Intracoastal tides of upper Laguna Madre, Texas

A l-yr record of hourly water level measurements from Upper Laguna Madre, Texas,indicates water level variations occur primarily in response to estuarine-shelf exchanges in 3forms. A dominant, semi-annual rise and fall of sea level is driven externally by thermohalineand dynamic processes in the Gulf of Mexico. Meteorologically forced variations in coastalsea level produce exchanges and thus intracoastal water level variations over time scales onthe order of 1 to 2 weeks. Astronomical tides are relatively small perturbations superimposedonto the longer-period processes.Water level data from Port Aransas, Texas, and Upper Laguna Madre are used to tracethe movement and damping of tidal motions from the coast, through Corpus Christi Bay tothe study site. Tidal crests move at approximately 4-5 km/hr, and the constituents are decreasedto less than 25% of their amplitudes at the coast. Tidal motions in Upper LagunaMadre are primarily at diurnal periods, and K₁ and O₁ constituent amplitudes are both onthe order of 2-3 cm. Comparison of tidal and non-tidal period water level variations indicatesthat tidal motions account for approximately 5% of the total observed variation in water level at this location.