Coastal Restoration Trust of New Zealand

Coastal Dune Ecosystem Reference Database

Coastal Hazard Assessment Koitiata and Castlecliff Beaches: Rangitikei & Wanganui Districts Technical Report

Jon Bell
Publisher / Organisation
Horizons Regional Council
inundation, coastal erosion, climate change, Castlecliff, Koitiata
The shorelines at Castlecliff and Koitiata have been assessed for coastal hazards. For each of the beaches a comprehensive CEHZ (Coastal Erosion Hazard Zone) and CIHZ (Coastal Inundation Hazard Zone) assessment was undertaken. It has been shown that there will be no increase in either Coastal Inundation or Erosion Risk to properties at Castlecliff over the 100 year planning timeframe considered under this investigation. The mapping of the hazard zones shows that the landward extent of these hazard zones is located within the dunes behind the beach at Castlecliff. The investigation has shown that over the 100 year planning timeframe a number of properties at Koitiata will be at risk from coastal erosion. However, this potential risk is driven by the migration of the mouth of the Turakina River. It is assumed that this risk could be managed through the use of river training works, such as groynes, to control the alignment of the river mouth, as is done at Waikawa. It has also been shown that there is an inundation risk to properties at the western, seaward, side of Koitiata. The number of properties subject to this risk will increase over the 100 year planning timeframe. This inundation is largely due to the effects of wave run-up and the depths of flooding will not be great. The potential inundation risk at Koitiata should be taken into account when making future planning and building consent decisions.