3 Statutory Definitions
C.G.S. Sec. 8-13aa defines developable land and what is not considered to be within the context of this planning process:
(5) “Developable land” means land, including any land owned by the state or a political subdivision of the state, including a municipality, that, as of January 1, 2026, can be feasibly developed or redeveloped into a residential development or a mixed-use development, as defined in section 8-13m of the general statutes, provided the feasibility of such development or redevelopment is based on commercially reasonable assumptions. “Developable land” does not include: (A) Land already committed to a public use or purpose, whether publicly or privately owned; (B) open space, parks and recreation areas that are dedicated to the public or subject to a recorded conservation easement; (C) land that is subject to an enforceable restriction on or prohibition of development, provided any such restriction or prohibition is not imposed by any zoning regulations or ordinance adopted by a municipality; (D) wetlands or watercourses, as defined in chapter 440 of the general statutes; and (E) areas of one-half or more acres of contiguous land that are unsuitable for development due to topographic features, such as steep slopes;
This developable land inventory is intended as a high-level GIS screening tool to support the preparation of Housing Growth Plans. The inventory applies the definition in C.G.S. Sec. 8-13aa and provides a framework for identifying land that should be evaluated further through local planning and feasibility analysis. The inventory and associated GIS screening methodology are not intended to serve as a final determination of whether individual areas or parcels are developable or redevelopable.
Commercially reasonable assumptions: The statute requires that feasibility determinations for developable land be grounded in commercially reasonable assumptions. This standard is inherently context dependent. What counts as a commercially reasonable assumption in one municipality or region may not hold true in another, given differences in market conditions, infrastructure capacity, land values, and local development patterns. Because of this variability, this guidance does not attempt to define a single statewide threshold for what makes an assumption commercially reasonable. The methods outlined to identify vacant and land for potential redevelopment in Section 4 could provide a starting point for this analysis. Municipalities and COGs should apply local market knowledge and professional judgment when assessing feasibility, consistent with the statutory standard.
The GIS methodology described in this guidance focuses on identifying land that is statutorily excluded from further developability analysis. Land that is not excluded should not automatically be interpreted as developable. Rather, it represents land that may warrant additional evaluation during preparation of the Regional Needs Assessment and Housing Growth Plans using locally informed, commercially reasonable assumptions.
Under the statute, several types of land are defined as areas that should be excluded from these developable land inventories:
- Land already committed to public use or purpose (public or private)
- Open space, parks, and recreation areas dedicated to the public or protected by a conservation easement
- Land subject to enforceable restrictions or prohibitions on development
- Wetlands or watercourses, as defined in the Wetlands and Watercourses Act (C.G.S. Chapter 440)
- Contiguous land areas of 0.5 acres or more that are unsuitable for development due to steep slopes or other topographic conditions
In addition to incorporating these categories, the final inventory may also document vacant land and land with potential for redevelopment. These areas provide important context for the development of other elements of the Housing Growth Plans, in which suitability analyses may be used to complete a more detailed assessment on capacity for future housing growth. Suggestions for identifying and analyzing vacant and potentially redevelopable land are provided in Section 4.
The sections below describe each statutory exclusion category, identify potential datasets for GIS analysis, and provide technical guidance for preparing those datasets. These procedures are intended to support consistent statewide screening and mapping of statutory exclusions. They are not intended to replace the detailed municipal and regional analysis required to determine whether land ultimately meets the statutory definition of developable land.
Workflow Overview
For each statutory exclusion category, the workflow will generally proceed as follows:
- Identify datasets that capture relevant land, parcel, or resource information associated with each category.
- Filter datasets to the regional study area (i.e. municipality or planning region) and, where necessary, apply attribute queries or other selection criteria to isolate relevant features.
- Review and verify selected areas for accuracy using available reference materials, including aerial imagery, local knowledge, municipal mapping resources, and other supporting datasets.
Finally, the land areas for each category would be compiled and symbolized in accordance with the mapping standards described in Section 5. The final maps layouts include the land area identified in this section. Inventories are recommended to include vacant land from Section 4.1 and land for potential redevelopment from Section 4.2, since these components will be used in subsequent phases of the analyses.
