Translations:Versickerung und Retention/81/en

For the difference in the amount of rainwater accumulated on a sealed surface of a property, V_Rück in m³ (see Equation 20), between the minimum 30-year rain event and the 2-year dimensioning rain, proof of harmless flooding on the property must be provided. If an exceptional level of safety is required, the yearly occurance of the dimensioning rain is chosen as greater than 30 a. The harmless flooding can take place on the property, e.g. with curbs or troughs, or through other retention areas, like retention basins, if people, animals or material goods are not endangered, so long as the precipitation water is not discharged on other fields. The following flood verification for guidance is dependent on the local conditions and if necessary for parts of the drainage system (e.g. in the calming areas).