Salt pans are commonly found in coastal marshes and play a vital role in
the marsh plants zonation. However, the correlation between these
hypersaline zones and the marsh hydrological conditions have barely been
characterized. This study numerically investigates the effects of
evaporation rate, tidal amplitude, and marsh platform slope on salt pan
formation, and found that salt pans can hardly grow in the intertidal
zone due to regular tidal flushing, while tend to form in the lower
supratidal zone, where evaporation is sustained. The accumulated salts
create an upward salinity gradient that trigger downward unstable flow.
The decreases of potential evaporation rate, tidal amplitude and/or
marsh platform slope strengthen the hydraulic connection between the
marsh surface and the underlying watertable, the key to sustaining
evaporation, and therefore result in thickener and wider salt pans.
These findings offer a deeper insight into the marsh ecohydrology and
guidance for their degradation prevention.