Changing Coastlines at Cape Canaveral by Kara
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Changing Coastlines at Cape Canaveral By Kara Doran and Hilary Stockdon The USGS National Assessment of Coastal Change Hazards (NACCH) project works to quantify coastal change hazards including extreme storm impacts, long-term erosion, and sea-level rise along our Nation’s open-ocean coasts. Through extensive observation, modeling and prediction of these processes, scientists aim to gauge how U.S. shores have historically shifted, how past changes will affect their vulnerability to future hazards, and how coastal processes are shaping the coastline . Since 2008, scientists in the St. Petersburg Coastal and Marine Science Center have been working with NASA and the U.S. Air Force to understand coastal processes at Kennedy Space Center (KSC) and Cape Canaveral Air Force Station (CCAFS), and to provide scientific tools for decision-making. Figure 1. Low dunes near launch pads 39 A and B often overwash during storm events, transporting sand landward. Critical infrastructure may be buried or flooded. Additionally, significant landward transport of sand may lead to extensive shoreline erosion. Photo Credit: USGS. NACCH forecasts of coastal vulnerability combine dune heights and storm-induced water levels to estimate the likelihood of coastal change response (i.e., dune erosion, overwash, or inundation). Dune heights at KSC and CCAFB range from 2 to 8 meters (m) with the lowest elevations near launch pads 39A and B and along the Cape. In these areas, overwash is likely during winter or tropical storm events with offshore wave heights of 3 to 5 m and a 0.5 m storm surge. As the coastline has been subject to repeated hurricane, tropical storm, and winter storm impacts, the vulnerability of the KSC and CCAFS coasts has increased. In 1999, 20 percent of the coast was likely to overwash during a winter storm event compared to 30 percent in 2009, due to lower dune crest elevations in some areas (fig. 2). Figure 2. The overall vulnerability of KSC and CCAFS to overwash has increased with time, especially in areas with low dunes near the KSC launch pads and around the Cape. Basemap: ESRI, Digital Globe. NACCH also provides estimates of long-term coastal change, such as shoreline change. The area between Cape Canaveral and the false cape to the north is experiencing long-term shoreline loss of 1 to 2 m per year (fig. 3), narrowing the beach, and increasing vulnerability to storms. NACCH surveyed the nearshore bathymetry of KSC and CCAFS in August 2014 using topo- bathymetric lidar and single-beam sonar (Thompson et. al, 2015). Comparisons between National Oceanic and Atmospheric Administration (NOAA) National Ocean Service (NOS) bathymetry collected in 1956 and bathymetry from 2014 show deepening offshore of the mid- Cape region (fig. 4). This change in bathymetry allows larger waves to impact the shoreline, increasing the vulnerability of the coastline to erosion and overwash. KSC and CCAFS face challenging coastal management decisions, such as protecting valuable infrastructure from storms and sea-level rise while maintaining critical habitats for sea turtles. NACCH data and analyses have provided scientific tools for decision-makers as they manage over 30 km of KSC and CCAFS coastline. The USGS Coastal Change Hazards Portal provides online interactive access to data and products such as rates of long-term shoreline change, and vulnerability to coastal hazards such as storms and sea-level rise. Figure 3. This image from the USGS Coastal Change Hazards Portal illustrates long-term rates of shoreline change for open-ocean shorelines at Cape Canaveral. While the overall shoreline change rate for KSC and CCAFS is near zero, long-term shoreline retreat of 1 to 2 m/yr can be seen in the area between Cape Canaveral and the false cape. Figure 4. (A) Gridded 1956 data from NOAA NOS bathymetric survey. (B) Long-term bathymetric change (1956 to 2014) shows deepening offshore of the mid-cape region. (C) NACCH gridded 2014 integrated sonar and lidar data. Figure from Thompson et. al, 2015. References Thompson, D. M., N. G. Plant, M. E. Hansen, and D. M. Thompson, Plant, N.G., and Hansen, M.E., 2015, Analysis of bathymetric surveys to identify coastal vulnerabilities at Cape Canaveral, Florida: U.S. Geological Survey Open–File Report 2015–1180, 24 p., http://dx.doi.org/10.3133/ofr20151180 For more information contact: Hilary Stockdon, Project Lead USGS St. Petersburg Coastal and marine Science Center 600 4th Street South St. Petersburg, FL 33701 Phone: 727-502-8074 Email: [email protected] Website: http://coastal.er.usgs.gov/hurricanes/ .