On pre-filling probability of flood control detention facilities

Flood control detention facilities are widely used for stormwater control in urban areas. Standard design procedures are in most cases based on the design storm approach: a single flood event at a time is considered, at the beginning of which the facility is assumed completely empty. The possibility of pre-filling from previous events is then neglected and underestimation of storage volume may occur. In this paper an analytical probabilistic approach to estimate the probability of pre-filling is presented and its effects, due to outflow rate and storage volume, are investigated. Two different strategies for the outlet control are analysed. Results are validated on a case study.