3.1 Land already committed to public use or purpose (public or private)
This category includes publicly or privately owned land dedicated to governmental, institutional, infrastructure, utility, transportation, educational, recreational, or other public-serving functions that limit or preclude development. Note that public ownership alone does not automatically indicate that land should be excluded from the developable land inventory. The land must be actively committed to, or reserved for, a public use or purpose.
Examples of land committed to public use or purpose include:
- Active public schools and school campuses
- Municipal buildings and facilities (police, fire, emergency services, libraries, community centers, public works, transfer stations)
- Utility infrastructure and utility-owned land (water treatment plants, reservoirs, etc.)
- Transportation infrastructure (highways, airports, park-and-ride facilities)
- Cemeteries
- Active public parks and recreation complexes
- Institutional campuses serving a public purpose (hospitals, universities)
- Military or state-owned facilities
- Privately owned land permanently dedicated to a public function through easement, agreement, or operational use (e.g., a privately owned water supply reservoir subject to a public easement)
Data Resources
There is no single statewide comprehensive dataset of publicly committed land in Connecticut. The sources below, used in combination, provide a starting point to capture qualifying land area. Where more detailed or up-to-date local data is available, it should be prioritized over the statewide sources provided here, as local data will generally offer greater accuracy and specificity for a given municipality. Some overlap across sources is expected, but each may also identify areas the others miss. See the “Technical Guidance” section below for more details about using, filtering, spatializing, and querying these datasets.
Technical Guidance
Local data
Utility data, local zoning or public facilities layers, local institutional datasets, regional hazard mitigation plans, and other locally maintained data may be available at the local level. Where available, this local data should take precedence over the statewide sources listed below, as it is likely to be more current, more granular, and better tailored to local context. The statewide datasets are intended to fill gaps where local data is unavailable or incomplete, not to supersede it.
Parcel and CAMA Data
The CT GIS Office aggregates municipal parcel data annually. While locally published datasets may also be available, the statewide aggregation is publicly accessible through the CT Geodata Portal and the CT Housing Data Hub. Although this analysis is not conducted at the parcel level, parcel and CAMA data include useful attributes (such as ownership type, land use codes, and property classifications) that can help identify areas likely to qualify. This data is not edited or transformed by the CT GIS Office; questions about data quality or completeness should be directed to the local town assessor. For more information on CT parcel data aggregation, see the CT Geodata Portal page on parcels.
Parcel geometry: Connecticut CAMA and Parcel Layer (CT Housing Data Hub)
CAMA data: 2025 Connecticut Parcel and CAMA Data (CT Open Data Portal)
A. Owner Name Queries
Search the ownership attributes, “Owner” and “Co_Owner”, for terms including:
- “City of”
- “Town of”
- “State of”
- “United States of America”
- “School District”
- “Public Works”
- “Water Authority”
Example query logic:
OWNER_NAME LIKE '%CITY OF%'
OR OWNER_NAME LIKE '%TOWN OF%'
OR OWNER_NAME LIKE '%STATE OF%'B. State Use and State Use Description Queries
Search state use (“State_Use”) or use state use description (“State_Use_Description”) fields for terms related publicly oriented institutional and civic uses, including:
- Postal Service
- State
- Federal
- Education
- Library
- Hospital
- Cemetery
- Fire
- Police
- Recreation
- Municipal
- Government
- Utility
Example query logic:
STATE_USE_DESCRIPTION LIKE '%STATE%'
OR STATE_USE_DESCRIPTION LIKE '%FED%'
OR STATE_USE_DESCRIPTION LIKE '%EDUC%'
OR STATE_USE_DESCRIPTION LIKE '%LIBR%'C. Rights-of-Way
Public and private rights-of-way (ROW) should generally be excluded from a developable land inventory, as these areas are reserved for transportation, access, or utility purposes and are not typically available for development.
No comprehensive statewide GIS dataset currently exists publicly that consistently identifies all rights-of-way across Connecticut. However, the statewide parcel dataset contains parcel records that can often be used to identify ROW areas through parcel attribute information.
