Sea-Level Rise Driving Increasingly Predictable Coastal Inundation in
Sydney, Australia
Abstract
As global mean sea level (GMSL) continues to rise, thresholds
corresponding to coastal inundation impacts are exceeded more
frequently. This paper aims to relate sea-level rise (SLR) observations
and projections to their physical on-the-ground impacts. Using a large
coastal city as an example, we show that in Sydney, Australia,
frequencies of minor coastal inundation have increased from 1.6 to 7.8
days per year between 1914 and present day. We attribute over 80% of
the observed coastal inundation events between 1970 and 2015 to the
predominantly anthropogenic increases in GMSL. Further, we find that
impact-producing coastal inundation will occur weekly by 2050 under
high- and medium- emission/sea-level rise scenarios, and daily by 2100
under high emissions. The proportion of tide-only coastal inundation
events (i.e. where no storm surge is required to exceed flood
thresholds) will increase with SLR, such that most coastal inundation
events, including those considered historically severe, will become a
predictable consequence of SLR and astronomical tides. These findings
are important for coastal managers as frequency, severity and
predictability of inundation impacts can all now be related to the
amount of SLR (e.g. a planning allowance or SLR projection). By
incorporating known historical inundation events, this allows
contextualization, visualization and localization of global SLR and the
changing nature of future coastal inundation risk.