ANNUAL DATUM BASED SHORELINE CHANGE ENVELOPE ON A BARRIER/CUSPATE FORELAND COAST CAPE CANAVERAL, FLORIDA

Estimating the shoreline response to rising sea level is often accomplished by extrapolating long-term retreat trends into the future. However, event-scale changes to the shoreline may place it in a state that is more sensitive to future sea-level rise. Consequently, establishing annual shoreline change envelopes (SCE) and comparing it with long-term data sets is important in establishing the current state of the shoreline. To examine the annual SCE at Cape Canaveral, FL, a campaign of 13 monthly surveys began in May 2009 on the full moon-Spring Tide cycle and continued on the lunar month through May 2010. This study documents monthly changes in the datum-based mean-high-water (MHW) shoreline position and is being conducted in conjunction with the examination of shoreline position proxies derived from 51 aerial and satellite images collected from 1943 through 2010.

Cape Canaveral is a large barrier island and cuspate foreland along the east coast of FL. Beach morphology at the cape is affected by both tropical and extra-tropical cyclones, each with a unique wave pattern distribution. Surveys were conducted using a kinematic GPS system mounted on a trailer towed by an all-terrain vehicle. Data was collected at 0.5-meter horizontal intervals along multiple (8-12) along-shore transects following slope breaks.

Dean et al. (1998) examined shoreline change along the cape from 1875 to 2007, and noted a sinusoidal pattern of erosion and accretion intensifying southward along the cape. On the northern border of Kennedy Space Center in an area where previous observations indicated <0.1 m/yr decadal change of the shoreline, the annual SCE was between 10 and 15 m with a net annual retreat of 1 to 5m. Areas of historically higher retreat rates (~0.5 m/yr) in the central portion of the study area experienced a wide variation in the annual SCE with shoreline position changes ranging from 10 m to 25 m, and net change of 5 m retreat to 11 m of advance. In an area of historical accretion at False Cape (>1 m/yr advance), the annual SCE demonstrated the greatest change, ranging from 10 m to 29 m, with a net change from 5 m of retreat to 5 m of advance. This pattern, very different from the long-term change of Dean et al. (1998), demonstrates that short term monthly change does not necessarily reflect the long term decadal pattern of change found along a coastline.