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Connecticut Local Drainage Basins Line

Frequently-asked questions:


What does this data set describe?

Title:
Connecticut Local Drainage Basins Line

Abstract:
Connecticut Local Drainage Basins is 1:24,000-scale, polygon and line feature data that define local drainage basin areas in Connecticut. These relatively small basin areas mostly range from 0.5 to 8 square miles in size and make up, in order of increasing size the larger subregional, regional, and major drainage basin areas. Connecticut Local Drainage Basins includes drainage areas for all Connecticut rivers, streams, brooks, lakes, reservoirs and ponds published on 1:24,000-scale 7.5 minute topographic quadrangle maps prepared by the USGS between 1969 and 1984. Data is compiled at 1:24,000 scale (1 inch = 2,000 feet). This information is not updated.

Polygon and line features represent drainage basin areas and boundaries, respectively. Each basin area (polygon) feature is outlined by one or more major, regional, subregional, and local basin boundary (line) feature. These data include 2,898 local basin area (polygon) features and 8,663 local basin boundary (line) features.

Local Basin area (polygon) attributes include major, regional, subregional, and local basin number, and feature size in acres and square miles. The local basin number (LBAS_NO) uniquely identifies individual basins and is 7 characters in length. There are 2,895 unique local basin numbers. Examples include 6000-00, 4300-00, and 6002-00. The first digit (column 1) designates the major basin, the first two digits (columns 1-2) designate the regional basin, the first 4 digits (columns 1-4) designate the subregional basin, and the first seven digits (columns 1-7) designate the local basin. Note, there are slightly more local basin polygon features (2,898) than unique local basin numbers (2,895) primarily due to a few stream confluences that split the same local basin into two polygon features.

Local basin boundary (line) attributes include a drainage divide type attribute (DIVIDE) used to cartographically represent the hierarchical drainage basin system. This divide type attribute is used to assign different line symbology to major, regional, subregional, and local drainage basin divides. For example, major basin drainage divides are more pronounced and shown with a wider line symbol than regional basin drainage divides.

Connecticut Local Drainage Basin polygon and line feature data are derived from the geometry and attributes of the Connecticut Drainage Basins data.

Supplemental information:
A standardized mapping of natural drainage basins in Connecticut was completed in 1981 by the Connecticut Department of Environmental Protection. This drainage basin system divided Connecticut into 8 major basins, 45 regional basins, 337 subregional basins, 2,898 local basins, and 7,067 small drainage basin areas. Major basins are subdivided into regional basins. Regional basins are subdivided into subregional basins. Subregional basins are subdivided into local basins. Local basins are subdivided into smaller drainage basin areas for impoundments and river reaches. 

A pair of 1:24,000-scale polygon and line feature classes is available for all basin levels. These data are named Connecticut Major Basins, Connecticut Regional Basins, Connecticut Subregional Basins, Connecticut Local Basins, and Connecticut Drainage Basins. Connecticut Drainage Basins includes the most detailed information upon which the other basin datasets are based.

A hierarchical drainage basin number was assigned to uniquely identify drainage basin areas. Drainage basin areas are numbered sequentially beginning upstream and proceeding downstream. The first digit (column 1) identifies the major basin, the first two digits (columns 1-2) identify the regional basin, the first 4 digits (columns 1-4) identify the subregional basin, and the first seven digits (columns 1-7) identify the local basin. Below are examples of the hierarchical drainage basin numbers.

Basin Numbers:

4 = Major drainage basin number, MBAS_NO (column 1)
43 = Regional drainage basin number, RBAS_NO (columns 1-2)
4302 = Subregional drainage basin number, SBAS_NO (columns 1-4)
4302-04 = Local drainage basin number, LBAS_NO (columns 1-7)
4302-04-1-R12 = Basin drainage identification number, BASIN_NO (columns 1-13)

Stream Order (column 9):

4304-00-1 = Stream order value of 1 represents a headwater basin.
4304-00-2 = Stream order value > 1 denotes the complexity of the drainage basin morphology.

Mapping Status Element (column 10):

4302-00-2- = Ending with minus sign (-) denotes detail mapping at 1:24,000 scale for entire basin.

4302-00-2+ = Ending with plus sign (+) denotes detailed mapping not performed at 1:24,000 scale for the entire drainage basin. The Stream Order value will not reflect the complexity of the drainage basin morphology.

