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Coastal Bluffs 1:24,000-scale Maps Digital Data
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Data Description and Usage
This dataset contains line data describing the shoreline type and relative stability of bluffs along a section of the Maine coast mapped at a scale of 1:24,000. A bluff is defined as a steep shoreline slope formed in sediment (loose material such as clay, sand, and gravel) that has three feet or more of vertical elevation just above the high tide line. In 2026, the Maine Geological Survey updated the Casco Bay portion of this dataset to include new factors associated with bluff stability and sediment supply from coastal bluffs to the coastal wetland and a summary of mapped adjacent habitats. Further updates covering the rest of the Maine coast will be completed by 2029. The Maine Geological Survey uses this dataset to produce Coastal Bluffs Maps.
- Shoreline segments are classified in the BLUFF field as either being bluff (Y), non-bluff (N), or unmapped or undetermined (X).
- The relative stability of a bluff face is classified in the STABILITY field as being either not a bluff (N), stable (S), unstable (U), highly unstable (H), or unmapped or undetermined (X). This classification is based on observed factors that reflect recent activity on the bluff face. Ratings for these individual observed factors are also provided where data have been updated (areas without an update will show blank values). Refer below for a table describing these factors.
- The shoreline type is classified in the TYPE field as either ledge (exposed bedrock outcrops) (L), armored (seawall, riprap, gabion, bulkhead, etc.) (A), salt marsh (V), beach, mud flat, or other loose sediment (N), or unmapped or undetermined (X). Multiple shoreline types may co-exist on any given section of coastline (example, TYPE L-V indicates, landward to seaward, presence of ledge and vegetation).
- Where data have been updated since 2026:
- Maine Geological Survey has added several new variables indicating visual and terrain characteristics of stability. See the field table below for more information.
- Sediment supply is classified in the Sediment_Value field with ratings of None, Low, Medium, or High. Areas without an update will have a blank value. The classification is based on observed evidence of erosion and sediment transport from coastal bluffs to the coastal wetland.
- The map now documents the adjacency of coastal bluffs to special mapped habitats and a total count of these habitats. See the field table below for more information.
Data Disclaimer
This digital resource may not include information from the most recently published coastal bluffs maps. This data will be updated on a seasonal/quarterly basis but may be out of step briefly with published maps. The user should check the source attributes associated with the coastal bluffs data lines and verify that the digital data reflects the current published map for the quadrangle. The user can view the most recently published maps or check the source for the cited open-file map in the Maps and Publications Search by searching for the open-file number (e.g. 04-93) in the publication number field.
These data are meant to help inform decisions at the local, regional, and state-level. Users must assume responsibility in determining the usability of this data for their purposes. Metadata is included for all of the downloadable layers and should be reviewed for more specifics on how these data were created. Neither the Maine Geological Survey nor the Department of Agriculture, Conservation and Forestry, nor its employees or agents: (1) make any warranty, either expressed or implied for merchantability or fitness for a particular purpose, as to the accuracy or reliability of the information shown on the map; nor are they (2) liable for any damages, including consequential damages, from using the map or the inability to use the map.
