In the original morphologic model (Kraus 2003), the transport rates were

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^

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parameterized as *Q*S = *Q*S (1 - *x */ *x*e ) and *Q*B = *Q*B (1 - *z */ *z*e ) , in which *Q*S and

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breach-forcing conditions. Closed-form solution of the two equations was

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found possible if *Q*B and *Q*S equaled a constant rate Q , leading to solutions of

the form x = *x*e [1 - *f *( *x*) exp(-*t */ τ)] and z = *z*e [1 - *g *( *z*) exp(-*t */ τ)] . These

solutions describe an exponential growth toward equilibrium at a rate governed

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by the morphologic time scale τ = *x*e ze L / *Q *. Eqs. (1) and (2) possess

characteristics encountered in chaos theory. Therefore, the solution at early

stages strongly depends on the initial condition, contained in the functions *f *and

The original morphologic model represents the macro-scale process of

breach growth. The solution indicates time-dependent breach dimensions are

controlled by seven variables: initial width and depth of the breach, equilibrium

width and depth of the breach, width of the barrier island, and maximum or

initial net sediment transport rates at the bottom and sides of the breach.

The original model was limited in not accounting for the current that

transports sediment through the breach. The breaching model is extended here

by incorporating a 1-D inlet hydrodynamic model to calculate sediment

transport, as well as including longshore sediment transport and wave set up.

∆*x*

∆*x*

∆*z*

Figure 1. Definition sketch for rectangular barrier island.

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