36 
5 Beach-Fill Planform 
Adjustment 
The prefill shoreline at the northernmost portion of the hot-spot region 
protrudes significantly seaward of the adjacent shoreline because of the presence 
of infrastructure and the subsequent protection of this infrastructure with a 
seaward-protruding seawall and a curved groin (Groin 44). The planform design 
of the beach fill adds a 100-ft design berm to the existing shoreline, which 
results in the beach-fill planform protruding seaward similar to the structure- 
protected prefill shoreline. It is hypothesized that the severe loss of beach-fill 
material at the hot spot is related to this seaward protrusion of the beach-fill 
planform and that the beach fill will tend to adjust towards a shape and 
orientation similar to the offshore bathymetric contours. 
As part of this analysis, three-dimensional bathymetric models were 
developed from beach profile surveys to evaluate the planform evolution of the 
shorelines and bathymetric contours. In addition, bathymetric change between 
sequential beach profile surveys was computed to give locations of eroded and 
accreted material. This analysis identifies trends in beach-fill evolution and 
relates these evolutionary trends to the development of the hot spot. 
Data Source and Bathymetry Models 
Data used in the analysis of beach planform evolution were those collected 
for the purpose of computing beach-fill pay quantities. These beach profile 
surveys were measured at various stages of completion of the beach-fill project 
at approximately 100-ft intervals along the beach-fill reference line over the 
particular reach of the project being surveyed. The beach profile surveys 
typically extend from the beach-fill reference line (which generally follows the 
seawall or revetment) to approximately 1,000 ft seaward, with maximum depths 
ranging from 20-25 ft. In addition to the beach profile data, a set of aerial 
photographs taken in April 1996 were used to digitize the mean high water 
(mhw) shoreline for that time and landmarks (streets, coastal structures, etc.) 
useful in relating the bathymetric models to the physical domain. 
Chapter 5 Beach-Fill Planform Adjustment 
