Salt Water Limit is a 1:24000-scale, line feature-based layer that depicts the approximate salt water limits of watercourses and embayments in coastal Connecticut. It is important to note that the exact demarcation of the salt-water extent is often not accurate. As stated in the report known as Source 1 in this metadata ("The Boundary Between Freshwater and Saltwater in Connecticut"): "Any definition and demarcation of the boundary between saltwater and freshwater is, of necessity, an approximation. The boundary is transitory and, at times, vague. Within a given body of water, it may vary from day to day, season to season, and year to year, according to such predictable and unpredictable factors as tidal magnitude, rate of evaporation, climatological and meteorological factors, estuarine circulation patterns, and the degree of vertical salinity stratification. An exact delimitation of the upstream limits of saltwater would be a difficult task and one that is probably not necessary for the purposes of coastal management in Connecticut. However, since the primary goal of Connecticut's Coastal Area Management Program is to provide for the balanced, coordinated management of coastal resources, the coastal waters of the state must be clearly and uniformly defined as required in federal and state legislation."
The source data for this layer (a compilation of reports and maps) varied in cartographic scale and age but features were digitized onto standard 1:24,000 scale US Geological Survey (USGS) topographic quadrangle maps. Because of this, the layer does not represent conditions at any particular point in time, nor does every waterbody have an associated salt water extent. This data layer has been updated in 2005 to include more robust attribute information, but no further updates are planned.
Attribute information is comprised of an AV_LEGEND attribute that identifies the feature as the salt water extent ("Salt Limit"), eight "DATASRC[1-8]" attributes that contain a boolean (0,1) value identifying whether or not that particular source was used, a NOTES attribute for additional data source descriptions, a QUADNUMBER attribute and a QUAD_NAME attribute.For additional information, refer to the various source data provided in the Source section of this metadata.
publication date
Salt Water Limit represented as line features. (Source: State of Connecticut, Department of Environmental Protection)
Internal feature number. (Source: ESRI)
Feature geometry. (Source: ESRI)
Data source used: USGS field data topographic maps. (Source: State of Connecticut, Department of Environmental Protection)
| Value | Definition |
|---|---|
| 0 | Data source not used. |
| 1 | Data source used. |
Data source used: "Water Resources Inventories" and "Hydrogeologic Data" (Parts 3,4,5,8,10) (Source: State of Connecticut, Department of Environmental Protection)
| Value | Definition |
|---|---|
| 0 | Data source not used. |
| 1 | Data source used. |
Data source used: Map entitled "Dissolved Solids in Streams and Groundwater on North Coast of Lond Island Sound, Connecticut" (Source: State of Connecticut, Department of Environmental Protection)
| Value | Definition |
|---|---|
| 0 | Data source not used. |
| 1 | Data source used. |
Data source used: Unpublished map, "Extent of Saltwater Influence" (USGS) (Source: State of Connecticut, Department of Environmental Protection)
| Value | Definition |
|---|---|
| 0 | Data source not used. |
| 1 | Data source used. |
Data source used: "Tidal Wetlands of Connecticut: Vegetation and Associated Animal Populations" (Source: State of Connecticut, Department of Environmental Protection)
| Value | Definition |
|---|---|
| 0 | Data source not used. |
| 1 | Data source used. |
Data source used: Map overlays showing state-regulated tidal wetlands (Source: State of Connecticut, Department of Environmental Protection)
| Value | Definition |
|---|---|
| 0 | Data source not used. |
| 1 | Data source used. |
Data source used: Other studies (sources noted on maps) (Source: State of Connecticut, Department of Environmental Protection)
| Value | Definition |
|---|---|
| 0 | Data source not used. |
| 1 | Data source used. |
Data source used: Estimation based on topography, obvious constructions, and salinity of nearby bodies of water (Source: State of Connecticut, Department of Environmental Protection)
| Value | Definition |
|---|---|
| 0 | Data source not used. |