4302-00-1* = Ending with asterisk sign (*) denotes a headwater basin containing a delineated impoundment into which a delineated drainage basin outlets.

Reach-Impoundment Identifier (column11) and Number (column 12-13):

4302-00-1-L1 = The value for the Reach-Impoundment Identifier for an impounment basin is L (for lake). It is followed by the Reach-Impoundment Number (1).

4302-04-1-R12 = The value for the Reach-Impoundment Identifier for a stream reach basin is R (for reach). It is followed the Reach-Impoundment Number (12).

  1. How should this data set be cited?

    State of Connecticut, Department of Environmental Protection (data compiler, editor and publisher), 1988, Connecticut Local Drainage Basins Line: State of Connecticut, Department of Environmental Protection, Hartford, Connecticut, USA.

    Online links:
    Other citation details:
    The State of Connecticut, Department of Environmental Protection is the collector of the data (compiler), the creator and maintainer of the data layer (editor), and producer (publisher) of this information for use. Data compiled and digitized from the 1:24,000-scale compilation sheets for the 1:125,000-scale Natural Drainage Basins in Connecticut Map, McElroy, 1981. The 2006 Edition includes the same basin features originally published in 1988 with some minor corrections and improvements made to feature attribute information. Previously undetected errors have been corrected and are included in this 2006 edition. This data is not updated. Source map scale is 1:24,000.

    This is part of the following larger work:

    Marianne McElroy, State of Connecticut, Department of Environmental Protection, Natural Resources Center, 1981, Natural Drainage Basins in Connecticut: Connecticut Natural Resources Atlas SeriesDrainage Basins Map, State of Connecticut, Department of Environmental Protection, Hartford, Connecticut, USA.

    Online links:
    Other citation details:
    The Natural Drainage Basins in Connecticut map is published by the State of Connecticut, Department of Environmental Protection, Natural Resources Center in cooperation with the U.S. Geological Survey. The map was funded in part by the Water Resources Council. Map scale 1:125,000.

  2. What geographic area does the data set cover?

    Bounding coordinates:
    West: -73.760405
    East: -71.465712
    North: 42.603944
    South: 40.936173

  3. What does it look like?

    http://www.cteco.uconn.edu/metadata/dep/browsegraphic/localbasinfullview.gif (GIF)
    Full view of Connecticut Local Drainage Basins - Local Drainage Basin line features are symbolized by the Drainage Basins Divide (DIVIDE) attribute to illustrate the basin hierarchy.

    http://www.cteco.uconn.edu/metadata/dep/browsegraphic/localbasindetailview.gif (GIF)
    Detail view of Connecticut Local Drainage Basins - Local Drainage Basins polygon features are labeled with the 7-digit local basin number. Local Drainage Basin line features are symbolized by the Drainage Basins Divide (DIVIDE) attribute to illustrate the basin hierarchy. Watercourses are shown in the background.

    http://www.cteco.uconn.edu/metadata/dep/browsegraphic/localbasinmainstem.gif (GIF)
    Detail view of Local Basin main stem - Main stem basins for larger rivers and streams are denoted with two zeros (00) in columns 6 and 7. These local main stem basins receive flow from upstream tributaries.

  4. Does the data set describe conditions during a particular time period?

    Calendar date: 1988
    Currentness reference:
    publication date

  5. What is the general form of this data set?

    Geospatial data presentation form: vector digital data

  6. How does the data set represent geographic features?

    1. How are geographic features stored in the data set?

      Indirect spatial reference:
      Connecticut DEP Major Basin Number, Regional Basin Number, Subregional Basin Number, Local Basin Number, Basin Number

      This is a Vector data set. It contains the following vector data types (SDTS terminology):
      • String (8663)

    2. What coordinate system is used to represent geographic features?

      The map projection used is Lambert Conformal Conic.

      Projection parameters:
      Lambert Conformal Conic
      Standard parallel: 41.200000
      Standard parallel: 41.866667
      Longitude of central meridian: -72.750000
      Latitude of projection origin: 40.833333
      False easting: 999999.999996
      False northing: 499999.999998

      Planar coordinates are encoded using coordinate pair.
      Abscissae (x-coordinates) are specified to the nearest 0.000250.
      Ordinates (y-coordinates) are specified to the nearest 0.000250.
      Planar coordinates are specified in survey feet.

      The horizontal datum used is North American Datum of 1983.
      The ellipsoid used is Geodetic Reference System 80.
      The semi-major axis of the ellipsoid used is 6378137.000000.
      The flattening of the ellipsoid used is 1/298.257222.

