TO STOPBANK OR NOT TO STOPBANK? A CASE STUDY

Peter Christensen (Storm Environmental), Helen Beaumont (Christchurch City Council – CCC), Martin Densham (CCC), Kevin McDonnell (CCC)

Abstract

When floods occur there are often calls to ‘fix’ the problem. Flood ‘protection’ works are often seen to provide just that – ‘protection’ – when in reality they reduce the risk or frequency or severity, but do not ‘protect’ or ‘fix’. Stopbanks are often seen as a fix for flooding but they are not appropriate in all cases and can have significant drawbacks. When the residents along the Ōpāwaho / Heathcote River flooded again in July 2017, a significant package of flood management measures was put together to reduce the risk of flooding. Stopbanks were considered as one of the options, but further investigation into their feasibility and suitability of them was recommended first. The question was, to stopbank or not to stopbank? At the end of the investigation Christchurch City Council (CCC) staff recommended ‘not to stopbank’, and this abstract outlines how the decision to allow room for the river was reached.