Quantified rates of geomorphic change on a modern carbonate tidal flat, Bahamas

Comparison of aerial photographs and ultrahigh-resolution remote sensing data reveals changes in the geomorphology of a modern carbonate tidal flat. In the 58 yr between acquisition of the two data sets, several tidal channels have extended headward more than 100 m, channel bars have stabilized, the shoreline has eroded as much as 50 m, the inland algal marsh locally has prograded as much as 90 m, and many mangrove ponds have increased in size. These changes over the known time interval allow quantification of the rates of these geomorphic processes and suggest rates of migration of landforms to several meters per year. Some observed rates appear to be different than rates averaged over the past several thousand years, however, possibly because of changes in storm activity or circulation patterns. These data illustrate the dynamic nature of the entire coastal tidal-flat system, not just the shoreline, and reflect the system's response to factors including relative rises in sea level. Keywords: Andros Island, remote sensing, sea level, sediments, carbonate, tidal flat, coastal.