the restoration of floodplains and their improved connection to the respective rivers' current water levels, a major question involved is the definition of a reference for the regarded water sections. For this purpose, historical conditions frequently serve as reference, though the available information thereto unfortunately proves highly imprecise. The creation of a map showing potential vegetation structures would be a great help. Floodplain vegetation characteristics are mainly determined by flood duration. 

Experience shows that when applied to historical conditions or achievable objectives, some of the parameters required for calculation are missing. When developing the Salix231 factor for the classification of floodplains and their respective river or for the determination of river bed erosion as a result of anthropogenic impacts, a calculation mode arose that allows to set up a map of potential vegetation structures on the basis of the effective elevation and the actual or fictitious mean water level. The formula's application sphere relating to mean water ranges between -0.5 m and +3.00 m. The lower limit (-0.50 m) is based on mathematical calculations, the upper limit of 3.00 m corresponds to the calculated aridity threshold (no flood days). 

 F = – 70,559 * Ln (X + 0,50) + 88,711   

 The project will present both the derivation of the formula and its application possibilities. For the  Elbe river, the demonstration application rests on examples of current and historical conditions as well as on projections of possible climate changes  (KLIWAS project) .