For inland waterways, KTA 2207 [23] assumes a flood runoff with an exceedance probability of 10~4/a. This flood runoff can be determined either purely on a basis of probabilities or by extrapolating from statistics available. KTA 2207 uses this extra­polation, which is based on the Kleeberg and Schumann method [44]. This extrapolates from a peak level water runoff with an exceedance probability of 10~2/a to a peak level water runoff with an exceedance probability of 10~4/a.

This flood runoff value obtained, finally, gives the design basis water level from a corresponding water level runoff relationship for the location concerned.