Coastal Inundation Model

Overview

Flooding caused by sea water is referred to as coastal inundation. It can be caused by high tides, in combination with elevated sea level driven by wind and low air pressure, the size and frequency of waves and the dynamics at the sea-land interface. Coastal inundation events are exacerbated by rising sea levels. Sea levels rise for two reasons: the first is the added water from the melting of ice on land (floating ice does not add to sea level as it melts), the second is from thermal expansion of the oceans as the seas warm.

Local Context Data Use

The Climate Risk Engines also include an adjustment of the effects of land movement. This accounts for the fact that as well as general sea level rise, some continents are moving upward or downward. If the land is moving down because of tectonic actions, the height of mean sea level at that location is increasing above and beyond anthropogenic sea level rise.

Baseline Hazard Data

Coastal inundation data is based on national tidal gauges. These tide gauges provide a spectral probability distribution of tide levels, including extreme sea events.

Climate Change Projections

The average global sea level is rising by 3.2 mm per year (NASA 2020). The U.S. Government's National Oceanic and Atmospheric Administration (NOAA) report includes projections for what they refer to as 'high' and 'extreme' sea level rise scenarios, with increases of 2 m and 2.5 m of sea level rise by 2100, respectively. The 2021 IPCC report also allows for the possibility of 2 m sea level rise by the end of the century. Thus, the results for the ‘higher sea level rise range’ should be considered less likely, but possible. The Climate Risk Engines includes an intermediate projection from the suite of curves developed by Haigh et al (2014) using a default setting of 1.5m by 2100. The range of SLR projects in the Climate Risk Engines are listed and graphed below. • NOAA Low 0.3 m • Intermediate-Low 0.5 m • NOAA Intermediate 1.0 m • Intermediate-High 1.5 m • NOAA High 2.0 m Figure 7: Comparison of SLR projections