      Vertical coordinate system definition:
      Altitude system definition:
      Altitude resolution: 1.000000
      Altitude encoding method: Explicit elevation coordinate included with horizontal coordinates

  7. How does the data set describe geographic features?

    Connecticut Local Drainage Basin Line
    Drainage basin linear features outline all drainage basin polygon features. These line features typically represent drainage basin divides between major, regional, subregional, local, stream reach, and smaller lake impoundment basins. However, some features are not true drainage basin divides. For example, line features that coincide with the coastline enclose coastal basins that drain into Long Island Sound. These line features that follow the coast are encoded as shoreline features. (Source: State of Connecticut, Department of Environmental Protection)

    OBJECTID
    Internal feature number. (Source: ESRI)
                      

    Sequential unique whole numbers that are automatically generated.

    DBARC_COD
    Drainage Basin Arc Code - A numeric code that describes the type of drainage basin divide. There are 9 drainage basins arc code values, one for each type of feature. For example, a drainage basin line feature that forms the boundary between two Major drainage basins has a Drainage Basin Arc Code value of 1 (DBARC_COD = 1); a drainage basin line feature that forms the boundary between two Regional drainage basins in the same Major basin has a Drainage Basin Arc Code value of 2 (DBARC_COD = 2); a drainage basin line feature that forms the boundary between two Subregional drainage basins in the same Regional basin has a Drainage Basin Arc Code value of 3 (DBARC_COD = 3); and so on. Not all linear features represent true drainage basin divides between drainage basins. Some line feature types are introduced in order to close certain polygon features along the data limit or along the coast. For example, line features that are not true drainage basin divides or features that follow the geometry of the (coastal) shoreline have DBARC_COD values of 0 and 8, respectively. When symbolizing drainage basins arc features on DBARC_COD or DIVIDE values, be sure to exclude features not intended to be shown on the map by using the following layer definition query: DBARC_COD > 0. (Source: State of Connecticut, Department of Environmental Protection)
                      

    ValueDefinition
    0
    Not a drainage basin divide
    1
    Major drainage basin divide
    2
    Regional drainage basin divide
    3
    Subregional drainage basin divide
    4
    Local drainage basin divide
    5
    Stream reach basin divide
    6
    Lake impoundment basin divide
    8
    Shoreline - Not a true drainage divide. This line feature is coincident with the shoreline and introduced to close coastal basins draining into Long Island Sound.
    9
    State Boundary
    10
    Water diversion point divide

    DIVIDE
    Drainage Basin Divide - Text values that correspond to numeric DBARC_COD attribute values. DIVIDE is the English language equivalent of (decodes) the DBARC_COD field. When symbolizing drainage basins arc features on DBARC_COD or DIVIDE values, be sure to exclude features not intended to be shown on the map by using the following layer definition query: DIVIDE <> "Not a drainage basin divide". (Source: State of Connecticut, Department of Environmental Protection)
                      

    See Enumerated Domain Value Definitions for DBARC_COD attribute.

    AV_LEGEND
    ArcView Legend. A text field for symbolizing the different types of drainage basin divides on a map. The AV_LEGEND attribute classifies basin boundary features into the same categories as DBARC_COD and DIVIDE. It is included for convenience. Unlike the IMS_LEGEND attribute, it does not condense features into broader categories. When symbolizing drainage basins arc features on AV_LEGEND values, be sure to exclude features not intended to be shown on the map by using the following layer definition query: AV_LEGEND <> "No Show". (Source: State of Connecticut, Department of Environmental Protection)
                      

    ValueDefinition
    Lake Impoundment
    This category includes DBARC_COD value 6
    Local
    This category includes DBARC_COD value 4
    Major
    This category includes DBARC_COD value 1
    No Show
    This category includes DBARC_COD value 0
    Regional
    This category includes DBARC_COD value 2
    Shoreline
    This category includes DBARC_COD value 8
    Stream Reach
    This category includes DBARC_COD value 5
    Subregional
    This category includes DBARC_COD value 3
    Water Diversion
    This category includes DBARC_COD value 10