Online Maps
Digital Data
What's New in 2026
Maine Geological Survey has updated coastal bluff stability, sediment, and habitat ratings for Casco Bay. Further updates covering the rest of the Maine coast are planned through 2029. The following detailed information is used as the basis of the updated stability ratings and will also be included in the map as updates proceed (locations without these updates will show a blank value):
| Field name | Field name alias | Description | Criteria/Domain | Source | Used for rating |
|---|---|---|---|---|---|
| BLUFF | Used to classify whether shoreline segment is coastal bluff (Y) or not (N), or if the segment is unmapped (X). | Y, N, X | MGS | Not used for any rating | |
| STABILITY | Stability rating for bluffs: Stable (S), Unstable (U), Highlt unstable (H), or if the segment is not characterized as a bluff (N) or unmapped (X). | S, U, H, N, X | MGS | Product of rating | |
| TYPE | Type of coastal habitat present seaward of the shoreline segment: Ledge (L), Armor (A), Vegetation (V), beach, sand flat, or mudflat (N). | L, A, V, N, or combinations of three | MGS | Sediment value | |
| Sediment_Value | Sediment Score | Total rating based on sediment factors. | None, Low, Medium, High | MGS | Product of sediment rating |
| Sediment_Score | Sediment Numeric Score | Sum of points used to determine sediment score. | Integer | MGS | Product of sediment rating |
| COMMENTS | Comments provided by MGS during mapping update process. | Text | MGS | Not used for any rating | |
| QUADNAME | Name of quadrangle map in which the bluff segment is located. | Text | MGS | Not used for any rating | |
| ASSESSMENT_DATE | Only used for field site visits - date of latest field assessment of bluff segment. | Date | MGS | Not used for any rating | |
| ToeErosion | Toe erosion | Presence of steep, exposed sediments indicating scarping and erosion at the base or toe of the bluff. | None, minimal, moderate, extensive | Oblique aerial imagery, field verification | Stability, sediment value |
| ExposedSedimentOnSlopes | Exposed sediment on slopes | Presence of exposed sediments anywhere on the bluff slope indicating loss or erosion of protective vegetation. | None, minimal, moderate, extensive | Oblique aerial imagery, field verification | Stability, sediment value |
| LandslidesOrSlumps | Landslides or slumps | Presence of slump/slide textures on exposed bluff sediments and sediment or vegetation collected at the toe of the bluff as loose blocks, colluvium, or liquefaction. | None, minimal, moderate, extensive | Oblique aerial imagery, field verification | Stability, sediment value |
| FallenTrees | Fallen trees | Presence of fallen or heavily leaning trees on the bluff. | None, minimal, moderate, extensive | Oblique aerial imagery, field verification | Stability |
| GroundwaterOrRunoff | Evidence of groundwater and/or runoff | Presence of wet or seeping exposed sediments with scalloping failure or subsidence on the bluff, channels/runnels incising the bluff, pooling above the bluff, occurrence of poor land use practices encouraging runoff or groundwater seepage through the bluff, presence of suspended sediment plumes in the intertidal area seaward of the bluff, and/or presence of freshwater plants at the toe of the bluff. | None, minimal, moderate, extensive | Oblique aerial imagery, field verification | Stability |
| FailedArmor | Failed armor | Presence of armor with visible damage: undercut or tilting seawalls, broken/cracked seawalls, settling, slumping, or scattering of rip-rap, erosion behind/landward of the armor, eroded and exposed underlayment. | None, minimal, moderate, extensive | Oblique aerial imagery, field verification | Stability |
| SedimentTransport | Noted evidence of sediment transport | Relative abundance of sediment adjacent to a bluff exhibiting erosion in the form of wide beaches, expansive mudflats/sandflats, fringe marshes, and sand/cobble dunes. | None, minimal, moderate, extensive | Oblique aerial imagery, field verification | Sediment value |
| Aspect | Aspect | Orientation of the bluff face reported by compass direction. Important for determining effects of spring freeze-thaw cycles on stability for south-facing bluffs. | S, SE, SW; E, W; NE, NW; N | NOAA Maine 2022-2023 topobathy lidar | Stability |
| Height | Height | Height of the bluff reported in feet, measured as the amount of relief between the highest astronomical tide elevation and the elevation at hte top of the bluff. | 0-5 ft, 5-10 ft, 10-20 ft, >20 ft | NOAA Maine 2022-2023 topobathy lidar | Stability, sediment value |
| Slope | Slope | Slope of the bluff reported in percent grade. | 0-25%, 26-50%, 51-75%, 76-100%, >100% | NOAA Maine 2022-2023 topobathy lidar | Stability |