Identifying Rights-of-Way in the Parcel Dataset
Rights-of-way may be identified using keyword searches within the State Use Description field of the parcel dataset. Common keywords may include:
- “ROW”
Example query logic:
STATE_USE_DESCRIPTION LIKE '%ROW%'Because parcel data is compiled from municipal assessor records, terminology and attribute completeness vary considerably across jurisdictions. As a result, some municipalities may not consistently identify rights-of-way using standardized naming conventions or parcel attributes.
Where ROW polygons are present but not clearly identified through attribute queries, additional review methods may be used, where appropriate, including:
- Visual inspection of parcel geometry and spatial patterns
- Comparison with roadway centerline or transportation datasets
- Review of aerial imagery or basemap data
- Identification of narrow linear parcels associated with transportation or utility corridors
In municipalities where dedicated ROW polygons are not included in the parcel dataset, approximate rights-of-way areas may be derived by comparing the municipal boundary polygon to the aggregate parcel coverage. In these cases, the unassigned or residual land area between mapped parcel polygons and the municipal boundary may represent public rights-of-way or other unmapped areas.
CT Education Directory
There is no publicly available statewide GIS dataset representing public school locations in Connecticut. However, the Connecticut State Department of Education (CSDE) maintains a tabular dataset containing the official listing of public educational organizations, including district name, school name, street address, municipality, and ZIP code information.
Dataset: Education Directory (CT Open Data Portal)
The Education Directory provides location data as addresses. The Open Data Portal includes a column that contains latitude and longitude, since it was geocoded by an internal tool; this field can be used, but results should be verified thoroughly. If not using that field, users should geocode the records themselves to generate point features representing individual school locations. Once geocoded, the resulting points can be used to identify associated parcel polygons via a spatial selection or spatial join, selecting parcels that contain or intersect each point location.
Following the spatial selection process, identified parcels should be reviewed and verified using available parcel ownership and land use attributes. In many cases, qualifying school parcels can be confirmed based on ownership records indicating municipal, district, or other public ownership, and/or parcel use classifications identifying the property as a school, educational facility, or similar institutional use. Additional manual review may be necessary in situations where multiple parcels are associated with a single school campus or where ownership and land use information are ambiguous.
Geocoding references:
- Yale Center for Geospatial Solutions Lessons: Geocoding
- Geocoding: Longitude and Latitude by Address
After geocoding addresses to points, use this process to identify and extract polygons (parcels) based on their co-location with associated point features:
- Ensure matching coordinate systems
- Perform a spatial selection (often referred to as Select by Location)
- ArcGIS Pro: Select by Location, Spatial Join, Summarize Within
- QGIS: Extract by Location or Select by Location within Vector Selection, Join Attributes by Location
- Export or save the selected polygons
OpenStreetMap
OpenStreetMap (OSM) data may be used to identify features and land uses such as cemeteries, schools, libraries, parks, and other civic, recreational, or institutional facilities. OSM is a crowd-sourced geographic database maintained by volunteer contributors, and data completeness, positional accuracy, and attribute consistency can vary across locations. As a result, OSM should be used as a supplemental reference source to assist in feature identification and screening rather than as a primary authoritative dataset. Features identified through OSM should be reviewed and verified using authoritative GIS data, parcel information, aerial imagery, or other reliable sources where available.
Link: OpenStreetMap
3.2 Open space, parks, and recreation areas dedicated to the public or protected by a conservation easement
This category includes lands preserved for conservation, passive or active recreation, natural resource protection, or public enjoyment, where development is limited or prohibited by dedication or conservation restriction.
Examples include:
- Conservation areas and land trust properties
- Municipal, state, or federal parks
- Greenways and recreational trails
- Wildlife management areas
- Land subject to conservation easements
- Public beaches, boat launches, or recreational waterfront areas
- Agricultural preservation land protected through conservation programs
Data Resources
There is no single comprehensive dataset of open space, parks, and recreation areas in Connecticut. The following sources, used in combination, should capture most qualifying parcels and land area. Some overlap across sources is expected, but each may also identify areas the others miss. See the “Technical Guidance” section below for more details about using, filtering, spatializing, and querying these datasets.
