Erosion of Coastal Systems
Authors: Esteves, L.
Editors: Finkl, C.W. and Mokowski, C.
Coastal erosion is both a natural process important for the maintenance of dynamic equilibrium of coastal systems and a major hazard to human occupation along dynamic shorelines. Most often, it results from a combination of natural and human-induced factors acting at a range of scales. The importance of each specific factor will vary geographically and will depend on the temporal scale in which the system is being analysed. Considering natural processes, erosion is often a temporary state associated with phases of natural cycles that can vary from short (e.g. seasonal increase in wave energy) to very long durations (e.g. sea-level rise during interglacial periods). Poor understanding about the duration of these cycles or about the spatial scale of associated coastal changes have led to human interferences that often result in enhanced erosion. Human-induced erosion is becoming pervasive worldwide both due to in situ direct impacts (e.g. due to coastal engineering works) and indirect impacts of inland activities (e.g. retention of sediment by dams). In many locations, climate change may result in increasing storminess and sea-level rise, which are likely to enhance existing coastal erosion or trigger a shift towards erosion. This is a particular concern where urban areas or coastal infrastructure are occupying dynamic spaces (areas where natural coastal change is expected) in low-lying coasts. There is a growing trend towards renaturalisation of coastal areas (e.g. managed realignment) as a more sustainable approach to manage flooding and erosion risks with added environmental benefits. However, a key challenge to coastal management remains, the urgent need to ensure that existing issues are not made worse by ill-informed policies or management decisions driven by short-term gains (e.g. allowing occupation in erosion-prone areas or persisting with hardening of shorelines where other options, including retreat, are more sustainable albeit more complex).