To determine the equilibrium cross-sectional areas and their stability for a single inlet system, Escoffier's stability concept is used. Based on a balance between wave-driven import and tide-driven export, he reasoned that the inlet is in equilibrium when the inlet velocity amplitude equals the equilibrium velocity. The velocity amplitude is calculated from u = πP/AT with P is tidal prism, A is cross-sectional area and T is tidal period. The equilibrium velocity is calculated by eliminating the tidal prism in this equation using one of the cross-sectional area -tidal prism relationships. For a velocity amplitude larger than the equilibrium velocity, the inlet scours, when smaller than the equilibrium velocity the inlet shoals. This can be visualized with the so-called Escoffier Diagram, which consists of a closure curve and an equilibrium velocity curve. The closure curve shows the amplitude of the inlet velocity as a function of cross-sectional area. Using the Escoffier Diagram, it is shown that generally two equilibrium cross-sectional areas exist; the larger of the two is stable while the smaller one is unstable. The same conclusion is arrived at using a linear stability analysis. As an example, the Escoffier method is applied to Pass Cavallo (TX).