In the summer of 2023, Whiteout Solutions began conducting a high-resolution aerial LiDAR and Imagery survey of all the protected coastal marshland and 100-foot upland buffers across the state of Connecticut. The purpose of this work is to establish a baseline dataset for each of these sites which can be used for planning, designing and conservation efforts today or compared against when future data collection efforts occur. The project produced several different deliverables, the primary being elevation and imagery, as well as secondary deliverables including a vegetation landcover classification.
As a part of the project , Whiteout Solutions is sharing the data products through an interactive web application called geoSAP that includes all datasets and derivatives for over 200 sites across Connecticut. All data layers can be viewed and downloaded through geoSAP.
The project was lead by CT DEEP with funding from the Long Island Sound Study.
Data Layer Information
LiDAR (Elevation) Data Layers
LiDAR Layers
Lidar is a remote sensing technology that uses laser pulses to collect points that together create high-resolution, 3D representations of the Earth's surface and features. Each lidar point has an elevation. The lidar points, called a point cloud, can be converted to other formats that are pixels instead of points and are easier to work with.
To view any of the lidar products, use geoSAP. Once downloaded, these file types require GIS or remote sensing software or similar.
Classified Point Cloud (*.las)(*.laz). The lidar point cloud where each point is identified to belong to a class. The classes follow ASPRS standards and are (1) unassigned, (2) ground, (3) low vegetation, (4) high vegetation, (17) bridge deck, (18) water surface.
Digital Surface Model (DSM) (*.tif). The DSM is a raster dataset where each pixel has the elevation of the surface, or highest point returned. The DSM measures the top of vegetation and other features.
Digital Terrain Model (DTM) (*.tif). The Digital Terrain Model is also called a DEM which stands for Digital Elevation Model. The DTM is a raster dataset where each pixel has the elevation of the bare earth ground below any vegetation.
Elevation Contour (*.shp/*.gsvec). Contour lines connect points of the same elevation. In this project, each line has a 1 foot difference in elevation.
Imagery Data Layers
Imagery Layers
Color imagery is captured using a minimum of 3 bands, usually red, green, and blue (RGB). Although the imagery collected for the project has many more bands, the "true color" aerial in the viewer is displaying RGB. Orthomosaic means that the imagery has been corrected for elevation variation so that it can be used for accurate measurements.
Image sensors are engineered to capture reflectance at different wavelengths of light. A single band collects a specific range of wavelengths. Different wavelengths can be compared to reveal features on the land, often called a derived index. Here, 5 indices were created from the aerial imagery and are included in the viewer.
RGB Orthomosaic (*.tif). Aerial imagery shown as true color.
Derived Indices
NDVI (*.tif). The Normalized Difference Vegetation Index measures vegetation health where high values are healthier vegetation.
NDRE (*.tif). The Normalized Difference Red Edge Index monitors chlorophyll content and vegetation stress.
NDBSI (*.tif). The Normalized Difference Bare Soil Index identifies areas of bare soil.
NDWI (*.tif). The Normalized Difference Water Index assesses water content in vegetation along with water bodies.
RTVIcore (*.tif). The Red-Edge Triangulated Vegetation Index estimates leaf area index and biomass.
Derived Data Layers
Additional Derived Layers
The elevation and imagery layers were used with specialized software and methods to create a highly-detailed vegetation classification for Connecticut marshes. The landcover is a representation of the seven primary marsh vegetation types in Connecticut.
Vegetation Land Cover Classification. Vegetation classes include
| Asphalt | Mudflat | ||
| Boat | Other Vegetation | ||
| Building | Pebbles, Gravel, Small Rocks | ||
| Coniferous | Phragmites australis | ||
| Dead Phragmites australis | Sand | ||
| Deciduous | Spartina alterniflora (short form) | ||
| Dirt | Spartina alterniflora (long form) | ||
| Distichlis spicata | Spartina patens | ||
| Dock | Unknown Structure | ||
| Grass Lawn | Water | ||
| Mixed Forest | unclassified |
During 2021, Whiteout Solutions, LLC conducted a series of drone flights to collect remotely-sensed elevation and landcover data at five tidal marshes in Connecticut, USAPilots flew drones at all sites to collect RGB imagery, multispectral imagery, high density return LiDAR, and thermal imagery. Two flights were conducted at each site, one at low tide (July 13th or 14th) and one at high tide (August 16th, 17th, or 18th).
Background and Purpose
Background
Tidal marshes worldwide [1], and in coastal New England [2], are rapidly declining. Major causes of tidal marsh loss include sea level rise and reduced sediment in the water [3], and tidal marsh declines are often punctuated by losses in elevation relative to sea level (marsh ‘drowning’). Species that rely on tidal marsh habitat are therefore threatened by this ecosystem degradation and understanding how species respond both to ongoing degradation and to restoration efforts designed to reverse the losses, is key to their persistence.
Bird species such as saltmarsh sparrow and clapper rail are already declining, and declines of other species are expected as marshes flood more frequently and marsh vegetation changes. Because habitat transitions occur along a very shallow elevation gradient in tidal marshes, and because sea level rise is predicted to occur at rates of ~3 mm per year in coastal New England [4], elevation data needs to be of high precision to understand how future sea level conditions may alter the plant communities of tidal marshes, and the animals that depend on them.
