GEOMORPHIC CHANGE OF SALT-MARSH TIDAL CREEK NETWORKS IN THE DYFI ESTUARY, WALES

Planimetric changer; of saltmarsh tidal creek networks in the Dyfi Est uary, Wales, have been mapped from aerial photographs dating from 1966 to 1989. Rates of these changes have been evaluated with reference to creek length and creek density. Creek densities have been increasing during their development, ranging from 8 up to 11 km km(-2). These cha nges are mainly attributable to the instability of the main Dyfi tidal channel, flood and storm surges, saltmarsh vegetation development, el evational differences of the estuarine intertidal zone and sea level f luctuations. Dissipation of tide and wave energies associated with sto rm surges is chiefly responsible for the morphological development of the Dyfi tidal creeks. The discontinuous stage-prism asymmetry hydrody namic model is applicable to explaining the Dyfi estuarine tidal creek development. A form-process feedback between the vertical growth of t he Dyfi saltmarsh surface and the hydrodynamics of its network is also important in governing the Dyfi tidal creek network development. The rapid development of the Dyfi tidal creek networks could result in the loss of the Dyfi estuarine wetland.