Modelling the effect of sea level rise on tropical cyclone storm surge impact

Across Northern Australia Tropical Cyclones (TC) present a major hazard for coastal communities. Improvements to building codes and investments in disaster planning have had demonstrable impact on the resilience of exposed communities however the hazard to life posed by Storm Tide inundation remains a major concern. Projected sea level rise due to climate change over the course of this century suggests that the impact of Storm Tide events will be more significant in the future as higher sea levels expose a wider area to inundation. While knowledge of climate change impacts on the frequency and intensity of Tropical Cyclones has implications for storm tide impacts Climate Change damage assessments frequently assume the relationship between storm tide impacts and sea level rise to be linear. During Tropical Cyclone events, Storm Tide continues to increase in height in relatively shallow waters. This suggests that the nature of the relationship between sea level rise and Storm Tide impact may not be linear which has significant implications for climate change damage assessments and subsequent adaptation strategies proposed. To examine the effect of sea level rise on Storm Tide impacts this paper presents the results of a storm tide inundation model of Cyclone Yasi run over varying water levels to simulate sea level rise. TC Yasi was a very destructive and powerful tropical cyclone that made landfall with a category 5 intensity on the southern tropical coast near Mission Beach, Australia between midnight and 1am early on Thrusday 3rd February, 2011. ArcGIS is used to assess the impact of inundation across various indicators such as area of land, population impacted and lengths of roads inundated. By comparing the impact of the inundation for the model runs at various water depths the relationship between Storm Tide Impact and sea level rise is identified. Our study provides insight into the future behavior of Storm Surge events as sea levels rise that can inform climate change adaptation planning and vulnerability assessments. This comparison of the modelled storm surge inundation depth for Cyclone Yasi considers cyclone wind and pressure fields generated with parametric techniques such as Holland et al. (2010) wind field profile. The storm tide was simulated using Mike 21 hydrodynamic software with offshore bathymetry obtained from multiple local, state and federal agencies and adjusted to AHD and the land elevation was obtained from 1-m LiDAR data supplied by the Queensland State government.