    IMS_LEGEND
    Internet Mapping Software Legend - A text field used to classify and symbolize basin boundary features into broad categories, more suitable for use with Internet mapping applications. The IMS_LEGEND attribute condenses the 9 drainage basin line feature types (DBARC_COD values) into 6 broader categories (Major, Regional, Subregional, Local, Shoreline, and No Show). When symbolizing drainage basins arc features on IMS_LEGEND values, be sure to exclude features not intended to be shown on the map by using the following layer definition query: IMS_LEGEND <> "No Show". (Source: State of Connecticut, Department of Environmental Protection)
                      

    ValueDefinition
    Local
    This category includes DBARC_COD value 4
    Major
    This category includes DBARC_COD value 1
    No Show
    This category includes DBARC_COD values 0, 5, 6, and 10
    Regional
    This category includes DBARC_COD value 2
    Shoreline
    This category includes DBARC_COD value 8
    Subregional
    This category includes DBARC_COD value 3

    LENGTH_MI
    Calculated length of feature in miles. Note, LENGTH_MI values are not automatically updated after modifying feature geometry (shape). Values must be recalculated after features are edited, simplified, generalized, clipped, dissolved, etc. (Source: State of Connecticut, Department of Environmental Protection)
                      

    Numeric value

    SHAPE
    Feature geometry. (Source: ESRI)
                      

    Coordinates defining the features.

    SHAPE.len
    Entity and attribute overview:
    Drainage basin information is comprised of a set of polygon and line features that together describe different types of drainage basins and drainage basin divides.  
    
    Part 1 - Drainage Basin Polygon Features
    
    Information encoded for drainage basin polygon features generally includes drainage basin number and name. Below is a brief explanation of the drainage basin identification number. Use the BASIN_NO attribute to uniquely identify drainage basins. The BASIN_NO is a unique number assigned to each polygon feature. However, in a few instances, two adjacent basin polygon features are assigned the same BASIN_NO when separated by a drainage basin line feature encoded as a Water diversion point divide (DBARC_COD = 10).
    
    Basin Numbers:
    
    4 = Major drainage basin number, MBAS_NO (column 1)
    43 = Regional drainage basin number, RBAS_NO (columns 1-2)
    4302 = Subregional drainage basin number, SBAS_NO (columns 1-4)
    4302-04 = Local drainage basin number, LBAS_NO (columns 1-7)
    4302-04-1-R12 = Basin drainage identification number, BASIN_NO (columns 1-13)
    
    Stream Order (column 9):
    
    4304-00-1 = Stream order value of 1 represents a headwater basin.
    4304-00-2 = Stream order value > 1 denotes the complexity of the drainage basin morphology.
    
    Mapping Status Element (column 10):
    
    4302-00-2- = Ending with minus sign (-) denotes detail mapping at 1:24,000 scale for entire basin.
    
    4302-00-2+ = Ending with plus sign (+) denotes detailed mapping not performed at 1:24,000 scale for the entire drainage basin. The Stream Order value will not reflect the complexity of the drainage basin morphology.
    
    4302-00-1* = Ending with asterisk sign (*) denotes a headwater basin containing a delineated impoundment into which a delineated drainage basin outlets.
    
    Reach-Impoundment Identifier (column11) and Number (column 12-13):
    
    4302-00-1-L1 = The value for the Reach-Impoundment Identifier for an impounment basin is L (for lake). It is followed by the Reach-Impoundment Number (1).
    
    4302-04-1-R12 = The value for the Reach-Impoundment Identifier for a stream reach basin is R (for reach). It is followed the Reach-Impoundment Number (12).
    
    Part 2 - Drainage Basin Divide Line Features
    
    Information encoded for line features categorizes drainage basin divides (boundaries) for cartographic purposes. Use the AV_LEGEND or IMS_LEGEND attribute to classify and symbolize boundary lines on a map. The AV_LEGEND attribute classifies basin boundary features into the same categories as DBARC_COD and DIVIDE. It is included for convenience. Unlike the IMS_LEGEND attribute, it does not condense features into broader categories. When symbolizing drainage basins arc features on AV_LEGEND values, be sure to exclude features not intended to be shown on the map by using the following layer definition query: AV_LEGEND <> "No Show". The IMS_LEGEND attribute condenses the 9 drainage basin line feature types (DBARC_COD values) into 6 broader categories (Major, Regional, Subregional, Local, Shoreline, and No Show). When symbolizing drainage basins arc features on IMS_LEGEND values, be sure to exclude features not intended to be shown on the map by using the following layer definition query: IMS_LEGEND <> "No Show". Use the AREA_SQMI and ACREAGE attributes to determine drainage basin polygon feature size. These values reflect the area of the respective polygon feature. They do not reflect the cumulative (upstream) drainage area for each basin. Note, ACREAGE and AREA_SQMI values are not automatically updated after modifying feature geometry (shape). These values must be recalculated after features are edited, simplified, generalized, clipped, dissolved, etc.
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Who produced the data set?

