ABSTRACT OF THE THESIS 
spatial and Temporal Variations in 
Barred and Non-Barred Topographies, 
Sandy Hook, New Jersey 
by Lindsay D. Nakashima, Ph.D. 
~hesis Director: Professor Norbert P. Psuty 


Results are presented from an examination of adjoining 
barred and non-barred nearshore topographies for a portion 
of the oceanside barrier spit shoreline at Sandy Hook, New 
Jersey. An examination was made of the hypothesis that 
differences or longshore variability in the sediment budget 
would exist in each topography, and that the controls on 
equilibrium would be linked to differences in hydrodynamic 
conditions as well as the modes, rates and pathways of 
sediment transfers. 


Results show that gross shoreline changes during a 146 year interval describe wide variability. Net retreat typifies the shoreline but the most conspicuous variation occurs in the longshore direction at the break in shoreline orientation which has migrated 1 kilometer northward during the last 50 years. The entire shoreline exhibits a negative sediment balance that varies by a factor of 2 between the non-barred and barred systems. 

Sediment flux computations reveal several trends that 
point to a longshore variation in sediment budget: i) 
non-barred sediment transport exceeds the barred system by a 


factor of at least 3; ii) crest and trough subenvironments 
exhibit the greatest transport in the barred system; iii) 
bed load dominates over suspended load within an order of 
magnitude quantity per breaker; iv) quantity of sediment 
entrained decreases within an order of magnitude from 
plunging, spilling to surging breaker types; and v) 
variability with the CERC total transport equation exists as 
an overestimate within an order of magnitude difference for 
the barred system, and as an underestimate for the 
non-barred system. 


Analysis of wave process and sand transport data 
reveals breaker height is the major driving force that 
describes the variability in the sediment budgets. The 
longshore current speed, breaker angle, and nearshore slope 
are also important variables that describe the variability 
in sand transport and demonstrate the effect of shoreline 
orientation in the barred system. 


Barred development and equilibrium are affiliated with 


1 

plunging breaker vortices under storm conditions and inshore 
circulation associated with instability mechanisms that are 
driven by normal swell waves. In comparison instability 
theory is inapplicable to the non-barred system, since 
higher energy wave conditions and a considerably shorter 
mixing length generate a non-cellular flow field. 


iii