COASTAL BLUFF HAZARDS

                                The data were compiled on a 1:24,000 scale base with a horizontal accuracy +/- 40 feet or 12 meters.
                              

                                USGS 1:24,000 7.5' quadrangles used as mapping base
                              

                                Data, from the Maine Office of Geographic Information Systems (MEGIS) 1:24000 library layer COAST represents the Mean High Water (MHW) line, tidal rivers and salt water ponds of coastal Maine.
                              

                                Geologists classified the coastal bluffs in this data set by observing the shoreline from small boats.  Segments of the coast were coded as to shoreline type and stability on paper copies of quadrangle maps, and the data transferred to a digital coverage of the coastline, splitting and coding arc segments as needed.

The geologists then assigned one of the following categories to the type of shoreline seen below the high tide line: (1) ledge (exposed bedrock outcrops); (2) armored (seawall, riprap, gabion, bulkhead, etc.); (3) salt marsh; or (4) beach, mud flat, or other loose sediment.  The data set includes the shoreline type, including segments of the shoreline without significant coastal bluffs.  Where significant bluffs were present, geologists noted various characteristics of the bluff face such as the slope of the bluff (steep to gentle), features on the bluff face indicating recent movement of material down the slope (slumped blocks of sediment, landslide scars, fallen trees), and the amount and type of vegetation (bare sediment, grass, shrubs, mature trees).  From this information, geologists assessed the relative stability of each bluff face as being  (1) stable, (2) unstable, or (3) highly unstable.  This classification is based on observed features that reflect recent activity on the bluff face.

Landslide sites (LANDSLIDE = 'R', HAZARD = 'RPH')  identified by the following:  (1) Locations based on historical records and eyewitness accounts.  In general, these earth movements have occurred in the last three centuries.  (2) Locations based on interpretation of aerial photography.

Landslide risk areas (LANDSLIDE = 'Y', HAZARD = 'RF') identified by the following:  (1) Observations from land corroborated with geomorphology observed on air photos, sediment types shown on surficial geologic maps, and both elevation above sea level and steepness of bluff slopes shown on topographic maps.  Bluff sediments are usually muddy and twenty feet or more in thickness.  The slope on the bluff face appears steep and similar to areas where there have been landslides in the past.  (2) Observations from a small boat.  Primarily steeply-sloping sediment bluffs that were visually estimated to be twenty feet or more in elevation.  Other instability characteristics included unvegetated slopes on the bluff face; leaning, fallen, or crooked tree trunks; and visible slump deposits at the base of the bluff near the high-tide line.  The site may be adjacent to previous landslides.  In this second category, aerial photographs were not used nor were the surficial geologic materials investigated.

Potential landslide area (LANDSLIDE = 'R' HAZARD = 'RA') was based on the presence of a bluff as indicated on MGS coastal bluff maps (coastal bluffs data set), the proximity of a twenty-foot topographic contour to the shoreline (similar to areas adjacent to previous landslides) and geomorphology visible in air photos.  These bluff areas have not had field investigations to fully evaluate landslide risk.
                              

                                Replaced arcs for the following Maine Geological Survey publications:
05-19 Coastal bluffs in the Bass Harbor quadrangle, Maine (superseded publication 03-10)
05-21 Coastal bluffs in the Seal Harbor quadrangle, Maine (superseded publication 03-6)
05-22 Coastal bluffs in the Southwest Harbor quadrangle, Maine (superseded publication 03-26)
05-41 Coastal bluffs in the Hancock quadrangle, Maine (superseded publication 03-12)
05-42 Coastal bluffs in the Sullivan quadrangle, Maine (superseded publication 02-216)
06-63 Coastal bluffs in the Harrington quadrangle, Maine (superseded publication 04-22)
06-66 Coastal bluffs in the Winter Harbor quadrangle, Maine (superseded publication 04-26)
06-70 Coastal bluffs in the Bar Harbor quadrangle, Maine (superseded publication 02-170)
and
05-24 Coastal landslide hazards in the Hancock quadrangle, Maine (superseded publication 03-13)
05-32 Coastal landslide hazards in the Bass Harbor quadrangle, Maine (superseded publication 03-11)
05-34 Coastal landslide hazards in the Seal Harbor quadrangle, Maine (superseded publication 03-7)
05-35 Coastal landslide hazards in the Southwest Harbor quadrangle, Maine (superseded publication 03-25)
05-37 Coastal landslide hazards in the Sullivan quadrangle, Maine (superseded publication 01-545)
06-67 Coastal landslide hazards in the Winter Harbor quadrangle, Maine (superseded publication 04-27)
06-71 Coastal landslide hazards in the Bar Harbor quadrangle, Maine (superseded publication 01-499)
 
Added arcs for the following Maine Geological Survey publications:
05-47 Coastal bluffs in the Baker Island quadrangle, Maine
06-55 Coastal bluffs in the Wells quadrangle, Maine
06-57 Coastal bluffs in the Kennebunkport quadrangle, Maine
06-59 Coastal bluffs in the York Beach quadrangle, Maine
06-61 Coastal bluffs in the Addison quadrangle, Maine
06-64 Coastal bluffs in the Drisko Island quadrangle, Maine
06-68 Coastal bluffs in the Schoodic Head quadrangle, Maine
and
05-31 Coastal landslide hazards in the Baker Island quadrangle, Maine
06-56 Coastal landslide hazards in the Wells quadrangle, Maine
06-58 Coastal landslide hazards in the Kennebunkport quadrangle, Maine
06-60 Coastal landslide hazards in the York Beach quadrangle, Maine
06-62 Coastal landslide hazards in the Addison quadrangle, Maine
06-65 Coastal landslide hazards in the Drisko Island quadrangle, Maine
06-69 Coastal landslide hazards in the Schoodic Head quadrangle, Maine
                              

                                Updated/replaced bluff/landslide arcs for the following MGS publications:
08-63, Coastal bluffs in the Pemaquid Point quadrangle, Maine (supersedes 02-202).
08-40, Coastal landslide hazards in the Pemaquid Point quadrangle, Maine (supersedes 01-531).
                              

                                Metadata imported.
                              

                                Dataset copied.
                              

                                Dataset copied.