  1. Who are the originators of the data set? (may include formal authors, digital compilers, and editors)


  2. Who also contributed to the data set?

    Tom Nosal, State of Connecticut, Department of Environmental Protection, for the final compilation and delineation of 1:24,000-scale drainage basin boundaries, assignment of drainage basin numbers, and conversion to digitial format. Basin boundaries were manually delineated at 1:24,000-scale by visually interpreting the 10 feet contour elevation lines and waterbody features appearing on 1:24,000-scale 7.5 minute USGS topographic quadrangle maps for Connecticut published between 1969 and 1984. The metadata abstract includes a brief description of a drainage basin obtained from material written by Jim Murphy in an article entitled Reading the Landscape published in the Citizen's Bulletin, a CT DEP monthy magazine.

  3. To whom should users address questions about the data?

    Tom Nosal
    State of Connecticut, Department of Environmental Protection
    79 Elm Street
    Hartford, Connecticut 06106-5127
    USA

    860-424-3540 (voice)
    860-424-4058 (FAX)
    dep.gisdata@ct.gov
    Hours of Service: Monday to Friday, 08:30 to 16:30 Eastern Standard Time
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Why was the data set created?

The polygon features define the contributing drainage area for individual reservoirs, lakes, ponds and river and stream reaches in Connecticut. These are hydrologic land units where precipitation is collected. Rain falling in a basin may take two courses. It may both run over the land and quickly enter surface watercourses, or it may soak into the ground moving through the earth until it surfaces at a wetland or stream. In an undisturbed natural drainage basin, the surface and ground water arrive as precipitation and leave either by evaporation or as surface runoff at the basin's outlet. A basin is a self-contained hydrologic system, with a clearly defined water budget and cycle. The amount of water that flows into the basins equals the amount that leaves. A drainage divide is the topographic barrier along a ridge or line of hilltops separating adjacent drainage basins. For example, rain or snow melt draining down one side of a hill generally will flow into a different basin and stream than water draining down the other side of the hill. These hillsides are separated by a drainage divided that follows nearby hilltops and ridge lines.

Use these basin data to identify where rainfall flows over land and downstream to a particular watercourse. Use these data to categorize and tabulate information according to drainage basin by identifying the local basin number for individual reservoir, lake, pond, stream reach, or location of interest. Due to the hierarchical nature of the basin numbering system, a database that records the 7-digit local basin number for individual geographic locations of interest will support tabulations by major, regional, subregional, and local basin as well as document the unique 7-digit local basin number. To identify either all upstream basins draining to a particular location or all downstream basins flowing from a particular location, refer to the Gazetteer of Drainage Basin Areas of Connecticut, Nosal, 1977, CT DEP Water Resources Bulletin 45, for the hydrologic sequence, headwater to outfall, of drainage basins available at http://cteco.uconn.edu/docs/wrb/wrb45_gazetteer_of_drainage_areas_of_connecticut.pdf

Not intended for maps printed at map scales greater or more detailed than 1:24,000 scale (1 inch = 2,000 feet.). Not intended for analysis with other digital data compiled at scales greater than or more detailed than 1:24,000 scale. Use these data with 1:24,000-scale hydrography data also available from the State of Connecticut, Department of Environmental Protection.

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How was the data set created?

  1. Where did the data come from?

    Source 1 - Source Materials (source 1 of 3)

    State of Connecticut, Department of Environmental Protection, Unpublished Material, drainage basin compilation sheets.

    Type of source media: stable-base material
    Source scale denominator: 24000
    Source contribution:
    Basins compiled on 1:24,000-scale 7.5 minute USGS quadrangle area mylar overlays.

    Source 2 - Drainage Basins (source 2 of 3)

    State of Connecticut, Department of Environmental Protection, 1988, Connecticut Drainage Basins: State of Connecticut, Department of Environmental Protection, Hartford, Connecticut USA.