Implications
The areas flown at Great Meadows Marsh, Sluice Creek, and Bride Brook contain patches of degraded tidal marsh where there are plans for marsh restoration through the addition of a thin layer placement of sediment. These flights therefore serve as pre-management data collection efforts. The areas flown at Hammonasset Beach State Park and Barn Island Wildlife Management Area include patches of habitat that have been surveyed for the tidal marsh breeding birds since 2002. These flights therefore serve as benchmark data collection efforts to relate future changes in habitat composition to future changes in saltmarsh bird populations at each site.
Purpose
Data collected during these drone flights will be used to understand how habitat changes manifest in Connecticut’s tidal marshes as sea levels continue to rise. These data will also be used to inform our understanding of the fine scale elevation and habitat responses following restoration activities that use thin-layer sediment placement. The dataset provides elevation data for sections of five tidal marshes through a variety of remote sensing products including point cloud, DEM, and DSM products. It also contains thermal imagery data and multispectral imagery, which can be used to estimate aboveground plant species composition and biomass. These data will be valuable to all individuals interested in tidal marsh elevation, landcover, or future changes in coastal Connecticut.
Literature Cited
1. C. J. Mcowen et al., A global map of saltmarshes. Biodiversity Data Journal e11764 (2017).
2. E. B. Watson et al., Anthropocene survival of southern New England’s salt marshes. Estuaries Coast 40, 617–625 (2017).
3. S. Fagherazzi, et al., Numerical models of salt marsh evolution: Ecological, geomorphic, and climatic factors. Reviews of Geophysics 50 (2012).
4. J. A. Church, N. J. White, Sea-level rise from the late 19th to the early 21st century. Surveys in Geophysics 32, 585–602 (2011).
Study Sites
Barn Island Wildlife Management Area, Stonington
Bride Brook, Rocky Neck State Park, East Lyme
Hammonasset Beach State Park, Madison
Sluice Creek, Guilford
Great Meadows, Stewart B. McKinney National Wildlife Refuge, Stratford
Download and Connect
| Site | Dataset Date | Format | Download Link and File Size |
| Barn Island | August 17, 2021 | tif | download zip 1 (617 MB) download zip 2 (1.6 GB) |
| Bride Brook | August 17, 2021 | tif | download zip (349Mb) |
| Hammonasset | July 13, 2021 | tif | download zip (749Mb) |
| Sluice Creek | August 18, 2021 | tif | download zip (851Mb) |
| Stratford Great Meadows | August 18, 2021 | tif | download zip (2.2Gb) |
Layer Name:
Orthomosaics
| Site | Dataset Date | Format | Download Link and File Size |
| Barn Island (eastern section) | August 17, 2021 | tif | section 1 - download zip (617Mb) |
| Barn Island (western section) | August 17, 2021 | tif | section 2 - download zip (1.6Gb) |
| Bride Brook | August 17, 2021 | tif | download zip (879Mb) |
| Hammonasset | July 13, 2021 | tif | download zip (551Mb) |
| Hammonasset | August 16, 2021 | tif | download zip (2.2Gb) |
| Sluice Creek | August 18, 2021 | tif | download zip (1.9Gb) |
| Stratford Great Meadows | August 18, 2021 | tif | download zip (4.32Gb) |
Layer Name:
Aerial_5band
| Site | Dataset Date | Format | Download Link and File Size |
| Barn Island | August 17, 2021 | tif | download zip (178Mb) |
| Barn Island | August 17, 2021 | kml | download (1kb) |
| Barn Island | August 17, 2021 | asc | download zip (108Mb) |
| Bride Brook | August 17, 2021 | tif | download zip (18Mb) |
| Bride Brook | August 17, 2021 | kml | download (1kb) |
| Bride Brook | August 17, 2021 | asc | download zip (19Mb) |
| Hammonasset | July 13, 2021 | tif | download zip (61Mb) |
| Hammonasset | July 13, 2021 | kml | download (1kb) |
| Hammonasset | July 13, 2021 | asc | download zip (58Mb) |
| Hammonasset | August 16, 2021 | tif | download zip (61Mb) |
| Hammonasset | August 16, 2021 | kml | download (1kb) |
| Hammonasset | August 16, 2021 | asc | download zip (57Mb) |
| Sluice Creek | August 18, 2021 | tif | download zip (38Mb) |
| Stratford Great Meadows | August 18, 2021 | tif | download zip (69Mb) |
Layer Name:
Marshes_DSM
| Site | Dataset Date | Format | Download Link and File Size |
| Barn Island | August 17, 2021 | tif | download zip (167Mb) |
| Barn Island | August 17, 2021 | kml | download (1kb) |
| Barn Island | August 17, 2021 | asc | download zip (100Mb) |
| Bride Brook | August 17, 2021 | tif | download zip (16Mb) |
| Bride Brook | August 17, 2021 | kml | download (1kb) |
| Bride Brook | August 17, 2021 | asc | download zip (17Mb) |
| Hammonasset | July 13, 2021 | tif | download zip (57Mb) |
| Hammonasset | July 13, 2021 | kml | download (1kb) |
| Hammonasset | July 13, 2021 | asc | download zip (55Mb) |
| Hammonasset | August 16, 2021 | tif | download zip (56Mb) |
| Hammonasset | August 16, 2021 | kml | download (1kb) |
| Hammonasset | August 16, 2021 | asc | download zip (53Mb) |
| Sluice Creek | August 18, 2021 | tif | download zip (34Mb) |
| Stratford Great Meadows | August 18, 2021 | tif | download zip (61Mb) |
Layer Name:
Marshes_DTM