A LIFE-CYCLE MODEL FOR WAVE-DOMINATED TIDAL INLETS ALONG THE NORTH AMERICAN, ATLANTIC COAST: PRIMARY FACTORS INFLUENCING INLET EVOLUTION

A regional overview of 104 wave-dominated tidal inlets along the U.S. Atlantic coast, U.S. Gulf coast, and Canadian Gulf of St. Lawrence coast yielded a generalized life-cycle model that recognized the rotational nature of wave-dominated tidal inlets while they were active. Rotational behaviors of tidal inlets were documented and analyzed from historical nautical charts, low-altitude aerial photography, and LiDAR surveys. Wave-dominated tidal inlets may form by landward- or seaward-directed island breaching and are classified into three categories based on inlet channel rotation behavior as referenced to net longshore sediment transport direction: downdrift direction, updrift direction, or little-to-no rotation. Channel rotation of wave-dominated tidal inlets appears to be primarily controlled by the lateral shifting of the flood-tidal delta depocenter in response to available estuarine accommodation space. Flood-tidal delta deposits will fill and thus exhaust accommodation space locally within the estuary (i.e., creating bathymetric highs), and over time, cause the tidal inlet to become less hydraulically efficient. External influences such as fluvial input, pre-existing backbarrier channels, and impeding salt marsh will also influence inlet channel rotation behavior. Storm events may rejuvenate the tidal inlet by entraining sediment within the flood-tidal delta, thus increasing the local accommodation space. The natural evolution of a wave-dominated tidal inlet typically is to rotate, wane, and close because of excess sediment deposition within the flood-tidal delta. The primary variables that are responsible for overall tidal inlet rotation are estuarine accommodation space, tidal prism, and sediment supply to the flood-tidal delta. Wave-dominated tidal inlets which rotate follow a six-stage evolutionary model; whereas, little-to-non rotating wave-dominated tidal inlets follow a five-stage evolutionary model.