    Online links:
    Other citation details:
    The State of Connecticut, Department of Environmental Protection is the collector of the data (compiler), the creator and maintainer of the data layer (editor), and producer (publisher) of this information for use. Data compiled and digitized from the 1:24,000-scale compilation sheets for the 1:125,000-scale Natural Drainage Basins in Connecticut Map, McElroy, 1981. The 2006 Edition includes the same basin features originally published in 1988 with some minor corrections and improvements made to feature attribute information. Previously undetected errors have been corrected and are included in this 2006 edition. This data is not updated. Source map scale is 1:24,000.

    Type of source media: disc
    Source scale denominator: 24000
    Source contribution:
    Connecticut Drainage Basins is in ArcInfo Coverage format having both polygon and line features. The name of the ArcInfo Coverage is BASIN.

    Source 3 - Local Drainage Basins (source 3 of 3)

    State of Connecticut, Department of Environmental Protection, 1988, Connecticut Local Basins: State of Connecticut, Department of Environmental Protection, Hartford, Connecticut, USA.

    Online links:
    Other citation details:
    The State of Connecticut, Department of Environmental Protection is the collector of the data (compiler), the creator and maintainer of the data layer (editor), and producer (publisher) of this information for use. Data compiled and digitized from the 1:24,000-scale compilation sheets for the 1:125,000-scale Natural Drainage Basins in Connecticut Map, McElroy, 1981. The 2006 Edition includes the same basin features originally published in 1988 with some minor corrections and improvements made to feature attribute information. Previously undetected errors have been corrected and are included in this 2006 edition. This data is not updated. Source map scale is 1:24,000.

    Type of source media: disc
    Source scale denominator: 24000
    Source contribution:
    Connecticut Local Drainage Basins is in ArcInfo Coverage format having both polygon and line features. The name of the ArcInfo Coverage is LBASIN. These polygon and line feature data were subsequently converted to geodatabase feature format and named LOCAL_BASIN_POLY and LOCAL_BASIN_LINE, respectively.

  2. What changes have been made?

    Date: 1988 (change 1 of 2)
    Feature digitizing and attribution (digitizing tablet method) - Using ESRI ArcInfo software, basin boundary line features were digitized by registering the individual compilation sheets 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. ArcInfo software compared the values of the digitized coordinates with the actual (true) values for the quadrangle corner (tic) features. The Root Mean Square (RMS) error generated by the ArcInfo software indicated the amount of error involved in transforming coordinates from the registered map to the digital layer. RMS errors higher than 0.004 were not acceptable and required re-registering the source map by digitizing the tic locations again. With a correct registration, basins boundaries features were manually digitized off the source map. Where necessary, additional minor corrections (edits) to feature geometry were manually digitized on the screen (heads-up digitizing) at display scales greater than 1:24,000.  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 hard copy paper maps, and comparing this information to the orginal source data. These check plot maps were printed at the same scale as the source maps in order to visually inspect digitizing quality and the assignment of attribute values. 
    
    Individual quadrangle level basin boundary coverages were appended and edgematched along quadrangle boundaries to create a statewide layer in ArcInfo Coverage format having both polygon and line features. Polygon label points were created and assigned BASIN_NO values that uniquely identified each polygon feature. Most other related polygon and line feature attributes were assigned through automated procedures based on the format and hierarchical nature of the BASIN_NO value. Four additional fields (MBAS_NO, RBAS_NO, SBAS_NO, LBAS_NO) were added and populated based on the first, first 2, first 4, and first 7 columns of the BASIN_NO attribute. The MAJOR, REGIONAL, and SUBREGION attributes store drainage basin names based on MBAS_NO, RBAS_NO, SBAS_NO values, respectively. Basin names were attributed by joining basin name lookup tables to the polygon features base on MBAS_NO, RBAS_NO, SBAS_NO key values and populating the corresponding fields. These basin names are from the Natural Drainage Basins in Connecticut map, McElroy, 1981. The AREA_SQMI (area in square miles) and ACREAGE (area in acres) field were automatically calculated for each polygon feature based on computer generated feature area in square feet. The GAZRECNO attribute was manually assigned to each basin polygon feature.
    
    For line features, the DBARC_COD attribute was populated through a combination of automated and manual processes that compared the BASIN_NO attribute value of the polygon on each side of the line. For example, if the two polygons are in different major basins (MBAS_NO on the left <> MBAS_NO on the right), then the line feature represents a Major basin drainage divide and is assigned a DBARC_COD value of 1. If the left and right polygons are in the same Major basins but in different regional basins (RBAS_NO on the left <> RBAS_NO on the right), the line feature is a Regional basin drainage divide and is assigned a DBARC_COD value of 2, and so on. DIVIDE is the English language equivalent of (decodes) the DBARC_COD attribute value and was populated by joining a lookup table to the line features instead of manually attributing these values for each line feature. AV_LEGEND and IMS_LEGEND values were also attributed through table joins.

