A LIFE-CYCLE MODEL OF WAVE-DOMINATED TIDAL INLETS ALONG THE CANADIAN AND UNITED STATES ATLANTIC COAST

A regional overview of wave-dominated tidal inlets along the Canadian and United States Atlantic coast yielded a generalized life-cycle model based on their breaching direction and rotational nature. Historical aerial photography from nine wave-dominated tidal inlets was analyzed for geomorphic features relating to inlet rotation. Three factors are critically important in the life-cycle of a wave-dominated tidal inlet: tidal prism, sediment supply, and estuarine accommodation space. Wave-dominated tidal inlets are formed by landward or seaward directed breaching and are classified into three categories based on inlet channel rotation direction: clockwise rotation, counterclockwise rotation, or non-rotation. Rotation of wave-dominated tidal inlets appears to be primarily controlled by the lateral shifting of the flood-tidal delta (FTD) depocenter in response to available accommodation space in the estuary. FTD deposits will fill local estuarine accommodation space, causing the tidal inlet to become less hydraulically efficient. In order for a wave-dominated tidal inlet to remain open, one of two scenarios must occur: lateral inlet migration or a rejuvenation event. A laterally migrating inlet will gain access to new accommodation space in the estuary. Tidal inlets that rotated counterclockwise in this study had FTD channels migrate downdrift and the inlet throat migrate updrift. Inlets that migrated in a clockwise fashion tended to have done so because of external influences on estuarine accommodation space or inlet hydrodynamics (i.e. rotation into a pre-existing backbarrier channel, impeding marsh platform or recurved spit). Intense storm events may increase the accommodation space for the FTD by breaching a more hydraulically efficient path or entraining and reworking FTD deposits. The wave-dominated tidal inlet life-cycle model shows rotating tidal inlets follow a six-stage evolutionary model, whereas non-rotating tidal inlets follow five-stages.