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r4/HCZ (MapServer)

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Service Description: The Hydrologically Connected Zone (HCZ) mask is a grid file indicating all surface water features, including, lakes, rivers, streams, wetlands, estuaries, and nearshore ocean waters, as mapped in the 1:100,000-scale; plus all contiguous areas that have a wetness index value of 550 or greater. The HCZ is determined using grid analysis to combine surface water features of three datasets. First, the surface water features from the 2011 National Land Cover Database (NLCD). Features included are 'Open Water' (code 11), 'Woody Wetlands' (code 90) and 'Emergent Herbaceous Wetlands' (code 95). Source data used was the NLCD2011 version 1 (see NLCD2011 metadata). Second, the flowline and waterbody features as represented in the catseed grid from the National Hydrography Dataset (NHD) Plus version 2. Source data used was NHD Plus Version 2.1, downloaded October 31, 2012 (see NHD Plus Version 2 metadata). The combination of these two datasets represents surface water and is referred to as the ‘Water Mask’ (see Water Mask metadata). Third, all areas contiguous to surface water that also has a wetness index value of 550 or greater. The wetness index, also known as the compound topographic index (CTI), is a steady state wetness index. It is commonly used to quantify topographic control on hydrological processes (see Wetness Index metadata). The combination of these three datasets represents the HCZ. A cell value of one indicates the cell is a surface water feature and/or in the hydrologically connected zone. Because the HCZ is based on a topographic moisture index rather than as a zone of assigned proximity to waters mapped at 1:100,000 scale, it can differ substantially from the Riparian zone; such as, when river floodplains far exceed the Riparian Zone’s standard 100 meters-per-side width, or when moist HCZ areas occur along small tributaries not mapped at 1:100,000 scale (see also Riparian Zone).

Map Name: Layers


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Layers: Description:

Copyright Text: US EPA, Region 4

Spatial Reference: PROJCS["NAD_1983_Albers",GEOGCS["GCS_North_American_1983",DATUM["D_North_American_1983",SPHEROID["GRS_1980",6378137.0,298.257222101]],PRIMEM["Greenwich",0.0],UNIT["Degree",0.0174532925199433]],PROJECTION["Albers"],PARAMETER["False_Easting",0.0],PARAMETER["False_Northing",0.0],PARAMETER["Central_Meridian",-96.0],PARAMETER["Standard_Parallel_1",29.5],PARAMETER["Standard_Parallel_2",45.5],PARAMETER["Latitude_Of_Origin",23.0],UNIT["Meter",1.0]]

Single Fused Map Cache: false

Initial Extent: Full Extent: Units: esriMeters


Document Info: Supports Dynamic Layers: false

MaxRecordCount: 1000

MaxImageHeight: 4096

MaxImageWidth: 4096

Supported Query Formats: JSON, AMF, geoJSON

Min Scale: 0

Max Scale: 0

Supports Datum Transformation: true

Child Resources:   Info

Supported Operations:   Export Map   Identify   QueryDomains   Find   Return Updates   Generate KML