| 1 | Data source used. |
Text describing data source if other than Data Sources 1 through 8. (Source: State of Connecticut, Department of Environmental Protection)
Name of USGS quadrangle in string format. (Source: State of Connecticut, Department of Environmental Protection)
| Value | Definition |
|---|---|
| Ansonia | Quad Name |
| Branford | Quad Name |
| Bridgeport | Quad Name |
| Clinton | Quad Name |
| Deep River | Quad Name |
| Essex | Quad Name |
| Glennville | Quad Name |
| Guilford | Quad Name |
| Hamburg | Quad Name |
| Milford | Quad Name |
| Mystic | Quad Name |
| New Haven | Quad Name |
| New London | Quad Name |
| Niantic | Quad Name |
| Norwalk South | Quad Name |
| Norwich | Quad Name |
| Old Lyme | Quad Name |
| Old Mystic | Quad Name |
| Sherwood Point | Quad Name |
| Stamford | Quad Name |
| Uncasville | Quad Name |
| Watch Hill | Quad Name |
| Westport | Quad Name |
| Woodmont | Quad Name |
Feature geometry. (Source: ESRI)
Number of USGS quadrangle in string format. (Source: State of Connecticut, Department of Environmental Protection)
| Value | Definition |
|---|---|
| 72 | Quad Number 72 |
| 84 | Quad Number 84 |
| 85 | Quad Number 85 |
| 87 | Quad Number 87 |
| 88 | Quad Number 88 |
| 94 | Quad Number 94 |
| 95 | Quad Number 95 |
| 96 | Quad Number 96 |
| 97 | Quad Number 97 |
| 98 | Quad Number 98 |
| 99 | Quad Number 99 |
| 100 | Quad Number 100 |
| 101 | Quad Number 101 |
| 102 | Quad Number 102 |
| 103 | Quad Number 103 |
| 104 | Quad Number 104 |
| 108 | Quad Number 108 |
| 109 | Quad Number 109 |
| 110 | Quad Number 110 |
| 111 | Quad Number 111 |
| 112 | Quad Number 112 |
| 113 | Quad Number 113 |
| 114 | Quad Number 114 |
| 115 | Quad Number 115 |
Includes the source data used to define each feature (DATASRC[1-8]), comments regarding the feature if alternate data sources are used (NOTES), number of the USGS quadrangle (QUADNUMBER), and name of the quadrangle (QUAD_NAME) feature is located on
79 Elm Street
Salt Water Limit is 1:24,000 scale data. Use this layer along with layers such as Hydrography Arcs and Polygons and Town boundaries to show the limits of salt water extent in Connecticut. Due to the source data and its compilation methods, use of this layer at scales larger than 1:24000 is not recommended.
This report was prepared by the Connecticut Department of Environmental Protection and explains in detail the methods, scientific or reference based, used to determine salt water extent. Included in this report are descriptions of the maps and other data that formed the bases for the final determination of salt water extent. These maps and data are further described as Sources 2 through 10 in this metadata.
Primary source referenced and explained in detail in the Source 1 report, as follows: "These maps, available for only a portion of the coastal area, are the original maps used by the USGS to record field data for mapping dissolved solids concentrations and other water quality parameters in surface water. They show specific conductance measurements for various sites under conditions of high tide and low streamflow (80% or greater duration). For use in this study, the specific conductance measurements have been converted to dissolved solids using 0.68 as a multiplier. While the conversion factor (multiplier) varies between drainage basins and within each basin, 0.68 represents an average conversion figure and is adequate for use in the areas for which the above data are available."
Additional source referenced and explained in detail in the Source 1 report, as follows: "[This map] is based on data compiled by the USGS for its inventories of Connecticut’s drainage basins ...and uses symbols to denote dissolved solids concentrations in streams at low flow. The following categories are used (in milligrams per liter or parts per million): 0-100, 100-300, 361-500, more than 500.
Additional source referenced and explained in detail in the Source 1 report, as follows: "This unpublished map uses hand-drawn lines to demarcate the boundary between saltwater and freshwater. The extent of saltwater influence on this map corresponds closely to a concentration of 0.5ppt dissolved solids. USGS officials indicate that this map is essentially an unrefined version of Dissolved Solids in Streams and Groundwater. However, this map has been included as a source of information because it is more legible than Dissolved Solids in Streams and Groundwater."
