Aeolian processes and dune fields in estuaries

Dunes occur in numerous locations in estuaries despite constraints to active aeolian transport caused by the paucity and small size of sand beaches. Examination of dune characteristics in two large estuaries in the northeastern United States (Raritan Bay and Delaware Bay) reveals that active foredunes formed by natural processes are small (usually <1.5 m high) owing to low wave energies and small beach dimensions. Many of the largest dunes (=5.0 m high) did not form solely by modern bayside processes, indicating that factors other than waves and winds generated within the estuary play a major role in creating dune topography. Accordingly, a genetic classification is suggested for analysis and interpretation of these landforms. Categories include: (1) ocean-dominated dunes that occur near estuarine openings; (2) inherited dunes that were once ocean-dominated forms that are reworked by estuarine processes; (3) foredunes; (4) foreland dunes; (5) human-created dunes, including bulldozed dunes, dunes created using sand fencing or vegetation plantings, dikes and second-generation forms; and (6) relict dunes created by processes operative within estuaries but under conditions that differed from present.