DOMINANT 

 TRANSPORT 

 DIRECTION 



EBB-TIDAL DIITA 



(after Hayes, 1975) 



Figure 4-61. Typical ebb-tidal delta morphology. (The ebb jet maintains a 

 deep central trough, the main ebb channel, flanked by channel margin 

 linear bars and wide arcuate swash platforms. Wave action on the 

 swash platforms generates landward-migrating swash bars. Marginal 

 flood channels separate the channel margin linear bars from the 

 adjacent beaches. Different patterns indicate which areas are 

 dominated by ebb currents, flood currents, or waves.) 



(c) A lunate, subaqueous terminal lobe deposited seaward of the main 

 channel by ebb currents, which normally has a large ebb-oriented slip face 

 around its seaward margin. 



The topography of the ebb-tidal delta of the lyferrimack River Inlet, 

 Massachusetts, is illustrated in Figure 4-62. This inlet shows the typical 

 downdvift offset on the south side of the inlet (i.e., the side downdrift of 

 predominant wave action and littoral transport). This offset is a feature 

 caused by a vave sheltering of the downdrift side of the inlet by the ebb- 

 tidal delta. As noted in Section IX, 2, this downdrift side of the inlet also 

 experiences a littoral current reversal under waves from the dominant wave 

 direction because of refraction around the ebb-tidal delta complex. 



Although many inlets have a downdrift offset, there are also inlets which 

 are offset in the updrift direction, so ebb-tidal delta geomorphology alone is 

 not sufficient to provide the information necessary to determine the dominant 

 sand transport direction. 



4-150 



