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.
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).
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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)
Internal feature number. (Source: ESRI)
Local Drainage Basin Number - This number defines the Local drainage basin and is the first 7 digits of the 13-digit drainage basin identification number (BASIN_NO). The first digit corresponds to the Major basin number (MBAS_NO). The first 2 digits represent the Regional basin number (RBAS_NO). The first 4 digits represent the Subregional basin number (SBAS_NO). All Local basins in the same Major, Regional, Subregional, and Local basin have the same first, first 2, and first 4 digits, respectively. A Local drainage basin number ending in "00" defines the main-stem basin for the corresponding Subregional drainage basin. For example, Local basin 4300-00 is the main-stem basin for Subregional basin 4300, Local basin 4301-00 is the main-stem basin for Subregional basin 4301, and so on. Unlike Major, Regional, and Subregional basins, Local drainage basins are not named after the river or stream drainage area they represent. (Source: State of Connecticut, Department of Environmental Protection)
Subregional Drainage Basin Number - This number defines the Subregional drainage basin and is the first 4 digits of the 13-digit drainage basin identification number (BASIN_NO). The first digit corresponds to the Major basin number (MBAS_NO) and the first 2 digits represent the Regional basin number (RBAS_NO). All Subregional basins in the same Major and Regional basin have the same first and first 2 digits, respectively. A Subregional drainage basin number ending in "00" defines the main-stem basin for the corresponding Regional drainage basin. For example, Subregional basin 4300 is the main-stem basin for Regional basin 43. These main-stem Subregional basins are usually named after the corresponding Regional basin. (Source: State of Connecticut, Department of Environmental Protection)
| Value | Definition |
|---|---|
| 1000 | Pawcatuck River |
| 1001 | Wyassup Brook |
| 1002 | Green Fall River |
| 1003 | Ashaway River |
| 1004 | Shunock River |
| 1100 | Wood River |
| 1101 | Brushy Brook |
| 2000 | Southeast Shoreline |
| 2101 | Anguilla Brook |
| 2102 | Copps Brook |
| 2103 | Williams Brook |
| 2104 | Whitford Brook |
| 2105 | Haleys Brook |
| 2106 | Mystic River |
| 2107 | Great Brook |
| 2201 | Jordan Brook |
| 2202 | Latimer Brook |
| 2203 | Oil Mill Brook |
| 2204 | Niantic River |
| 2205 | Pattagansett River |
| 2206 | Bride Brook |
| 2207 | Fourmile River |
| 3000 | Thames River |
| 3001 | Trading Cove Brook |
| 3002 | Shewville Brook |
| 3003 | Poquetanuck Brook |
| 3004 | Oxoboxo Brook |
| 3005 | Stony Brook |
| 3006 | Hunts Brook |
| 3100 | Willimantic River |
| 3101 | Edson Brook |
| 3102 | Middle River |
| 3103 | Furnace Brook |
| 3104 | Roaring Brook |
| 3105 | Mill Brook |
| 3106 | Skungamaug River |
| 3107 | Burnap Brook |
| 3108 | Hop River |
| 3109 | Giffords Brook |
| 3110 | Tenmile River |
| 3200 | Natchaug River |
| 3201 | Bungee Brook |
| 3202 | Still River |
| 3203 | Bigelow Brook |
| 3204 | Stonehouse Brook |
| 3205 | Squaw Hollow Brook |
| 3206 | Mount Hope River |
| 3207 | Fenton River |
| 3208 | Sawmill Brook |
| 3300 | French River |
| 3301 | Mill Brook |
| 3400 | Fivemile River |
| 3401 | Rocky Brook |
| 3402 | Mary Brown Brook |
| 3403 | Cady Brook |
| 3404 | Whetstone Brook |
| 3500 | Moosup River |
| 3501 | Quanduck Brook |
| 3502 | Snake Meadow Brook |
| 3503 | Ekonk Brook |
| 3600 | Pachaug River |
| 3601 | Great Meadow Brook |
| 3602 | Mount Misery Brook |
| 3603 | Denison Brook |
| 3604 | Myron Kinney Brook |
| 3605 | Billings Brook |
| 3700 | Quinebaug River |
