tidel

Tidel is a provisional term used in coastal science to describe a dimensionless index that characterizes the effectiveness of tidal forcing at a given location. It summarizes how a site responds to the tidal cycle by combining information about tidal amplitude, timing, and waveform shape with local bathymetry and shoreline geometry.

Etymology and scope: The term blends tidal and level and was proposed in the early 2020s as a way to standardize comparisons of tidal potential across harbors, estuaries, and coastlines. As of now, tidel is not part of official hydrodynamic nomenclature, and several definitions have circulated.

Definition and components: A tidel consists of three components: amplitude ratio (R), phase lag (P), and waveform asymmetry (A). The index is typically computed from tide gauge records and hydrodynamic models using a reference tide at a benchmark location. Higher tidel values indicate stronger tidal influence relative to the reference.

Calculation and measurement: Data from long-term water level sensors, tidal constituents, and shoreline orientation are used. R = observed tidal range / reference range; P is the difference in timing of high tides; A captures asymmetry between flood and ebb. The exact formula varies by study.

Applications and limitations: Tidels have been used to compare tidal energy potential, inform flood risk assessments, and guide harbor design. Because definitions vary and reference conditions differ, tidel is not universally adopted, and results should be interpreted with attention to methodology.

See also: tidal range, tide gauge, coastal hydrodynamics.