Geographic Data Set: Draft Tidal Wetlands (1974). Distribution Constraints: none Use_Constraints: Not survey quality, tidal wetlands are dynamic and the boundaries may have changed. The resultant coverages do not constitute an official tidal wetlands map. The user of the coverages assumes all responsibility for any action that might result from the use of the coverages. All measurements and positions are approximate. Description: New York State tidal wetlands south of the Tappan Zee Bridge, as of 1974, for tidal wetlands trend analysis. The data have been divided into 4 sections (New York City/Westchester County, Nassau County, Suffolk County west of the towns of Riverhead and Southampton, and Suffolk County from Riverhead and Southampton east) to speed display and query in the MHDB over the network. A single shapefile containing all the data is available from the contact listed below. Available: Regions 1,2,3, geographically representing NYS Marine District from the Tappan Zee bridge on the Hudson River south to southern tip of Staten Island east to and including Fishers Island. Location: web nyctidwet74.shp, nastidwet74.shp, suftidwet74_w.shp, suftidwet74_e.shp Completion or Most Recent Revision Date: November 2005 Type of Data: Polygon shapefile with Attribute Table. Source of Information: An edge matched vector line was digitized in ARC/INFO from mylar maps of the Official New York State Tidal Wetlands Inventory at 1 inch equals 200 feet. These mylars were made by enlarging 1974 color infrared aerial photography at 1 inch equals 1,000 feet and best fitting the enlargement to New York State Department of Transportation maps at a scale of 1 inch equals 2,000 feet. Each map, 2,000m x 2,000m, is identified with a six digit New York Transverse Mercator coordinate (NAD27), e.g. 600-526 (600 is 600,000 and 526 is 4,526,000). The maps were not subject to aerial triangulation. The vector lines were used to build polygons that were coded with the tidal wetlands category. Data from several digitizing projects were combined into a single ARC/INFO coverage and projected from NAD27 to NAD83. The coverage was then split into 4 sections (see Description above), and the sections were converted to shapefiles. Projection and Map Units: NYTM in meters, NAD83 horizontal datum. Spatial_Domain: Bounding_Coordinates: West_Bounding_Coordinate:74.261707547 East_Bounding_Coordinate: 65.853844994 North_Bounding_Coordinate: 41.076208167 South_Bounding_Coordinate: 40.495525783 Attribute Tables: Items (or Fields) in the Polygon Attribute Table Contact: Fred Mushacke NYSDEC Bureau of Marine Resources 205 North Belle Meade Road East Setauket, NY 11733 Phone: 631-444-0465 Fax: 631-444-0472 fmmushac@gw.dec.state.ny.us Documentation Date: 2 December 2005 Distribution_Liability: The resultant coverages do not constitute an official tidal wetlands map. The user of the coverages assumes all responsibility for any action that might result from the use of the coverages. All measurements and positions are approximate. Usage Notes: The digital data do not constitute an official tidal wetlands map. The user of the data assumes all responsibility for any action that might result from the use of the data. All measurements and positions are approximate. The official tidal wetlands inventory maps from which the wetland boundaries were digitized are based on aerial photographs that, though best-fitted to NYSDOT planimetric maps, are nonetheless not ortho-rectified. This, along with shoreline changes that have occurred since 1974 (year of the photography), means that some of the digitized wetland boundaries may not align well with current orthophotography or with other GIS data layers. Some of the wetland boundaries in the digital data do not appear on the official tidal wetlands inventory maps. These include boundaries added to correct errors/omissions identified during digitizing of the maps, and others added in unmapped 2,000m x 2,000m blocks to connect "dangling" boundaries on adjacent mapped blocks. Some wetlands labeled as category FC on the official tidal wetlands inventory maps may be coded as HM or IM in the digital data. The re-coding (done during some of the earlier digitizing efforts) was intended to indicate the dominant vegetation type, since this is what determines the regulatory value of FC wetlands. Although the codes for some of these wetlands were reverted to FC during the final digitizing effort, FC-mapped wetlands coded as HM or IM in the digital data may still exist in the areas of Moriches, Quantuck and Shinnecock Bays, Fishers Island and the Town of East Hampton. When the data are displayed in ArcView 3.3, colors used to symbolize the different wetland categories (particularly those with large and complicated polygons such as LZ and AA) may display inside the wrong polygons when zooming in and out. If in doubt, the Identify tool can be used to determine the correct category as coded in the polygon attributes. Area, Perimeter and Acreage74 fields will not update automatically if polygons are split or otherwise changed