| 3701 | Hamilton Reservoir Brook |
| 3702 | Breakneck Brook |
| 3703 | Hatchet Brook |
| 3704 | Cohasse Brook |
| 3705 | Lebanon Brook |
| 3706 | English Neighborhood Brook |
| 3707 | Mill Brook |
| 3708 | Little River |
| 3709 | Wappoquia Brook |
| 3710 | Mashamoquet Brook |
| 3711 | Blackwell Brook |
| 3712 | Fry Brook |
| 3713 | Mill Brook |
| 3714 | Kitt Brook |
| 3715 | Cory Brook |
| 3716 | Broad Brook |
| 3717 | Choate Brook |
| 3800 | Shetucket River |
| 3801 | Indian Hollow Brook |
| 3802 | Beaver Brook |
| 3803 | Merrick Brook |
| 3804 | Beaver Brook |
| 3805 | Little River |
| 3900 | Yantic River |
| 3901 | Exeter Brook |
| 3902 | Bartlett Brook |
| 3903 | Sherman Brook |
| 3904 | Deep River |
| 3905 | Pease Brook |
| 3906 | Gardner Brook |
| 3907 | Susquetonscut Brook |
| 4000 | Connecticut River |
| 4001 | Great Brook |
| 4002 | Threemile Brook |
| 4003 | Freshwater Brook |
| 4004 | Podunk River |
| 4005 | Folly Brook |
| 4006 | Salmon Brook |
| 4007 | Hubbard Brook |
| 4008 | Cold Brook |
| 4009 | Roaring Brook |
| 4010 | Goff Brook |
| 4011 | Reservoir Brook |
| 4012 | Carr Brook |
| 4013 | Sumner Brook |
| 4014 | Higganum Creek |
| 4015 | Mill Creek |
| 4016 | Whalebone Creek |
| 4017 | Chester Creek |
| 4018 | Deep River |
| 4019 | Falls River |
| 4020 | Lieutenant River |
| 4021 | Black Hall River |
| 4100 | Stony Brook |
| 4101 | Muddy Brook |
| 4200 | Scantic River |
| 4201 | Watchaug Brook |
| 4202 | Gillettes Brook |
| 4203 | Gulf Stream |
| 4204 | Abbey Brook |
| 4205 | Buckhorn Brook |
| 4206 | Broad Brook |
| 4207 | Ketch Brook |
| 4300 | Farmington River |
| 4301 | Slocum Brook |
| 4302 | Mad River |
| 4303 | Still River |
| 4304 | Sandy Brook |
| 4305 | Morgan Brook |
| 4306 | Valley Brook |
| 4307 | Hubbard Brook |
| 4308 | East Branch Farmington River |
| 4309 | Cherry Brook |
| 4310 | Nepaug River |
| 4311 | Burlington Brook |
| 4312 | Roaring Brook |
| 4313 | Poland River |
| 4314 | Copper Mine Brook |
| 4315 | Pequabuck River |
| 4316 | Thompson Brook |
| 4317 | Nod Brook |
| 4318 | Hop Brook |
| 4319 | West Branch Salmon Brook |
| 4320 | Salmon Brook |
| 4321 | Mill Brook |
| 4400 | Park River |
| 4401 | Bass Brook |
| 4402 | Piper Brook |
| 4403 | Trout Brook |
| 4404 | North Branch Park River |
| 4500 | Hockanum River |
| 4501 | Charters Brook |
| 4502 | Marsh Brook |
| 4503 | Tankerhoosen River |
| 4504 | South Fork Hockanum River |
| 4600 | Mattabesset River |
| 4601 | Belcher Brook |
| 4602 | Willow Brook |
| 4603 | Webster Brook |
| 4604 | Sawmill Brook |
| 4605 | Allyn Brook |
| 4606 | Sawmill Brook |
| 4607 | Coginchaug River |
| 4700 | Salmon River |
| 4701 | Raymond Brook |
| 4702 | Judd Brook |
| 4703 | Meadow Brook |
| 4704 | Pine Brook |
| 4705 | Jeremy River |
| 4706 | Fawn Brook |
| 4707 | Blackledge River |
| 4708 | Dickinson Creek |
| 4709 | Pine Brook |
| 4710 | Moodus River |
| 4800 | Eightmile River |
| 4801 | Harris Brook |
| 4802 | East Branch Eightmile River |
| 4803 | Beaver Brook |
| 5000 | South Central Shoreline |
| 5101 | Oyster River |
| 5102 | Patchogue River |
| 5103 | Menunketesuck River |
| 5104 | Indian River |
| 5105 | Chatfield Hollow Brook |
| 5106 | Hammonasset River |
| 5107 | Neck River |
| 5108 | East River |
| 5109 | Sluice Creek |
| 5110 | West River |
| 5111 | Branford River |
| 5112 | Farm River |
| 5200 | Quinnipiac River |
| 5201 | Eightmile River |
| 5202 | Tenmile River |
| 5203 | Misery Brook |
| 5204 | Broad Brook |
| 5205 | Sodom Brook |
| 5206 | Harbor Brook |
| 5207 | Wharton Brook |
| 5208 | Muddy River |
| 5301 | Willow Brook |
| 5302 | Mill River |
| 5303 | Sargent River |
| 5304 | Wintergreen Brook |
| 5305 | West River |
| 5306 | Indian River |
| 5307 | Wepawaug River |
| 6000 | Housatonic River |
| 6001 | Sages Ravine Brook |
| 6002 | Schenob Brook |
| 6003 | Andrus Brook |