    Person responsible for change:
    Tom Nosal
    State of Connecticut, Department of Environmental Protection
    79 Elm Street
    Hartford, Connecticut 06106
    USA

    806-424-3540 (voice)
    860-424-4058 (FAX)
    Hours of Service: Mondy to Friday, 8:30 to 16:30 Eastern Standard Time

    Data sources used in this process:
    • Source 1 - Source Materials

    Data sources produced in this process:
    • Source 2 - Drainage Basins

    Date: 1988 (change 2 of 2)
    Create Local Drainage Basins -  Using ArcInfo Workstation software, removed the BASIN_NO polygon feature attribute, calculated the ACREAGE and AREA_SQMI polygon attributes to zero, and dissolved polygon features on the remaining LBAS_NO, SBAS_NO, RBAS_NO, MBAS_NO, SUBREGIONAL, REGIONAL, and MAJOR attribute values to create local drainage basin polygon features. Using the ArcInfo Dissolve command, this step merged the smaller basin polygons into the larger local basin polygon features. Line features were preserved as part of the dissolve process and were merged using the ArcInfo Unsplit command afterwards. The ACREAGE and AREA_SQMI attributes were recalculated based on the new feature geometry, and ArcInfo coveage topology was re-established with the Build command.

    Person responsible for change:
    Tom Nosal, Howie Sternberg
    State of Connecticut, Department of Environmental Protection
    79 Elm Street
    Hartford, Connecticut 06106
    USA

    860-424-3540 (voice)
    860-424-4058 (FAX)
    Hours of Service: Mondy to Friday, 8:30 to 16:30 Eastern Standard Time

    Data sources used in this process:
    • Source 2 - Drainage Basins

    Data sources produced in this process:
    • Source 3 - Local Drainage Basins

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How reliable are the data; what problems remain in the data set?

  1. How well have the observations been checked?

    The Drainage Basins layer retains the feature types and information identified on the 1:24,000-scale compilation sheets for the Natural Drainage Basins in Connecticut map, McElroy, 1981. All attributes have valid values. Values are within defined domains. There are no duplicate LBASIN_NO values except where expected (see definition of LBASIN_NO attribute).
    
    The LBASIN_NO is derived from the first 7-digits of BASIN_NO so the accuracy of the LBASIN_NO is dependent on that for the BASIN_NO. For polygon features, the accuracy test for the BASIN_NO attribute values was conducted by visually comparing the basin number information depicted on the source Mylar overlays with 1:24,000-scale check plots or interactive displays of the digital data on a computer graphic system. These check plot maps and computer displays labeled polygon features with BASIN_NO values and differentiated line features based on DBARC_COD values for comparison with the original source Mylars. Subsequently, four additional fields (MBAS_NO, RBAS_NO, SBAS_NO, LBAS_NO) were added and populated based on the first, first 2, first 4, and first 7 columns of the BASIN_NO attribute. The MAJOR, REGIONAL, and SUBREGION attributes store drainage basin names based on MBAS_NO, RBAS_NO, SBAS_NO values, respectively. Basin names were attributed by joining basin name lookup tables to the polygon features base on MBAS_NO, RBAS_NO, SBAS_NO key values and populating the corresponding fields. These basin names are from the Natural Drainage Basins in Connecticut map, McElroy, 1981. The AREA_SQMI (area in square miles) and ACREAGE (area in acres) field were automatically calculated for each polygon feature based on computer generated feature area in square feet.
    
    For line features, the DBARC_COD attribute was populated through a combination of automated and manual processes that compared the BASIN_NO attribute value of the polygon on each side of the line. For example, if the two polygons are in different major basins (MBAS_NO on the left <> MBAS_NO on the right), then the line feature represents a Major basin drainage divide and is assigned a DBARC_COD value of 1. If the left and right polygons are in the same Major basins but in different regional basins (RBAS_NO on the left <> RBAS_NO on the right), the line feature is a Regional basin drainage divide and is assigned a DBARC_COD value of 2, and so on. DIVIDE is the English language equivalent of (decodes) the DBARC_COD attribute value and was populated by joining a lookup table to the line features instead of manually attributing these values for each line feature. AV_LEGEND and IMS_LEGEND values were also attributed through table joins.

