Coastal dunes: sensitive or not

This paper introduces a classification of coastal dune systems into two main morphodynamic classes, namely retentive and transgressive dune systems. Retentive systems include coastal dune types where sand accumulation within vegetation is dominant over other processes. In this category we include such morphological types as hummock dunes, foredunes, and retention ridges, including sub-environments such as precipitation ridges that form the landward boundary of transgressive dunefields. Transgressive systems include those coastal dune types where sand transport is dominant over other processes, and the dunes are unvegetated and mobile. In this category we include such morphological types as parabolic dunes, reversing transverse dunes, barchans, seif dunes, transgressive sheet dunefields and headland-bypass dunefields. Components of the two main morphodynamic types of coastal dune systems range in sensitivity from sensitive to robust. Retentive dune systems, being vegetated, are sensitive and fragile. Mobile dunes that form the major component of transgressive dune systems are robust and resilient. This morphodynamic classification is particularly useful because the two types of dune systems have diametrically opposed sensitivities and hence different management requirements.