| 6004 | Konkapot River |
| 6005 | Factory Brook |
| 6006 | Spruce Swamp Creek |
| 6007 | Salmon Creek |
| 6008 | Mill Brook |
| 6009 | Carse Brook |
| 6010 | Furnace Brook |
| 6011 | Guinea Brook |
| 6012 | Kent Falls Brook |
| 6013 | Cobble Brook |
| 6014 | Bog Hollow Brook |
| 6015 | Macedonia Brook |
| 6016 | Womenshenuk Brook |
| 6017 | Morrissey Brook |
| 6018 | Pond Brook |
| 6019 | Deep Brook |
| 6020 | Pootatuck River |
| 6021 | Kettletown Brook |
| 6022 | Halfway River |
| 6023 | Eightmile Brook |
| 6024 | Means Brook |
| 6025 | Farmill River |
| 6026 | Pumpkin Ground Brook |
| 6100 | Blackberry River |
| 6101 | Whiting River |
| 6200 | Hollenbeck River |
| 6201 | Brown Brook |
| 6202 | Wangum Lake Brook |
| 6300 | Tenmile River |
| 6301 | Indian Lake Creek |
| 6302 | Mill Brook |
| 6303 | Webatuck Creek |
| 6304 | Deuel Hollow Brook |
| 6305 | Mill River |
| 6306 | Swamp River |
| 6400 | Lake Candlewood |
| 6401 | Sawmill Brook |
| 6402 | Ball Pond Brook |
| 6500 | West Aspetuck River |
| 6501 | Merryall Brook |
| 6502 | East Aspetuck River |
| 6600 | Still River |
| 6601 | Miry Brook |
| 6602 | Boggs Pond Brook |
| 6603 | Padanaram Brook |
| 6604 | Sympaug Brook |
| 6605 | East Swamp Brook |
| 6606 | Limekiln Brook |
| 6700 | Shepaug River |
| 6701 | Marshepaug River |
| 6702 | West Branch Shepaug River |
| 6703 | West Branch Bantam River |
| 6704 | Butternut Brook |
| 6705 | Bantam River |
| 6706 | Jacks Brook |
| 6800 | Pomperaug River |
| 6801 | East Spring Brook |
| 6802 | Nonewaug River |
| 6803 | Sprain Brook |
| 6804 | Weekeepeemee River |
| 6805 | Hesseky Brook |
| 6806 | Transylvania Brook |
| 6900 | Naugatuck River |
| 6901 | Hall Meadow Brook |
| 6902 | Hart Brook |
| 6903 | Nickel Mine Brook |
| 6904 | West Branch Naugatuck River |
| 6905 | East Branch Naugatuck River |
| 6906 | Spruce Brook |
| 6907 | Rock Brook |
| 6908 | Leadmine Brook |
| 6909 | Northfield Brook |
| 6910 | Branch Brook |
| 6911 | Hancock Brook |
| 6912 | Steele Brook |
| 6913 | Beaver Pond Brook |
| 6914 | Mad River |
| 6915 | Fulling Mill Brook |
| 6916 | Hop Brook |
| 6917 | Long Meadow Pond Brook |
| 6918 | Beacon Hill Brook |
| 6919 | Bladens River |
| 6920 | Little River |
| 7000 | Southwest Shoreline |
| 7101 | Lewis Gut |
| 7102 | Bruce Brook |
| 7103 | Yellow Mill Channel |
| 7104 | Booth Hill Brook |
| 7105 | Pequonnock River |
| 7106 | Ash Creek |
| 7107 | Cricker Brook |
| 7108 | Mill River |
| 7109 | Sasco Brook |
| 7200 | Saugatuck River |
| 7201 | Little River |
| 7202 | Aspetuck River |
| 7203 | West Branch Saugatuck River |
| 7300 | Norwalk River |
| 7301 | Comstock Brook |
| 7302 | Silvermine River |
| 7401 | Fivemile River |
| 7402 | Darien River |
| 7403 | Noroton River |
| 7404 | Mill River |
| 7405 | Rippowam River |
| 7406 | East Branch Mianus River |
| 7407 | Mianus River |
| 7408 | Greenwich Creek |
| 7409 | Horseneck Brook |
| 7410 | East Branch Byram River |
| 7411 | Byram River |
| 7412 | Blind Brook |
| 8000 | Hudson River |
| 8100 | Croton River |
| 8101 | Quaker Brook |
| 8102 | Corner Pond Brook |
| 8103 | East Branch Croton River |
| 8104 | Titicus River |
| 8105 | Waccabuc River |
Subregional Drainage Basin Name - Text values that correspond to numeric SBAS_NO attribute values. SUBREGION is the English language equivalent of (decodes) the SBAS_NO field. (Source: State of Connecticut, Department of Environmental Protection)
Regional Drainage Basin Number - This number defines the Regional drainage basin and is the first 2 digits of the 13-digit drainage basin identification number (BASIN_NO). The first digit corresponds to the Major basin number (MBAS_NO). All Regional basins in the same Major basin have the same first digit. A Regional drainage basin number ending in "0" defines the greater main-stem basin for the corresponding Major drainage basin. For example, Regional basin 40 is the main-stem basin for Major basin 4. These main-stem Regional basins are usually named after the corresponding Major basin. (Source: State of Connecticut, Department of Environmental Protection)