- Local data
- Land trust inventories
- Parcel and CAMA data
- CT DEEP Property
- CT DEEP Protected Open Space (2011)
- CT DEEP Federal Open Space
- CT DEEP 1997 Municipal and Private Open Space Property
- Connecticut Greenways
- USGS PAD-US
Technical Guidance
Local data
Open space inventories, parks and recreation department data, land trust records, POCD (Plan of Conservation and Development) land use and open space maps, and other municipally or regionally maintained datasets may be available locally. Where available, this data should take precedence over the statewide sources listed below, as it is likely to be more current, more granular, and better tailored to local context. The statewide datasets are intended to fill gaps where local data is unavailable or incomplete, not to supersede it.
Land trust inventories
Land trusts may own land outright, hold a conservation easement on land owned by another party, or both. Not all land owned by a land trust is permanently protected. Ownership alone does not guarantee a conservation easement or other permanent restriction is in place. Land trust holdings should only be included in this inventory where the land is confirmed to be protected by a conservation easement or other permanent legal restriction. Land trust-owned land that is not protected by such a restriction should not be included.
No comprehensive statewide GIS dataset exists for land trust holdings in Connecticut. The Connecticut Land Conservation Council (CLCC) maintains a statewide directory of Connecticut land trusts that can be used to identify organizations operating within a municipality or region.
Source: CLCC Land Trust Inventory (CLCC)
The Connecticut Open Space Parcels (CT Housing Data Hub) layer includes land trusts as identified through ownership from the parcel and CAMA dataset. See the Parcel and CAMA Data section below for more details.
Parcel and CAMA Data
The CT GIS Office aggregates municipal parcel data annually. While locally published datasets may also be available, the statewide aggregation is publicly accessible through the CT Geodata Portal and the CT Housing Data Hub. Although this analysis is not conducted at the parcel level, parcel and CAMA data include useful attributes (such as ownership type, land use codes, and property classifications) that can help identify areas likely to qualify. This data is not edited or transformed by the CT GIS Office; questions about data quality or completeness should be directed to the local town assessor. For more information on CT parcel data aggregation, see the CT Geodata Portal page on parcels.
Parcel geometry: Connecticut CAMA and Parcel Layer (CT Housing Data Hub)
CAMA data: 2025 Connecticut Parcel and CAMA Data (CT Open Data Portal)
A. Owner and Co-Owner Queries
Search the owner (“Owner”) and co-owner (“Co_Owner”) fields for terms that contain conservation related ownerships, including:
- Land trust
- Conservation or conservancy
- Land alliance
Example query logic:
OWNER LIKE '%LAND TRUST%'
OR OWNER '%CONSERVATION%'
OR OWNER '%LAND ALLIANCE%'B. State Use and State Use Description Queries
Search state use and state use description for open space and recreation terms, including:
- Open (for Open Space)
- Forest
- Recreational
Example query logic:
STATE_USE_DESCRIPTION LIKE '%OPEN%'
OR STATE_USE_DESCRIPTION LIKE '%FOREST%'
OR STATE_USE_DESCRIPTION LIKE ''%REC%'CT DEEP Property
CT DEEP publishes a polygon feature layer representing property that comprises DEEP facilities such as state forests, parks, and wildlife management areas.
Dataset: DEEP Property (CT Housing Data Hub)
DEEP Property is a polygon feature-based layer that includes all land owned in fee simple interest by the State of Connecticut Department of Energy and Environmental Protection. This layer is based on information that was collected and mapped at various scales and at different levels of accuracy. Generally, partial interests such as easements or development rights are not included in this layer. The exception is flood control areas, which may include permanent easements. Types of property in this layer include parks, forests, wildlife areas, flood control areas, scenic preserves, natural areas, historic reserves, DEEP owned waterbodies, water access sites and other miscellaneous properties. This layer is current and is updated as parcels are acquired by DEEP.
This dataset is regularly maintained by CT DEEP and should be used to ensure that all properties identified through the parcel query in the Parcel and CAMA Data section above are fully accounted for.
