VII. INLETS 



by 

 Richard A. Sager and Lyndetl Z. Rales 



1. Introduction . 



The coastal inlet is a complex part of the coastal environment. 

 The three primary forces of importance to the coastal inlet are lunar- 

 dominated ocean tides, winds, and freshwater inflow. These forces inter- 

 act in the ocean, bay, and inlet proper to produce many phenomena that 

 affect the inlet. Among these phenomena are: (a) tidal currents, (b) 

 littoral currents, (c) wind waves, (d) density currents, (e) changes in 

 water levels due to lunar tides, (f) wind wave runup, (g) currents gen- 

 erated by wind-water surface interaction, (h) littoral transport of ma- 

 terial to the inlet, (i) wind transport of material to the inlet, and 

 (j) freshwater transport of material to the inlet. A true physical model 

 requires the accurate simulation of all of these phenomena active at a 

 particular inlet. This simulation is not only beyond the capability of 

 present physical modeling, but beyond the capabilities of any known sim- 

 ulation technique. The physical model does, however, provide a means of 

 investigating the effects of a significant number of these phenomena. 

 For many cases, this will allow an effective understanding of what does 

 or could occur at a tidal inlet. 



Although any one of these phenomena could be particularly important 

 for understanding conditions at an inlet, this section discusses only the 

 more critical phenomena affecting an inlet; i.e., physical modeling of 

 tidal oscillations, tidal currents, tidal current -wind wave interaction, 

 and the movement and deposition of material within the inlet complex by 

 hydraulic forces. The physical modeling of wind-transported material and 

 the effects of density currents (sometimes vital to the understanding of 

 coastal inlets where large freshwater sources can act on an inlet) are 

 not discussed in this section. Physical modeling of density current phe- 

 nomena is discussed in Section III; modeling of the littoral transport of 

 material approaching the inlet is discussed both in this section and in 

 Section V. Many aspects of wind wave modeling particularly important to 

 physical modeling of tidal inlets are briefly covered in this section; 

 details of physical modeling of wind waves are discussed in Sections II, 

 IV, and VI. 



Studies in tidal inlet models are generally directed to development 

 of methods for maintaining an effective navigation channel through the 

 inlet, but often other aspects must also be investigated. Problems that 

 can be investigated by physical inlet models are: 



(a) Stabilization of navigation channel dimensions and 

 location. 



(b) Structural dimensions of jetties, etc., and location 

 and configuration. 



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