A New Framework for Coastal Erosion Early Warning Systems
Abstract
Effective coastal erosion Early Warning Systems (EWSs) can provide critical lead time, prior to an advancing storm, for coastal communities to take action to mitigate or prevent threats caused by severe and rapid changes to beach morphology. One commonly-adopted conceptual framework which may be used by an EWS to describe coastal hazards is the Sallenger Storm Impact Scale (SSIS). This scale characterizes the severity of coastal storm impacts based on the vertical extent of the Total Water Level relative to the beach and dune profile. On wave-dominated coastlines however, where storm impacts are often caused by a horizontal recession of the coast, the usefulness of an EWS based on such a framework is unclear.
To assess the effectiveness of an EWS using the SSIS framework on wave-dominated coastlines, the impacts of a severe coastal erosion event spanning over 400km of coastline in SE Australia were hindcast. Wave and water level measurements were collected along with pre- and post-storm beach profiles at 100 m alongshore intervals over 177 km of sandy beaches within this region. The TWLs were hindcast using an empirical wave runup model and compared to dune elevations to hindcast one of four storm impact regimes described by the SSIS. By comparing the hindcast regimes to the observed regimes, it was found the EWS identified the correct regime at 65% of locations. Although the EWS achieved reasonable accuracy, a key finding of this study was that the usefulness of the SSIS for wave-dominated coastlines was found to be limited, considering that 98% of locations comprised either the swash or collision regimes only. In particular, the collision regime was inadequate in distinguishing between locations of significant dune erosion (causing residential property damage) and locations where dune erosion posed no immediate threat. To address this, a new conceptual framework suitable for wave-dominated coastlines is proposed whereby impacts are primarily due to erosion rather than the TWL. This new framework, based on shoreline response and dune volume change, is likely to significantly improve the effectiveness of EWSs by increasing the level of detail of forecast erosion hazards and allow authorities to better prioritize pre-storm preparations.- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFMEP13B..06L
- Keywords:
-
- 3020 Littoral processes;
- MARINE GEOLOGY AND GEOPHYSICS;
- 4315 Monitoring;
- forecasting;
- prediction;
- NATURAL HAZARDS;
- 4316 Physical modeling;
- NATURAL HAZARDS;
- 4217 Coastal processes;
- OCEANOGRAPHY: GENERAL