1.3. Study Hypotheses and Main Conclusions 



This section summarizes the main study conclusions. The material is intended to serve as a 

 guide through the substantial detailed discussion that follows. Two hypotheses underlie this 

 study and assessment of coastal change. First, it is assumed that longshore sediment transport 

 predominantly controls change in the beach that is inundated under normal (day-to-day, and non- 

 storm) tide. Longshore transport can produce either accretion or erosion, depending on the local 

 balance of sand entering and leaving an area of the beach. The Harbor entrance is a complete 

 littoral barrier and alters longshore sediment transport in its vicinity. Second, erosion of the 

 upper beach (above the elevation reached by normal tide) and dune is caused primarily by storms 

 in a cross-shore sediment transport process unrelated to the Harbor. These two processes, 

 longshore transport and cross-shore transport, are depicted in Figure 1-4. 



Changes in shoreline position and beach volume through time at the properties of the two test 

 plaintiffs were calculated from beach-profile survey measurements. Additionally, storm impacts 

 were estimated with a numerical model to substantiate and interpret conclusions drawn from the 

 measurements. Main conclusions are as follows: 



1.3.1. Applegate Property 



From August 12, 1981 (time of purchase), to December 8, 1997 (representing the present), 

 the beach eroded and the shoreline receded at the Applegate property. The sand eroded from the 

 beach fronting the Applegate property was removed from material placed during the 1974/75 

 U.S. Army Corps of Engineers (USACE) beach fill. The natural beach north and adjacent to the 

 property prior to fill placement just recently began to erode (as shown on the December 8, 1997, 

 beach profile at R-7). From August 12, 1981, to December 8, 1997, the MHW shoreline receded 



Analysis in this report makes a distinction between the morphological features of the beach and the dune . For most 

 discussion, unless otherwise qualified, the word beach refers to the region of dynamic boundaries extending landward from 

 the edge of the water to the approximate 8-ft elevation NGVD. Qualitatively, the beach is where one can walk or place a 

 blanket to sunbathe. The dune extends upward from the back beach with a near-vertical face to an elevation of 

 approximately 10-15 ft NGVD. Daily, sediment is transported along and across the beach by water and wind, according to 

 the level of the ordinary tide, wave conditions, and wind velocity. In contrast, the strong sediment-transporting forces of 

 waves and currents only reach the dune when the water level is elevated during a storm or, depending on width of the 

 beach, during a very high tide. Sediment is removed from a dune if waves and currents act upon it. As sand is removed 

 from the dune and enters the water, it can move both alongshore and across shore. 



Longshore sand transport refers to the movement of sand along the coast, parallel to the shoreline. On the Brevard 

 County coast, daily longshore sand movement is either to the north or to the south. Erosion and accretion by longshore 

 sand transport is a continual process associated with currents produced by incident breaking waves. Changes in beach 

 shape and shoreline position associated with longshore sand transport tend to be gradual in the sense that the change 

 typically cannot be observed in a day. Change in beach shape is a long-term, gradual process. 



Cross-shore sand transport refers to the movement of sand perpendicular to the coast as either onshore or offshore. 

 Under the milder waves of summer and the normal or small storms of winter, the beach accretes and erodes with a 

 seasonal pattern. For strong storms, those with high water levels (storm surge) and higher waves of longer wave period, 

 erosion by cross-shore transport is a short-term or event-driven process occurring over a matter of hours or days. 

 Significant erosion can occur on a wave by wave basis during extreme events with high water levels that allow waves to 

 attack directly against the dune. Under such storms, the dune face recedes as the dune erodes. 



Chapter! Introduction "]-5 



