A framework for evaluating the persistence of urban drainage risk management systems

Despite remarkable advances in urban flood management techniques, pluvial flood damages still occur throughout the world. This may be attributed to uncertainties in the rainfall events which may disrupt the normal performance of an urban drainage system and eventually lead to inundations and damages. Therefore, the conventional urban drainage management approach focusing on system security should be modified. As a new approach to urban drainage management, this paper defines the persistence of a system as the ability of a disturbed system to resist, buffer the effects of variable disturbances and return to accepted level of performance after disturbances and introduces a framework to evaluate the concept of risk management persistence for urban drainage systems based on joint consideration of resilience and resistance standpoints. Based on this perspective, some of the required indicators were selected from the literature and adapted to the present study in order to quantify urban drainage risk management (UDRM) systems persistence against disturbances. Evaluation of urban drainage measures would indicate the level of persistence achieved. As a case study, part of the urban drainage system of city of Tehran–Iran was analyzed using the proposed scheme. Four urban drainage measures including three best management practices (BMPs) and a conventional system were added to the current urban drainage system to assess the performance of various measures in improvement of the persistence of UDRM systems. Results indicate that the analysis of the systems persistence can efficiently enable urban planners to select measures with an insight into the behavior of the UDRM systems faced with disturbances.