Characterization of time and spatial scales of a migrating rivermouth
Dane K. Behrens, Fabián A. Bombardelli, John L. Largier, and Elinor Twohy
Coastal inlets regulate tidal conveyance in a variety of systems ranging from small tidal lagoons with no freshwater inflow to estuaries at the terminus of significant rivers [Shuttleworth et al., 2005; Kraus et al., 2008]. The importance of these systems stems from their association with unique ecological environments [Gladstone et al., 2006] and harbors of economic relevance [Escoffier and Walton, 1979]. While many coastal inlet systems maintain a state of morphologic equilibrium and vary little in position and geometry with time, inlets which migrate or experience seasonal or sporadic closure occur in virtually every arid and semiarid region of the world [Ranasinghe and Pattiaratchi, 2003]. Inlet migration [Galvin, 1971; Aubrey and Speer, 1984] and closure [Bruun and Gerritsen, 1960; Escoffier and Walton, 1979; Ranasinghe and Pattiaratchi, 2003] have received much attention in the last half-century. However, both the short- and long-term dynamics of coastal inlets still remain poorly understood [Goodwin, 1996]. Attempting to understand how these systems react to climate change will be difficult without a strong understanding of the mechanisms involved, and the level of inlet variability ascribed to climate change versus alternate sources of variability.
The scientific goal of this study is to identify consistent behavioral patterns of coastal inlets with significant seasonal river influence at various time and length scales; in particular, inlet migration, shape, width, length and closure frequency. We aim to connect short- and long-term mani festations of these behaviors to climate patterns ranging from short-term changes in wave, tide, and river conditions to large-scale changes associated with El Nin˜o-Southern Oscillation (ENSO) events. Knowledge of these connections will allow further research into the effects of sea level rise and changing wave and precipitation conditions on behavioral patterns of this and other river mouth systems around the world.
