Dynamics of Coastal Fluid Muds in Low-, Moderate-, and High-Tide-Range Environments

Abstract

Field studies of intertidal and subtidal fluid muds in low-, moderate-, and high-tide-range environments have revealed several similarities in process-response behavior despite the wide range in tidal energy. Using data from Louisiana (tide range 0.5 m), Surinam (tide range 2.0 m), and South Korea (tide range 5–9 m), examples are given for the unifying characteristics of (1) extreme wave attenuation, (2) high suspended-sediment concentration, and (3) rapid migration and "shifting" of soft muds. The loss of incoming wave energy results in natural protection to shorelines that are fronted by fluid muds. The opportunity thus exists to predict areas of future progradation and erosion from knowledge of fluid mud behavior. Fluid muds can be easily resuspended by small waves, and the high concentrations of suspended sediments in regions of mudshoals suggest that net transport rates can be enormous even under relatively weak currents. In addition to serving as temporary and transitory storehouses for littoral sediments, intertidal mudflats and subtidal mudshoals can become "welded" to the shoreline and colonized by vegetation in a single season.Key words: fluid mud, fine-grained sediments, wave attenuation