CT DEEP Protected Open Space (2011)
This was created as part of the CT DEEP Protected Open Space Mapping (POSM) Project in 2011. Not all CT towns are included in this inventory. See more detailed information about the contents of the dataset in the data description on the data page.
Dataset: 2011 Protected Open Space Mapping Set (CT Housing Data Hub)
This dataset has not been updated since 2011, so it should be used as reference only.
CT DEEP Federal Open Space
This dataset of Federal Open Space, published by CT DEEP, contains parcels of open space land owned by various agencies of the Federal government. It includes parcels owned in fee simple interest and partial interest, such as easements. Types of Federal open space include recreation areas created by the U. S. Army Corps of Engineers in the construction of flood control dams, such as Mansfield Hollow, Thomaston Dam, Colebrook River Lake and Hop Brook Lake; portions of the Appalachian Trail in northwest Connecticut owned by the National Park Service; and scenic and preservation easements, such as the scenic easements located along the Housatonic River in Kent, Cornwall and Canaan, and along the Connecticut River.
Dataset: Federal Open Space (CT Housing Data Hub)
This layer has not been updated since 2004 and may not be accurate, so it should be used as reference only. For more information on this dataset, see the CT ECO Federal Open Space Guide.
CT DEEP 1997 Municipal and Private Open Space Property
1997 Municipal and Private Open Space Property, published by CT DEEP, is polygon feature-based data that includes land owned in fee simple interest by the municipalities, land trusts, and other private entities within the State of Connecticut.
Dataset: 1997 Municipal and Private Open Space (CT Housing Data Hub)
Municipal and Private Open Space Property contains parcels owned by municipalities, land trusts and other private entities throughout the state. Generally, these parcels are open space and include schools, cemeteries, recreation, conservation and preservation land. This layer can be used with the Federal Property and DEP Property layers for a more comprehensive understanding of open space and recreation land throughout the State of Connecticut.
This layer has not been updated since 1997 and may not be accurate. For more accurate and current open space parcel data, please see the Protected Open Space and the Protected Open Space Phase 1 feature classes. This should be used as reference only.
Connecticut Greenways
Dataset: Official Designated Connecticut Greenways (CT Housing Data Hub)
The CT Greenways Council and Department of Energy & Environmental Protection have designated these greenways of State significance based upon established criteria. CT Public Act 95-335 defines a greenway as a “corridor of open space” that:
- may protect natural resources, preserve scenic landscapes and historical resources or offer opportunities for recreation or non-motorized transportation;
- may connect existing protected areas and provide access to the outdoors;
- may be located along a defining natural feature, such as a waterway, along a man-made corridor, including an unused right of way, traditional trail routes or historic barge canals; or
- may be a green space along a highway or around a village.
While this dataset represents Connecticut Greenways as polyline features rather than polygons delineating the full extent of the designated corridors, it provides a useful reference for identifying their general geographic locations and alignments. The line features are intended to represent the approximate routes of the designated greenways and should not be interpreted as the full area or boundaries of the protected corridors.
USGS Protected Areas Database of the United States
The USGS Protected Areas Database of the United States (PAD-US) is a national geospatial dataset that inventories protected public lands and conservation areas across the United States. The dataset includes federal, state, local, and nonprofit conservation lands, as well as lands managed for recreation, natural resource protection, open space, and other protected uses.
Dataset: PAD-US Protection Mechanism Category (CT Housing Data Hub)
PAD-US can serve as an important reference dataset for identifying existing protected and open space lands that may be excluded under this methodology. Because the dataset compiles information from many agencies and organizations, it should be used in conjunction with parcel data, local open space inventories, and other authoritative state or municipal sources.
The PAD-US program maintains published documentation and methodology describing data sources, compilation methods, protection classifications, and update processes. Users should review the official documentation to understand dataset limitations and interpretation considerations.
Use this layer as a supplemental reference source for open space and protected lands analysis.
3.3 Land subject to enforceable restrictions or prohibitions on development
This category includes land where development is legally restricted by deed, agreement, or other enforceable instruments. Some properties in this category may be covered in other exclusion categories, such as public use or open space.
