Emily A. Himmelstoss

Bluff Evolution along Coastal Drumlins: Boston Harbor Islands, Massachusetts

Abstract A series of partially drowned drumlins forms the backbone of the inner islands within Boston Harbor. The shoreline of these rounded glacial deposits is composed of actively retreating bluffs formed by continual wave attack. Comparisons of bluffs reveal variability in their height and lateral extent, as well as in the dominant mechanism causing their retreat. Two processes are responsible for bluff erosion and yield distinct bluff morphologies: (1) wave attack undercuts the bluff and causes episodic slumping, yielding planar bluff slopes, and (2) subaerial processes such as rainfall create irregular slopes characterized by rills and gullies. We propose a model of drumlin bluff evolution that is based on processes of erosion and physical characteristics such as bluff height, slope morphology, and the orientation of the bluff with respect to the long axis of the drumlin and its topographic crest. The four phases of drumlin bluff evolution consist of (1) initial formation of bluff, with retreat dominated by wave notching and slumping processes; (2) rill and gully development as bluff heights exceed 10 m and slumped sediment at bluff base inhibits wave attack; (3) return of wave notching and slumping as bluff heights decrease; and (4) final development of boulder retreat lag as last remnants of drumlin are eroded by wave action. These phases capture the important physical processes of drumlin evolution in Boston Harbor and could apply to other eroding coastal drumlin deposits.

National Assessment of Shoreline Change: A GIS compilation of Updated Vector Shorelines and Associated Shoreline Change Data for the Southeast Atlantic Coast

Sandy ocean beaches in the United States are popular tourist and recreational destinations and constitute some of the most valuable real estate in the country. The boundary between land and water along the coastline is often the location of concentrated residential and commercial development and is frequently exposed to a range of natural hazards, which include flooding, storm effects, and coastal erosion. In response, the U.S. Geological Survey (USGS) is conducting a national assessment of coastal change hazards. One component of this research effort, the National Assessment of Shoreline Change Project, documents changes in shoreline position as a proxy for coastal change. Shoreline position is an easily understood feature representing the historical location of a beach position through time. This report is an update to the original Southeast Atlantic (Morton and Miller, 2005) assessment and includes revised rate-of-change calculations based on additional shoreline position data, improved rate metrics, and application of a proxy-datum bias correction that quantifies potential bias and errors associated with integrating shorelines referenced to different proxies. To be consistent with previous work, the Southeast Atlantic study areas were organized by state for analysis.

Baseline coastal oblique aerial photographs collected from Owls Head, Maine, to the Virginia/North Carolina border, May 19-22, 2009

The U.S. Geological Survey (USGS) conducts baseline and storm response photography missions to document and understand the changes in vulnerability of the Nations coasts to extreme storms. On May 19-22, 2009, the USGS conducted an oblique aerial photographic survey from Owls Head, Maine, to the Virginia/North Carolina border, aboard a Cessna 207A aircraft at an altitude of 500 feet (ft) and approximately 1,200 ft offshore (Figure 2, http://pubs.usgs.gov/ds/0946/html/ds946_fig2.html). This mission was flown to collect data for assessing incremental changes since the last survey, flown October 2000, and can be used for assessing future coastal change. The photographs provided here are Joint Photographic Experts Group (JPEG) images. The photograph locations are an estimate of the position of the aircraft and do not indicate the location of the feature in the images. (See the Navigation Data page in the corresponding report, for additional details, http://pubs.usgs.gov/ds/0946/html/ds946_nav.html). These photographs document the configuration of the barrier islands and other coastal features at the time of the survey. ExifTool (http://www.sno.phy.queensu.ca/~phil/exiftool/) is a free software program for reading, writing, and manipulating image, audio, and video metadata. ExifTool was used to add the following to the header of each photo: time of collection, Global Positioning System (GPS) latitude, GPS longitude, keywords, credit, artist (photographer), caption, copyright, and contact information. Photographs can be opened directly with any JPEG-compatible image viewer by clicking on a thumbnail on the contact sheet. All image times are recorded in UTC. Table 1 (http://pubs.usgs.gov/ds/0946/html/ds946_table.html) provides detailed information about the assigned location, name, date, and time the photograph was taken along with links to the photograph. In addition to the photographs, a Google Earth Keyhole Markup Language (KML) file is provided and can be used to view the images by clicking on the marker and then clicking on either the thumbnail or the link above the thumbnail. The KML files were created using the photographic navigation files. Note: A KML number was assigned to each photograph to aid navigation of the Google Earth file. These numbers correspond to the site labels in Google Earth.