Additional source referenced and explained in detail in the Source 1 report, as follows: "The content of these reports varies from basin to basin with some giving almost exclusive attention to groundwater, and others giving a little more information on surface water. Most reports present streamflow data, records of selected wells, and water quality data for both groundwater and surface water. The latter includes concentrations of iron, chloride, dissolved solids and turbidity among others. These reports were of limited use to this study because the monitoring sites, especially for surface water, are fairly spread out and few are located in the vicinity of the freshwater-saltwater boundary."
Additional source referenced and explained in detail in the Source 1 report, as follows: "Of the five coastal drainage basins, published inventories exist for the Lower Thames and Southeastern Coastal River Basins (Part 3), Southwestern Coastal River Basin (Part 4), and Lower Housatonic River Basin (Part 5). The inventories for the Quinnipiac River Basin (Part 8) and the Lower Connecticut River Basin (Part 10) are being prepared. The Water Resources Inventories function as interpretative reports for the data presented in Hydrogeologic Data. They contain summaries of streamflow characteristics and water quality in addition to providing tables, graphs, and maps summarizing various types of data. The maps depicting dissolved solids concentrations along with the extent of saltwater influence were particularly useful to this study."
Additional source referenced and explained in detail in the Source 1 report, as follows: "This study, conducted by Drs. Niering and Warren, their colleagues, and students at Connecticut College in New London, analyzed the vegetation of 127 marsh areas, representing 12,174 acres of the state’s 15,586 acres. Most marshes exhibit a bay to upland sequence of vegetation belts recognized by Miller and Egler (1950) including Spartina alterniflora lower slope (intertidal zone), Spartina patens upper slope (high marsh), Juncus gerardi (lower border), and Panicum virgatum (upper border). Within this pattern, a mosaic of various subtypes is usually apparent. Niering’s study describes the abundance of various species of flora and fauna in addition to major environmental impacts (dredging, ditching, tidal gates, construction, etc.) for each marsh area surveyed. Although the study areas are not mapped, many are described in sufficient detail so that their boundaries may easily be determined using USGS 1:24,000 scale topographic maps in conjunction with maps depicting state-regulated tidal wetlands. All of the areas surveyed are dominated by salt-dependent vegetation. In a few cases these wetlands extend into areas of freshwater influence and this is noted by the authors. Although no salinity measurements were taken, the existence of certain types of vegetation can be used as an indication that the salt content of the surrounding water exceeds 0.5ppt. The information provided in Niering’s study has been used both as a secondary source to verify USGS data and as a primary source for areas where no other data were available. The salt marsh descriptions were especially valuable in determining the extent of saltwater influence in small streams and creeks."
Additional source referenced and explained in detail in the Source 1 report, as follows: "These overlays, showing the boundaries of state-regulated tidal wetlands, were used as a secondary source to locate the areas described by Niering’s study (See III c), to resolve conflicts between other data sources, and in a few cases to approximate the extent of saltwater influence where no other data were available."
Additional sources noted on the published salt water extent paper maps were used.
This source consists of topography, obvious constrictions and salinitiy of nearby bodies of water. An explanation is provided below (taken from Source 1 report, p. 12): "Topography: For the watercourses for which there are adequate data, the extent of saltwater influence rarely extends farther upstream than the 10-foot contour as it appears on USGS topographic maps. Obvious constrictions: These constrictions tend to reduce or block the upstream flow of saltwater resulting from the incoming tide. They may also influence the downstream flow of freshwater but their greatest effect is generally on saltwater circulation.. Man-made constrictions include tidal gates, dams, bridge foundations and causeways. Natural constrictions include land patterns of the adjacent shorelands and the addition of freshwater from tributaries. Examination of Surrounding Bodies of Water: If larger bodies of water located near the stream in question are saline and no major sources of freshwater are located directly upstream from the area under examination, the stream is considered to be saline up to a reasonable point determined by topography and the existence of constrictions. The method of estimation described above ... was used only for a few small streams and creeks where its use was dictated by a lack of any other applicable data."
Salt water extent areas were drawn onto these maps based on data provided in the preceding sources.
This data source refers to all features combined in one statewide layer. Note that although this is a statewide layer, not every waterbody will have an associated salt water extent. Since initial publication in 1995, subsequent publications or editions of the layer were generated by the State of Connecticut in order to convert from NAD 27 to NAD 83 geographic coordinate system. Consequently, different copies of this layer were produced, representing various steps in the data layer development and maintenance process (metadata lineage). Changes made to the entire layer are reflected in metadata process steps where this particular data source is cited as both the Source Used and the Source Produced.