Examples include:
- Deed-restricted properties
- Easements
- Land Trust agreements
Guidance on deed-restricted properties
To the extent that municipality-wide restriction data is digitally available, it should be incorporated into the developable lands inventory at this stage. Municipalities are not required by statute to undertake deed research to obtain this information. Detailed parcel-level research on specific deed restrictions may hold greater importance in other elements of the housing growth planning process when specific areas are evaluated.
3.4 Wetlands or watercourses, as defined in the Wetlands and Watercourses Act (C.G.S. Chapter 440)
Wetlands and watercourses are defined under the CT Wetlands and Watercourses Act (C.G.S. Chapter 440) and include inland wetlands, watercourses, and related regulated areas subject to environmental protection and development limitations.
Connecticut wetlands and watercourses are defined as follows:
CT Inland Wetlands and Watercourse Act define inland wetlands by soil type. The soil types are poorly drained, very poorly drained, alluvial, and floodplain.
The Act also defines the term watercourses very broadly to mean rivers, streams, brooks, waterways, lakes, ponds, marshes, swamps, bogs and all other bodies of water, natural or artificial, vernal or intermittent, public or private. Although the Act defines inland wetlands and watercourses separately, they occasionally may represent the same area as in the case of a marsh or swamp.
Unlike inland wetlands which are defined by soil type and typically regulated by the municipalities of CT, tidal wetlands are defined in the Tidal Wetlands Act by their current or former tidal connection, and their capacity to support certain wetland vegetation. Tidal wetlands are regulated exclusively by the CT DEEP and not by municipal inland wetlands agencies.
CT DEEP, How are Inland Wetlands and Watercourses Defined in Connecticut?
Data Resources
- Soils Inland Wetland
- High Resolution Tidal Marsh Datasets
- Connecticut Hydrography Set
- Local data
- National Wetlands Inventory
Technical Guidance
Local data
Datasets may be available from your municipality’s inland wetlands agency. If available, local mapping can provide greater detail and more current information than statewide datasets.
Soils Inland Wetland
This dataset from CT DEEP is derived from Connecticut Soil Survey Geographic Database (SSURGO) data and identifies wetland and non‑wetland soils as defined by the Connecticut Inland Wetlands and Watercourses Act.
Dataset: Soils Inland Wetland (CT Housing Data Hub)
The SSURGO contains soil information compiled by the National Cooperative Soil Survey over the course of nearly a century, and the State of Connecticut defines inland wetlands based on soil characteristics. Under the Connecticut Inland Wetlands and Watercourses Act, wetland soils include any soil types designated as poorly drained, very poorly drained, alluvial, or floodplain by the National Cooperative Soil Survey, as periodically amended by the Natural Resources Conservation Service of the U.S. Department of Agriculture.
To delineate soil-defined inland wetlands, the CT DEEP Inland Wetland Soils feature layer should be queried using the “CTInlWet” attribute field, selecting records where the value equals “CT wetland.” The selected polygons represent soils meeting Connecticut’s regulatory wetland criteria and provide a statewide representation of inland wetland areas for mapping and analysis purposes. The resulting dataset may be included in the final map described in Section 5.
High Resolution Tidal Marsh Datasets
Detailed tidal wetland mapping is available through CT DEEP and was developed using high-resolution lidar and aerial imagery survey of all the protected coastal marshland across the state of Connecticut. The data are available through the CT ECO geoSAP viewer and may be downloaded for GIS analysis.
Dataset: High Resolution Marsh Mapping (CT ECO)
Connecticut Hydrography Set
The CT National Hydrography Dataset (NHD) is published by CT DEEP as the Connecticut Hydrography Set, including both polygon and line features.
Dataset: Connecticut Hydrography Set (CT Housing Data Hub)
At this time, the NHD remains the best available statewide geospatial dataset for identifying surface water features across Connecticut. As of October 1, 2023, the NHD was retired. NHD data will continue to be available but no longer maintained or updated. The most current hydrography data for Connecticut will eventually be provided through the USGS 3D Hydrography Program (3DHP), which is currently in development and will offer a higher‑resolution surface water dataset. Once the 3DHP for Connecticut is completed and released, it will replace the NHD as the recommended dataset in this guidance (estimated 2027/2028).
