RiCOM - Coastal Canterbury Inundation

This case utilises the RiCOM model in conjunction with others to model near shore wave behaviour including inundation as a result of distal source tsunamis. Coastal Canterbury is the focus in this study with a South American wave source.

This case utilises the RiCOM model in conjunction with others to model near shore wave behaviour including inundation as a result of distal source tsunamis. Coastal Canterbury is the focus in this study with a South American wave source.

The 2013 tsunami review indicated that some eastern New Zealand coastlines have in the past, and will potentially experience significant tsunamis from distant sources in the future. It was estimated in the 2013 tsunami review, that along the Canterbury coastline the 2500 year return period at the 84 percentile confidence interval (1 standard deviation above mean) wave height for a distant-source tsunami (likely originating in South Peru/ North Chile) was 12.63 m. In response to this figure this case study set out to model the possible inundation that could occur in several coastal areas on the east coast of the south island including; Kaikoura and surrounds, Pegasus Bay, Christchurch and Banks Peninsula & South Canterbury. 

The RiCOM model was used in conjunction with several others during this study but was a key component of the near-field inundation modelling. It is initially run with a quiescent sea state set in accordance with local tidal heights which is coupled with far afield source modelling (modelled using Gerris) that is applied at boundary points of the study grid area. Accuracy of the simulated inundation is largely reliant on both topographic and bathymetric data of the study area with LiDAR and high resolution LINZ hydrographic data being used for some areas of this study but for the most part a lower resolution data set being used.

The RiCOM model provided projections of Wave height, Flow speed and levels of inundation for south eastern coastal areas of New Zealand.

 RiCOM christchurch wave height output

Wave height for coastal Christchurch area

 

It should be noted however that in order for the modelling to be as accurate as possible input data including topographic and bathymetric data needed to be both available and in as high resolution as possible. The study notes that while there are inherent uncertainties in numerical modelling such as RiCOM it is believed that this model has provided a best estimate of coastal inundation in Canterbury to date.

The scenario modelled in this report represented an extreme end member tsunami for the Canterbury coastline with a 2500 year return period. This makes it an appropriate reference point for evacuation planning and emergency management and while not intended for use in land use planning given the timescales of the scenario it can be used to highlight areas of higher vulnerability where a higher level of planning and consideration may be required.            

RiCOM christchurch inundation output

Inundation depths for Christchurch area

Associated Models

River and Coastal Model (RiCom)

The River and Coastal Ocean Model (RiCOM) is a numerical hydrodynamic model used to demonstrate near shore hydrologic conditions primarily surrounding water velocity and height.

References

Lane, E. et. al. (2014): Updated inundation modelling in Canterbury from a South American tsunami. NIWA Client Report No: CHC2014-100. Prepared for Environment Canterbury Environment Canterbury report number R14/78