| Armored | Armor type | If armor is present, report the most prominent type: vertical bulkhead or rip-rap. | None, vertical bulkhead, rip-rap | Oblique aerial imagery, field verification | Not used for any rating |
| SpecialHabitatType_SandDune | Sand Dune Habitat | Presence of coastal sand dunes within 328 feet of shoreline segment. | Yes, No | MGS | Habitat count |
| SpecialHabitatType_TWWH | TWWH Habitat | Presence of tidal waterfowl and wading bird habitat within 328 ft of shoreline segment. | Yes, No | DIFW | Habitat count |
| SpecialHabitatType_Eelgrass | Seagrass Habitat | Presence of seagrass habitat within 328 ft of shoreline segment. | Yes, No | DEP | Habitat count |
| SpecialHabitatType_Shellfish | Shellfish Habitat | Presence of shellfish beds within 328 ft of shoreline segment. | Yes, No | DMR | Habitat count |
| SpecialHabitatType_MarineWorm | Marine Worm Habitat | Presence of marine worm beds within 328 ft of shoreline segment. | Yes, No | DMR | Habitat count |
| Landcover | Dominant Landcover Type | Majority land cover class found within 100 ft of shoreline segment. Classes have been condensed form original classes reported by NOAA C-CAP program. | Omit (no data), Developed, Cultivated, Pasture/grassland, Forest, Scrub/shrub, Wetland, Bare land | NOAA C-CAP Landcover | Not used for any rating |
| Score | Stability Numeric Score | Numeric score for bluff stability, values exist only for bluffs remapped prior to 2025, refer to feature layer summary for a description of the scoring method. | Integer | MGS | Product of stability rating |
| SpecialHabitatType_EssHabitat | Essential Habitat | Yes, No | DIFW | Habitat count | |
| SpecialHabitatType_ETSC | ETSC Habitat | Areas identified as potential habitat for endangered, threatened, or special concern species within 328 ft of shoreline segment. | Yes, No | DIFW | Habitat count |
| Slope_Bathy | Bathymetric slope | Average slope within 100 ft seaward of the highest astronomical tide line derived from bathymetric lidar. | Numeric | NOAA Maine 2022-2023 topobathy lidar | Not used for any rating |
| Relief_Bathy | Bathymetric relief | Greatest relief within 100 ft seaward of the highest astronomical tide line derived from bathymetric lidar. | Numeric | NOAA Maine 2022-2023 topobathy lidar | Not used for any rating |
| CMGE_Subtidal | CMGE Subtidal Habitat | Text descriptions of adjacent Coastal Marine Geologic Environment habitat classes in the subtidal area within 328 ft of bluffs. | Text | MGS CMGE | Not used for any rating |
| CMGE_Intertidal | CMGE Intertidal Habitat | Text descriptions of adjacent Coastal Marine Geologic Environment habitat classes in the intertidal area within 65 ft of bluffs. | Text | MGS CMGE | Not used for any rating |
| CMGE_Supratidal | CMGE Supratidal Habitat | Text descriptions of adjacent Coastal Marine Geologic Environment habitat classes in the supratidal (above highest astronomical tide) area within 165 ft of bluffs. | Text | MGS CMGE | Not used for any rating |
| ESIL_Seaward | ESIL Seaward Habitat | Text descriptions of adjacent Environmental Sensitivity Index seaward habitat classes within Xft of the shoreline segment. | Text | NOAA | Not used for any rating |
| ESIL_Landward | ESIL Landward Habitat | Text descriptions of adjacent Environmental Sensitivity Index landward habitat classes within Xft of the shoreline segment. | Text | NOAA | Not used for any rating |
| CBEP_FringingMarsh | CBEP Fringing Marsh | Presence of fringing marsh based on assessments completed for Casco Bay Estuary Partnership | Yes, No | CBEP, NOAA | Habitat count |
| Wave_Energy | Wave Energy | Wave energy (Joules per meter squared) projection for shoreline segment based on sampling of NOAA Coastal Ocean Reanalysis (CORA) during storm time periods. | Very low energy (<5), Low energy (5-50), Moderate energy (50-200), High energy (200-600), Very high energy (>600) | NOAA CORA, UMaine Engineering | Not used for any rating |
| Confidence | Score Confidence | Level of confidence reported by the mapper based on availability of data. | High, confirmed in field; High, confirmed with imagery; Moderate, confirmed with terrain data and limited imagery; Low, confirmed with terrain data, poor or absent imagery | MGS | Not used for any rating |
| Habitat_Count | Adjacent Habitat Count | Sum of adjacent special mapped habitats. | Integer | MGS | Product of habitat count |
| SpecialHabitatType_ShrbrdArea | Shorebird Habitat | Shorebird feeding and roosting areas that qualify as Significant Wildlife Habitat under Maine's Natural Resources Protection Act within 328 ft of shoreline segment. | Yes, No | DIFW | Habitat count |
| Change_in_Stability | Change in Stability | Change in stability rating since last large-scale bluff map publication (2025) | Text | MGS Coastal Bluffs Archive | Not used for any rating |
| SegmentID | SegmentID | Unique ID value for each shoreline segment. | Integer | MGS | Not used for any rating |