Exposure and inundation statistics from published tide tables

An algorithm to extract exposure and inundation data from up to 1 year of published tide table data has been developed and implemented on a microcomputer. The timing of individual exposure-inundation events is calculated, along with the duration of each episode for a range of levels above tidal datum. This provides a forecast of beach accessibility. Subsidiary programs derive exposure-inundation statistics such as the total, mean, and maximum duration of each episode. These factors influence the vertical zonation of beach environments. The vertical velocity of the tide also is estimated for each level on the beach. This can be converted to over-beach velocity providing beach gradient is known. Another program calculates the duration of “still-water level” within selected vertical ranges, providing an index of waveenergy distribution, ice grounding phenomena, and probability of oil pollution. The approach has been tested at Frobisher Bay, Northwest Territories, Canada where maximum tides of as much as 10 m range cover extensive tidal flats. Maximum exposure and inundation times increase steadily up to minimum high and low tide respectively, beyond which they increase rapidly, but irregularly. Tide velocities exceed sediment transportation thresholds, especially in the mid-tidal range. Still-water duration peaks at both the mid-high and low-tide levels for simple semidiurnal tides. The programs provide an inexpensive way of categorizing tidal effects on the beach environment.