  2. How accurate are the geographic locations?

    The horizontal positional accuracy of this data complies with the United States National Map Accuracy Standards for 1:24,000 scale maps. According to this standard, not more than 10 percent of the locations tested are to be in error by more than 1/50 inch (40 feet) measured on the publication scale of a USGS 7.5 minute topographic quadrangle map.
    
    Drainage basin boundaries were interpolated from 10 FT elevation contours and surface water body (hydrography) information published on a set of USGS 1:24,000-scale, 7.5-minute topographic quadrangle maps that cover the State of Connecticut. Natural drainage basin boundaries were manually delineated by interpolating elevation and water body information found on topographic quadrangle maps published by the USGS between 1962 and 1984.

  3. How accurate are the heights or depths?

  4. Where are the gaps in the data? What is missing?

    The data reflects the content of the data source, which is a set of 1:24,000 scale mylar sheets used to compile and publish the 1:125,000-scale Drainage Basins in Connecticut Map, McElroy, 1982. All major, regional, subregional, local and smaller basin divides were digitized from these 1:24,000-scale mylar compilation sheets. This data is not updated.

  5. How consistent are the relationships among the observations, including topology?

    Polygon features conform to the following topological rules. Polygons are single part. There are no duplicate polygons. Polygons do not self overlap. Polygons do not overlap other polygons. Lines are single part. Line features conform to the following topological rules. There are no duplicate lines. Lines do not self overlap. Lines do not overlap other lines. Lines intersect only at nodes, and nodes anchor the ends of all lines. Lines do not overshoot or undershoot other lines they are supposed to meet and intersect. In general, there are no duplicate features, unresolved intersections, overshooting lines, open polygons, sliver polygons, or unlabeled (unattributed) polygons. The tests of logical consistency were performed by the State of Connecticut using ESRI ArcInfo software to maintain feature topology in ArcInfo coverage format. The data is topologically clean. The ArcInfo Clean function was repeatedly used following edits to verify topology and enforce a minimum distance between vertices of 4 feet (fuzzy tolerance) and a minimum allowed overshoot length of 0 feet (dangle length).

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How can someone get a copy of the data set?

Are there legal restrictions on access or use of the data?

Access constraints: None. The data is in the public domain and may be redistributed.
Use constraints:
No restrictions or legal prerequisites for using the data. The data is suitable for use at appropriate scale, and is not intended for maps printed at scales greater or more detailed than 1:24,000 scale (1 inch = 2,000 feet). 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. For example, include the following data source description when printing this layer on a map: Basins - From the Local Drainage Basins layer, compiled and published by CT DEP. Source map scale is 1:24,000.

Distributor 1 of 1

  1. Who distributes the data set?

    State of Connecticut, Department of Enviromental Protection
    79 Elm Street
    Hartford, Connecticut 06106-5127
    USA

    860-424-3540 (voice)
    860-424-4058 (FAX)
    dep.gisdata@ct.gov
    Hours of Service: Monday to Friday, 08:30 to 16:30 Eastern Standard Time

  2. What's the catalog number I need to order this data set?

    Connecticut Local Drainage Basins Line

  3. What legal disclaimers am I supposed to read?

    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.

  4. How can I download or order the data?

    • Availability in digital form:


    • Data format:
      in format Shapefile, Feature Class, ArcInfo Coverage (version ArcGIS)
      Network links:http://www.ct.gov/deep

    • Cost to order the data: An online copy of the data may be accessed without charge.


  5. Is there some other way to get the data?

    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.

  6. What hardware or software do I need in order to use the data set?

    Geographic information sytem (GIS), computer-aided drawing or other mapping software is necessary to display, view and access the information.

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Who wrote the metadata?

Dates:
Last modified: 20120125

Metadata author:
Tom Nosal, Howie Sternberg
State of Connecticut, Department of Environmental Protection
79 Elm Street
Hartford, Connecticut 06106-5127
USA

860-424-3540 (voice)
860-424-4058 (FAX)
dep.gisdata@ct.gov
Hours of Service: Monday to Friday, 08:30 to 16:30 Eastern Standard Time

Metadata standard:
FGDC Content Standards for Digital Geospatial Metadata(FGDC-STD-001-1998)

Metadata extensions used:
  • http://www.esri.com/metadata/esriprof80.html

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