Innovative Approach to Fire Flow Assessment for the Christchurch Water Supply Rezoning

The Christchurch Water Supply Rezoning project involves changing zone boundaries and pressures for many of the large water supply zones of the Christchurch water supply. The Christchurch earthquakes highlighted the vulnerability of large water supply zones. Changes to the water supply zones offer an opportunity to improve resilience of the system, as well as extend asset life through pressure management and reduce operating expenses.

A key part of the project was assessing the effect of the changes on fire flow compliance. Assessing fire flow requirements and available fire flow for an entire city in detail would be prohibitively expensive, so a number of innovative approaches were developed to simplify the assessment processes. The processes included ways of using the available GIS data from Christchurch City Council to estimate the required fire flow for each land parcel in the city, and to assess the likely capacity of multiple hydrants in the vicinity of each land parcel.

The processes developed provide a practical approach to carrying out a fire flow compliance assessment across a whole zone or city in order to identify locations where further investigation to resolve deficiencies could be carried out. This approach could be applied to most water supplies across New Zealand where assessing fire flow compliance is important.