Flood protection measures may be divided in "reactive" and "preventive" kinds of measures. Reactive measures, for instance, are constructions of reservoirs. Preventive measures serve to reduce the runoff "at the source" by infiltration and on-site retention. There is a significant potential of runoff mitigation in urban areas and arable lands as well. In urban areas application of the so-called "Swale-Infiltration Trench-System", replacing conventional sewer systems, can contribute to a mitigation effect. In arable lands surface runoff can be significantly reduced by application of the so-called "Compost-method", replacing the conventional kind of ploughing. A significant effect of these measures on extreme floods can only be achieved if they are widely applied in a certain catchment. A real problem is to motivate the decision maker to apply these alternative methods. Motivation depends ― firstly ― on the costs of the measures in comparison with their financial benefits and ― only secondarily ― on the so-called ecological awareness. In Germany, at any rate, these financial benefits can be proved concerning both urban areas and arable lands.
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