SUSPENDED SEDIMENT IN THE LITTORAL ZONE AT 

 VENTNOR, NEW JERSEY, AND NAGS HEAD, NORTH CAROLINA 



hy 

 John C. Fairoh-ild 



I. INTRODUCTION 



Much o£ the sand transport along beaches occurs in suspensions. These 

 suspensions are entrained by wave-induced water velocity near the bottom, 

 particularly in the zone extending from seaward of the breaker line to the 

 runup limit. Such suspensions are important to coastal engineering because, 

 once suspended, the sand can be moved by currents with mean velocities too 

 small to initiate sediment transport. For example, weak longshore currents 

 may be very effective in transporting sand in the longshore direction, once 

 that sand has been stirred up by the onshore-offshore motion of waves cross- 

 ing the surf zone. 



The relative importance of transport in such suspensions, measured as 

 a fraction of total littoral transport, is presently unknown, but there is 

 evidence that sand transport in suspension may be the significant fraction 

 of longshore transport (Calvin, 1973) . This study examines two extensive 

 collections of data on sediment suspensions in the surf zone to determine 

 the characteristics of such suspensions and to judge the relative impor- 

 tance of sediment suspensions to the total littoral transport. 



The principal variables considered in this study are listed in Symbols 

 and Definitions. The concentration of the suspension, C, is considered 

 to be a dependent variable determined by an unknown function of sediment 

 size (d™) , distance from breaker line (S) , water depth (d) , elevation above 

 bottom (E) , wave height (R) , wave period (T) , and breaker type: 



C = f (d„, S, d, E, H, T, Breaker Type) . (1) 



Most of this report attempts to isolate the effect of the independent var- 

 iables, grouped as sediment size (d^) , position (S,d,E), and wave conditions 

 (H, T, Breaker Type), on suspended-sediment concentration, C, for data 

 collected from City Pier, at Ventnor, New Jersey, in 1965 and Jennette's 

 Pier at Nags Head, North Carolina, in 1964. 



II. FIELD DATA COLLECTION PROCEDURES 



1. Piers and Profiles . 



Suspended- sediment data were collected at several locations along the 

 fishing pier at each of the study sites. Figure 1 is an aerial photo of 

 Jennette's Pier. The length of the pier deck is about 780 feet (238 meters) 

 and the deck elevation is about 18 feet (5.5 meters) above mean water level 

 (MWL) . Figure 2 is an aerial photo of City Pier. The length of the pier 

 deck measured from the concrete wall on the landward side of the boardwalk 



