Figure 1. Inlet entrance morphology, East Pass, FL, 1990

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ERDC/CHL CHETN-IV-33

June 2001

to wave action and wave-induced currents. The attachment bar develops from material bypassed

around the ebb shoal complex, either arriving to or leaving from the shore. The attachment bar is

sometimes called the "tie-in" or "weldment" area. In the following, the terminology "ebb shoal"

refers to that portion of the ebb shoal complex located within the ebb jet. (Kraus 2000) The

combination of the ebb shoal, bypassing bars, and attachment bars is termed the "ebb shoal

complex." For the following discussion, it is convenient to define "inlet edge," labeled by red

dots in Figure 1, denoting the location where land and water join at the point of land

encroachment into the inlet. Two inlet edges exist, one on either side of the inlet. If an inlet is

stabilized with jetties, the inlet edges are located at the intersection of the shoreline and jetty.

Inlet Edge

Updrift

Attachment Bar

Updrift

Bypassing Bar

Ebb Channel Centerline

Inlet Centerline

Ebb Shoal

Proper

Inlet Edge

Downdrift

Bypassing Bar

Downdrift

Attachment Bar

Figure 1. Inlet entrance morphology, East Pass, FL, 1990

An idealized ebb shoal complex has an arcuate form, exhibiting symmetry with respect to the

entrance channel, a phenomenon consistent with turbulent jet theory. Figure 2 is a definition

sketch of the measurements discussed in this Technical Note that were made from interpretation

of aerial photographs. A more symmetrically shaped ebb shoal would tend to form if the left-

and right-directed longshore sediment transport rates were equal, the navigational channel

dredged straight out, and the main static factors of back-bay configuration, jetties, shelf

bathymetry, and geologic structure symmetric across the center line of the inlet. Morphologic

features and an inlet channel center line that deviate from the ideal situation are categorized as

asymmetrical.

In Figure 2, the variable L represents the distance from the shoreline (which was identified as the

water-beach interface for each individual measurement) to the seaward-most point of the ebb

shoal. The quantity Wc is the channel critical width, defined as the narrowest point between the