As part of the Connecticut Hydrography Set, the Hydrography Poly layer includes polygon features that represent areas of water for rivers, streams, brooks, reservoirs, lakes, ponds, bays, coves, and harbors. Polygon features also depict inundation areas, marshes, dams, aqueducts, canals, tidal flats, shoals, rocks, channels, and island. For this analysis, the polygon features will give the best surface area cover estimation of surface water in CT.
National Wetlands Inventory
The National Wetlands Inventory (NWI), maintained by the U.S. Fish & Wildlife Service, provides a comprehensive, nationwide dataset of wetland locations and types. While Connecticut defines wetlands by statute based on hydric soils, which may differ from the federal classification approach, the NWI can still serve as a useful supplemental reference when analyzing wetland coverage.
Dataset: USA Wetlands (CT Housing Data Hub)
3.5 Areas of 0.5 acres or more of contiguous land that are unsuitable for development due to topography (such as steep slopes)
Areas with unsuitable topography may not be reasonably available for development due to physical site constraints. While steep slopes are explicitly mentioned in the statutes and should be excluded from the developable land inventory, other considerations may include areas with significant soil erosion hazards and areas with shallow bedrock. While some of these areas may be technically developable, towns may consider excluding them from the developable land inventory for the purposes of this planning analysis.
Data Resources
Technical Guidance
Local Data
Local slope analyses, soil surveys, geotechnical studies, and other municipally or regionally maintained topographic data may be available locally. Where available, this data can take precedence over the statewide sources listed below, as it may be more current, more granular, and better tailored to local site conditions. The statewide datasets are intended to fill gaps where local data is unavailable or incomplete, not to supersede it.
Connecticut Steep Slope Areas
This dataset was derived from the 2023 Digital Elevation Model (DEM) generated from the 2023 spring imagery and lidar capture. The steep slopes layer was developed from 10-foot and 2-foot per pixel DEM data and identifies areas classified as Moderate (10%–15%), Steep (15%–20%), and Very Steep (20%+) slopes. The feature layer is provided as polygons and includes fields identifying the municipality and COG. Detailed methodology for the development of this dataset is available on the data page.
Dataset: Connecticut Steep Slope Areas (CT Housing Data Hub)
We recommend using the 2-foot contour layer, as it provides the highest level of detail available. To use this layer, query the dataset for the area of interest (municipality or COG) and select the slope category or categories appropriate for the analysis. If alternative slope thresholds are desired, the DEM data and published methodology may be used to develop additional slope classifications.
The statute specifies “areas of 0.5 acres or more of contiguous land.” Because contiguity is not explicitly defined and may be interpreted differently, this guidance does not prescribe a single methodology for identifying such areas. One reasonable approach is to use the steep slope polygons and filter for polygons greater than 0.5 acre in size. Since adjacent raster cells meeting the slope threshold are grouped into a single polygon during processing, the resulting polygons may serve as a useful proxy for contiguous areas. Municipalities may also use lidar-derived elevation data, contours, hillshade, or other terrain analyses to validate or refine the results based on local conditions.
All Soils Dataset
This dataset is a SSURGO-based soil dataset published by CT DEEP for Connecticut. It represents a digital soil survey and provides detailed soil geographic information developed through the National Cooperative Soil Survey program. It is generally the most detailed level of soil data available for statewide analysis. Additional information and metadata are available on the data page.
Dataset: Soils All Soils (CT Housing Data Hub)
To use this layer, refer to the soil attributes relevant to erosion hazard or related soil characteristics and query the dataset for the area of interest.
Bedrock Geology Set
This dataset is a polygon and line feature-based layer describing the solid material that underlies soil or other unconsolidated material across Connecticut. It represents mapped bedrock geology and is intended for use in understanding underlying geologic conditions at a statewide scale. Additional information is available on the data page.
Dataset: Bedrock Geology Set (CT Housing Data Hub)
To use this layer, query the dataset for the area of interest and review the mapped bedrock units in relation to shallow bedrock or other considerations.
See more information from CT DEEP about Statewide Geologic Maps.