Advanced fire flow risk analysis using EPANET

Abstract

[EN] A water reticulation system is key infrastructure that enables hydraulic water services. It is therefore a critical component in providing the full level of water service to a city’s consumers. Extended water outages and below minimal pressure is a risk for the water network and especially for fire flows. GLS has developed and implemented a multi-threaded client-server software application based on the latest open-source EPANET 2.2 hydraulic analysis engine which now enables city-wide fire flow risk analyses on a property-by-property basis in reasonable time. Previously it has been virtually impossible to assess the risk on a city-wide basis, for each and every property, and to consider the improvement of such risk in the master plan (MP) of the water distribution system. Hence, the focus of the MP has been the provision of flows and pressures for the peak hour demand scenario in the network. Consequently, many township developments, densifications, and land use re-zonings require a separate and focussed specific fire risk analysis to ensure the existing system is capable of providing the requisite fire flow and pressure. If not, specific additional MP items related to the fire requirements of the specific property have to be investigated and considered for implementation. The fire flow risk analysis produces a GIS-based heat map displaying a Fire Risk Compliance Score (FRCS) of areas and properties where the current system is inadequate to deliver the fire flows and pressures. Such a heat map provides valuable information that can be used to improve and prioritise the MP and minimise future additional ad-hoc analyses for specific properties or developments. The fire flow risk analysis also allows the identification of pressure management zones where adjustments to the pressure regime are required in order to ensure requisite fire flows/pressures are achieved. Various methodologies based on Pressure Driven Analysis and Demand Driven Analysis have been evaluated and tested on models from South African cities. Great care has been take to optimise the multi-threaded communication of the application with the EPANET engine to streamline performance and support concurrent hydraulic analyses. In addition, a concept of automatically creating unique fire events to reduce the number of analyses, has been introduced for large models. This has resulted in smaller cities that can be analysed on modern PCs with few processor cores in a few minutes and large cities that can be analysed in reasonable time on high-core cloud-computing platforms. Visualisation in GIS-based software greatly helps to control the analyses and interpret results visually. Critical areas can be identified on a broader scale and allows for a rational approach to decide where to focus on network augmentation, or alternatively to provide on-site fire fighting capabilities.