Probabilistic Analysis of the Retention Time in Stormwater Detention Facilities

AbstractStormwater detention facilities are often used in modern drainage systems to reduce the hydraulic load on existing sewers, due to the increase of impermeable surfaces and to the more frequent extreme rainfalls, consequence of climate changes. Although their design is mainly aimed to limit uncontrolled spills into receiving water bodies, storage capacity for water quality enhancement is often considered, mainly with the purpose of increasing the retention time. Standard analysis is usually based on empirical methods or on continuous simulations. This paper focuses on the probabilistic analysis of retention times aimed to provide guidance to engineers for the design of stormwater detention facilities. In particular, the influence on retention time of the possibility of water mixing from consecutive rainfall events, due to the pre-filling of the storage capacity from previous runoffs has been investigated. Derived expression has been tested by their application to a case study

Graph-theoretic approach and sound engineering principles for design of district metered areas

Copyright © 2014 American Society of Civil EngineersThe design of district metered areas (DMAs) in existing water distribution networks, especially in urban areas, involves a high number of decision variables, and the effects of implementing them in districts have to be evaluated in order not to affect the quality of the service to customers. A new methodology for designing a given number of districts in looped water distribution networks is proposed here. It is based on graph theory and takes into account some important DMA design criteria: the maximum and minimum size recommended for a district, the connectedness of each district to the water supply source, and the absence of links between the districts. Therefore, it allows the creation of DMAs that are independent from each other. A recursive bisection procedure has been applied to create districts, while an algorithm for graph traversal has been used to verify whether each district can be reached from the water source and connectivity between the nodes. The successful application of the proposed methodology to a case study has proven its effectiveness for district metered areas design in real urban water distribution networks

Probabilistic design of multi-use rainwater tanks

AbstractMany studies have revealed that traditional approaches in urban stormwater drainage may sometimes be insufficient to manage properly the unbalance of water cycle due to urbanization. In response to these increasing concerns, many cities have encouraged the applications of local disposal of rainwater. In particular multi-use rainwater tanks, combine the advantages of infiltration basins and tanks for rainwater use.This paper proposes a procedure for their design based on an analytical probabilistic approach. Finally, an application to a case study is presented