COASTAL DUNES - SENSITIVE OR NOT

This paper introduces a classification of coastal dune systems into tw o main morphodynamic classes, namely retentive and transgressive dune systems. Retentive systems include coastal dune types where sand accum ulation within vegetation is dominant over other processes. In this ca tegory we include such morphological types as hummock dunes, foredunes , and retention ridges, including sub-environments such as precipitati on ridges that form the landward boundary of transgressive dunefields. Transgressive systems include those coastal dune types where sand tra nsport is dominant over other processes, and the dunes are unvegetated and mobile. In this category we include such morphological types as p arabolic dunes, reversing transverse dunes, barchans, self dunes, tran sgressive sheet dunefields and headland-bypass dunefields. Components of the two main morphodynamic types of coastal dune systems range in s ensitivity from sensitive to robust. Retentive dune systems, being veg etated, are sensitive and fragile. Mobile dunes that form, the major c omponent of transgressive dune systems are robust and resilient. This morphodynamic classification is particularly useful because the two ty pes of dune systems have diametrically opposed sensitivities and hence different management requirements.