| Value | Definition |
|---|---|
| 10 | Pawcatuck Main Stem |
| 11 | Wood |
| 20 | Southeast Shoreline |
| 21 | Southeast Eastern Complex |
| 22 | Southeast Western Complex |
| 30 | Thames Main Stem |
| 31 | Willimantic |
| 32 | Natchaug |
| 33 | French |
| 34 | Fivemile |
| 35 | Moosup |
| 36 | Pachaug |
| 37 | Quinebaug |
| 38 | Shetucket |
| 39 | Yantic |
| 40 | Connecticut Main Stem |
| 41 | Stony Brook |
| 42 | Scantic |
| 43 | Farmington |
| 44 | Park |
| 45 | Hockanum |
| 46 | Mattabesset |
| 47 | Salmon |
| 48 | Eightmile |
| 50 | South Central Shoreline |
| 51 | South Central Eastern Complex |
| 52 | Quinnipiac |
| 53 | South Central Western Complex |
| 60 | Housatonic Main Stem |
| 61 | Blackberry |
| 62 | Hollenbeck |
| 63 | Tenmile |
| 64 | Candlewood |
| 65 | Aspetuck |
| 66 | Still |
| 67 | Shepaug |
| 68 | Pomperaug |
| 69 | Naugatuck |
| 70 | Southwest Shoreline |
| 71 | Southwest Eastern |
| 72 | Saugatuck |
| 73 | Norwalk |
| 74 | Southwest Western Complex |
| 80 | Hudson Main Stem |
| 81 | Croton |
Regional Drainage Basin Name - Text values that correspond to numeric RBAS_NO attribute values. REGIONAL is the English language equivalent of (decodes) the RBAS_NO field. (Source: State of Connecticut, Department of Environmental Protection)
Major Drainage Basin Number - This number defines the major drainage basin and is the first digit of the 13-digit drainage basin identification number (BASIN_NO). There are 8 Major basins. (Source: State of Connecticut, Department of Environmental Protection)
| Value | Definition |
|---|---|
| 1 | Pawcatuck |
| 2 | Southeast Coast |
| 3 | Thames |
| 4 | Connecticut |
| 5 | South Central Coast |
| 6 | Housatonic |
| 7 | Southwest Coast |
| 8 | Hudson |
Major Drainage Basin Name - Text values that correspond to numeric MBAS_NO attribute values. MAJOR is the English language equivalent of (decodes) the MBAS_NO field. (Source: State of Connecticut, Department of Environmental Protection)
Calculated area of polygon feature in acres. Note, ACREAGE 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)
Calculated area of polygon feature in square miles. Note, AREA_SQMI 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)
Feature geometry. (Source: ESRI)
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.
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.
79 Elm Street
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.
Basins compiled on 1:24,000-scale 7.5 minute USGS quadrangle area mylar overlays.
Connecticut Drainage Basins is in ArcInfo Coverage format having both polygon and line features. The name of the ArcInfo Coverage is BASIN.
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.
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.
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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.
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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.
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.
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.
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).
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.
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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.
| Data format: | in format Shapefile, Feature Class, ArcInfo Coverage (version ArcGIS) |
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| 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.
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