Articles | Volume 17, issue 12
Research article
01 Dec 2017
Research article |  | 01 Dec 2017

Flood impacts on a water distribution network

Chiara Arrighi, Fabio Tarani, Enrico Vicario, and Fabio Castelli

Abstract. Floods cause damage to people, buildings and infrastructures. Water distribution systems are particularly exposed, since water treatment plants are often located next to the rivers. Failure of the system leads to both direct losses, for instance damage to equipment and pipework contamination, and indirect impact, since it may lead to service disruption and thus affect populations far from the event through the functional dependencies of the network. In this work, we present an analysis of direct and indirect damages on a drinking water supply system, considering the hazard of riverine flooding as well as the exposure and vulnerability of active system components. The method is based on interweaving, through a semi-automated GIS procedure, a flood model and an EPANET-based pipe network model with a pressure-driven demand approach, which is needed when modelling water distribution networks in highly off-design conditions. Impact measures are defined and estimated so as to quantify service outage and potential pipe contamination. The method is applied to the water supply system of the city of Florence, Italy, serving approximately 380 000 inhabitants. The evaluation of flood impact on the water distribution network is carried out for different events with assigned recurrence intervals. Vulnerable elements exposed to the flood are identified and analysed in order to estimate their residual functionality and to simulate failure scenarios. Results show that in the worst failure scenario (no residual functionality of the lifting station and a 500-year flood), 420 km of pipework would require disinfection with an estimated cost of EUR 21 million, which is about 0.5 % of the direct flood losses evaluated for buildings and contents. Moreover, if flood impacts on the water distribution network are considered, the population affected by the flood is up to 3 times the population directly flooded.

Short summary
Floods cause damage to people, buildings and infrastructures. Due to their usual location near rivers, water utilities are particularly exposed; in case of flood, the inundation of the facility can damage equipment and cause power outages. Such impact lead to costly repairs and disruption of service affecting indirectly people outside the inundated area. In this work a method to estimate the impact of floods on a water distribution system is introduced and applied to a case study.
Final-revised paper