Creation of Topographic Maps Showing Salt Water Limits - Data from the two small scale maps ("Extent of Saltwater Influence" [Source 4] and "Dissolved Solids in Streams and Groundwater [Source 3]") and the maps containing the original USGS field data [Source 2] were plotted on blueline copies of coastal area topographic maps (1:24,000). Areas lacking adequate data and areas showing conflicts between data sources were noted. Subsequently, each map quadrangle was examined using the remaining sources of data in addition to those already plotted in order to mark the boundary as close as possible to the actual extent of saltwater influence as defined in the Source 1 report.79 Elm Street
Feature digitizing and attribution (digitizing tablet method) - Using ESRI ArcInfo software, features were digitized by registering the source map (Source 11) to the digitizing tablet and using the crosshairs of the digitizer's mouse to manually capture the geometry (location) of features drafted on the map. The corners of the USGS 7.5 minute topographic quadrangle maps are used as registration points and are depicted on the source map. The source map was registered to the digitizing tablet by digitizing (entering) the locations of four quadrangle corner registration points shown on the map. Individual features were manually digitized off the source map and assigned a "0" or "1" value in the appropriate DATASRC attribute field to denote the source used for that particular feature. Because there were eight original sources as described in the "Boundary Between Saltwater and Freshwater in Connecticut" (Source 1 in this metadata), eight DATASRC attribute fields were created and named DATASRC1 through DATASRC8. Some features used more than one source, whiles others did not use any of the eight sources and instead were coded as zero's ("0") in each DATASRC attribute field. In those cases, an explanation of the alternate source used for that feature was entered as text into the NOTES attribute field. The quadrangle number and the quadrangle name for each feature were also entered into the QUADNUMBER and QUAD_NAME attribute fields, respectively. Feature location and attribute accuracy was visually checked and inspected by symbolizing and labeling features according to attribute value on the computer screen and on the hard copy toopgraphic maps.Datum conversion - Using DEPGIS Connecticut NADCON Extension for ESRI ArcView 3 software, this layer was converted from the Connecticut State Plane Coordinate System of 1927 (NAD27) to the Connecticut State Plane Coordinate System of 1983 (NAD83). The NADCON (North American Datum CONversion) data transformation was used.
The Salt Water Limit layer retains the feature types and information identified by the State of Connecticut, Department of Environmental Protection and obtained from various sources identified in the Source section of this metadata. All attributes have valid values. Values are within defined domains.
The horizontal positional accuracy of this data is unknown.
The completeness of the data reflects the feature content of the data sources. The Salt Water Limit layer is complete in the sense that it accurately reflects the contents of the source information available at the time the State of Connecticut, Department of Environmental Protection created the layer. This data is not updated.
Line features conform to the following topological rules. Lines are single part. There are no duplicate lines. Lines do not self overlap. Lines may overlap other lines. No automated procedures or tests were performed to guarantee desired topology other than visual inspection.
No restrictions or legal prerequisites for using the data. Because the scale of the source data is varied, use caution when displaying this data. Although this data set has been used by the State of Connecticut, Department of Environmental Protection, no warranty, expressed or implied, is made by the State of Connecticut, Department of Environmental Protection as to the accuracy of the data and or related materials. The act of distribution shall not constitute any such warranty, and no responsibility is assumed by the State of Connecticut, Department of Environmental Protection in the use of these data or related materials. The user assumes the entire risk related to the use of these data. Once the data is distributed to the user, modifications made to the data by the user should be noted in the metadata. When printing this data on a map or using it in a software application, analysis, or report, please acknowledge the State of Connecticut, Department of Environmental Protection as the source for this information.
79 Elm Street
| Data format: | in format Shapefile, Feature Class (version ArcGIS) |
|---|---|
| Network links: | http://www.ct.gov/deep |
The data distributor does not provide custom GIS analysis or mapping services. Data is available in a standard format and may be converted to other formats, projections, coordinate systems, or selected for specific geographic regions by the party receiving the data.
79 Elm Street