in shape. Area and Perimeter can be recalculated using the Avenue script calcapl.ave in c:\esri\av_gis30\arcview\samples\scripts, and Acreage74 can be recalculated as Area * 0.0002471. -------------------------------------------------------------------------------- Attribute Tables -------------------------------------------------------------------------------- Items (or Fields) in the Polygon Attribute Table -------------------------------------------------------------------------------- AREA: Area of the polygon in square meters, as calculated by the ARC/INFO GIS software. PERIMETER: Perimeter of the polygon in meters, as calculated by the ARC/INFO GIS software. ID: Unique number identifying the polygon. TWTYPE74: A numeric code corresponding to the tidal wetlands category; see definitions under the TWCAT74 field. TWCAT74: A two-letter code for the tidal wetlands category. With the exception of AA and HL (see below), these are the codes that are labeled on the 1974 official tidal wetlands inventory maps. Regulated areas (as noted below) are areas that are regulated by law and require a permit review. Management areas (as noted below) are areas that have been identified for management purposes. Management areas are non-tidal areas but may require permit review as adjacent areas or as other protected areas. TWTYPE74 TWCAT74 2010 SM. Coastal Shoals, Bars and Mudflats. Regulated area. The tidal wetland zone that at high tide is covered by saline or fresh tidal waters, at low tide is exposed or is covered by water to a maximum depth of approximately one foot, and is not vegetated. 2020 LZ. Littoral Zone. Regulated Area. The tidal wetland zone that includes all lands under tidal water which are not included in any other category and which are six feet or less under water at mean low tide. Note, however, that portions of some areas labeled as LZ on the official tidal wetlands inventory maps (and in the digital data) are almost certainly more than six feet under water at mean low tide. See 6NYCRR Part 661.4 for more detail. 2030 FC. Formerly Connected. The tidal wetland zone in which normal tidal flow is restricted by man-made causes. Phragmites sp. is the dominant vegetation. 3000 IM. Intertidal Marsh. Regulated Area. The vegetated tidal wetland zone lying generally between average high and low tidal elevation in saline waters. The predominant vegetation in this zone is low marsh cordgrass, Spartina alterniflora. See also Usage Note 4. 3010 FM. Fresh Marsh. Regulated Area. The tidal wetland zone found primarily in the upper tidal limits of riverine systems where significant freshwater inflow dominates the tidal zone. Species normally associated with this zone include narrow leaved cattail, Typha angustifolia; the tall brackish water cordgrass, Spartina pectinata and/or S. cynosuroides; and the more typically emergent fresh water species such as arrow arum, Peltandra; pickerel weed, Pontederia; and cutgrass, Leersia. 4000 HM. High Marsh. Regulated area. The normal uppermost tidal wetland zone usually dominated by salt meadow grass, Spartina patens; and spike grass, Distichlis spicata. This zone is periodically flooded by spring and storm tides and is often vegetated by low vigor, Spartina alterniflora and Seaside lavender, Limonium carolinianum. Upper limits of this zone often include black grass, Juncus gerardii; chairmaker's rush, Scirpus sp; marsh elder, Iva frutescens; and groundsel bush, Baccharis halimifolia. See also Usage Note 4. 5000 AA. Adjacent Area. Regulated area. Adjacent area shall mean those land areas not included in the any of the above categories that are generally not inundated by tidal waters and that extend 300 feet landward of the most landward tidal wetlands boundary (150 feet in New York City) or to an elevation of ten feet. See 6NYCRR Part 661.4 for more detail. Note that AA areas are not explicitly labeled on the tidal wetlands inventory maps. Areas of the tidal wetlands inventory maps not labeled with a tidal wetlands category were assigned a category of AA (Adjacent Area) in the digital data by default. Portions of these AA-coded polygons do not meet the legal definition (per 6NYCRR Part 661.4) of an Adjacent Area. 5010 DS. Dredged Spoil. Regulated area. All areas of fill material. Labeled “ds” on 1974 tidal wetlands inventory maps. 9999 HL. Hole Area includes areas that do not contain tidal wetlands or adjacent area. Management area. These areas, which are not covered by 1974 tidal wetlands inventory maps, represent polygons formed in the digital data by surrounding mapped areas. In some cases, areas that might otherwise have been considered HL had tidal wetland polygons added during digitizing to complete wetlands on adjacent mapped areas. See Usage Note 3. Note also that this category is not included in the default legend that loads with the theme from the MHDB Data Selector. ACREAGE74: Acreage of the polygon calculated by multiplying the AREA field (see above) by 0.0002471. At the 3 decimal places allotted to this item, a few very small polygons have zero acreage.