Mathematical Formulations for Three Components of Hydroperiod in Tidal Wetlands

摘要

Hydroperiod has numerous ecological function and effective methods for calculating hydroperiod would be valuable for different ecological or biological studies. However, accurate computation of hydroperiod remain challenging mainly due to absence of accurate mathematical formulation. Additionally, computing hydroperiod is complex due to the daily fluctuating water levels from tides, wind, river flows, and other meteorological events. This research presents quantitative formulations for three components of hydroperiod (flooding depth, frequency, and duration) directly from the physical dynamics of water surface movement in a tidal wetland. A set of National Oceanic and Atmospheric Administration (NOAA) tide gauges along the U.S. West, East, and Gulf coasts are selected to demonstrate the application of the new formulations. The computational results in terms of duration are compared with Morris non-dimensional depth (D) of hydroperiod. The comparison indicates that D is a linear-triangular approximation of sinusoid tide curve and it would generally be a good estimate of the duration component of hydroperiod within the tidal range and the accuracy of D depends on geographic location of the stations that determine the tidal regimes. Whereas the proposed formulation is not limited to variations in tide regimes and can be used as a powerful tool to determine hydroperiod.