Author(s): Terry Van Kalken; Antoinette Taylor; Matthew Davis; Nick Brown; Chris Bacon
Keywords: Flood hazard mapping; 2D modelling; LiDAR
Abstract: With recent flood events, continuing development of rural and urban land and increased awareness of climate change, the need for identifying regions of high flood risk is becoming more important. High development areas include the Auckland region and the hinterland of Christchurch in the South Island. Detailed flood assessments are undertaken on a priority basis where past events have highlighted an existing risk. However without the benefit of past experience it is often difficult to identify those areas at greatest risk from flooding. Rapid Flood Hazard Mapping (RFHM) offers a systematic and consistent conservative methodology to assist in the mapping of flood risk areas. The methods utilize high resolution topographical data derived from LiDAR, combined with 2D hydrodynamic modelling. Different RFHM methods have been developed for New Zealand applications depending on the required end use of the flood maps, which range from high resolution maps to identify individual properties at risk in urban areas to coarser scale products used for strategic planning and civil defence purposes. The paper describes the methodologies that have been developed and illustrates the application of these to case studies in the Auckland Region, North Shore City and Waimakariri District. The benefits seen from the end user perspective are also discussed, these in terms of the speed, cost and consistency of the applied methodologies.