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Layer: NYC Watershed (ID:4)

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Name: NYC Watershed

Display Field: REGION

Type: Feature Layer

Geometry Type: esriGeometryPolygon

Description: Official NYC East-of-Hudson and West-of-Hudson outer watershed boundaries delineated from 2009 LiDAR-derived 1-meter Digital Elevation Model (DEM). The 1m DEM was derived from airborne LiDAR data collected in 2009 as part of the NYS Digital Ortho Program under contract with NYCDEP under CAT-371. For individual reservoir drainage basin boundaries, see the "NYCbasin1m" feature class.As part of the NYC Watershed 2009 LiDAR National Hydrography Dataset (NHD) Update Project: Reservoir and Watershed Boundary Dataset 8-digit Hydrologic Unit (8-d HU) boundaries were created by IAGT/RACNE under CAT-393 for each of the West of Hudson (WOH) Reservoirs in the Catskills Mountains. In the EOH Taconic Mountains, there is a single 8-digit HUC boundary for all of the 17 reservoirs draining into the Lower Hudson sub-watershed through the New Croton Reservoir spillway, plus another for the Kensico Reservoir. These basins were dissolved together by DEP staff to create this layer representing only the outer NYC watershed boundary.Polygons representing differences between this 1m product and older 1:24K-derived basins were created and manually reviewed for correctness by NYSDEP BWS GIS and ERA Wetlands staff using high resolution aerial imagery, 2 ft contours, 1m DEM hillshade, GPS-ed culvert locations, GoogleMaps drive-by imagery, and BING Birds-eye imagery. In cases where office techniques could not easily determine correctness, field visits using sub-meter GPS data collection were performed by ERA Wetlands and GIS staff to make final determination. 1m Basin data were edited as needed by BWS GIS staff based on manual review. FALL 2020 NOTE: In Fall 2020, two changes were made to the official NYC watershed and basin boundaries as follows: 1) The Diverting Reservoir boundary in EOH was updated, which in-turn required a change in the basin and subbasin boundary there. 2) Based on the results of a watershed boundary field inspection by REP and GIS Staff, as per the watershed delineation SOP, a very small portion of the outer Cannonsville Reservoir boundary in WOH, T. Delhi required updating, which in-turn required a change in the basin and subbasin boundary there.These changes have been reflected in this basin-derived dataset.Because original vector data contained jagged edges as a by-products of the original raster gridded elevation data, a 10m x 10m smoothing filter was run on the exterior NYC watershed boundary and interior WOH basin boundaries, while a 5m x 5m smoothing filter was run on the smaller interior EOH basins. Each smoothed line was checked to ensure any elevation summits and ridgelines were still captured and that the line was true to the original catch basin delineation. In addition, DEP staff applied a simplification process to the boundaries. Because of the slowness in speed and performance due to the amount of vertices, the simplify line tool was used to reduce the amount of vertices, resulting in an increase in drawing and processing speeds. Again, staff checked the result to ensure that accuracy was not compromised. Sections of basin edges were also snapped to reservoir spillway edges and top-of-dam lines in the "NHDLine" and Auxiliary "breakline" feature classes where appropriate. This work was performed on the subbasin product first, and then all other basin related products were created. These were the steps used:Convert NYCsubbasin1m to arcsRun “simplify line” tool (Bend Simplify, 5m) on arcsConvert arcs result to polygonsRun repair geometryCreate basin1m (and related product) from subbasins1mIAGT/RACNE methodology: A single vector line feature class was directly derived from the 1m DEM, then manually reviewed. Polygonal feature classes were then derived from the line feature class, with a topology requirement to achieve polygonal closure and no non-hydrologic polygons. Lines were produced by TauDEM flow analysis of Reference DEM (1 m, version 0). Segment review was performed using 0.5 m interval contours and 2012 Hydrographic and Topographic Breaklines as guidelines. Vector process boundaries are the raster boundaries above plus those corresponding to areas downstream of the reservoirs that drain the corresponding WBD 8-d HU. See "2D Breakline Features and Hydrography Compilation Standard and Protocol" for details on the hydrography used in the review.

Copyright Text: Original data (NYC outer-watershed boundary and 8-digit HUC basins) developed under NYCDEP contract CAT-393 by RACNE. QA edits developed in-house by NYCDEP BWS GIS. This data packaging is owned by the New York City Department of Environmental Protection, Bureau of Water Supply, 2013.

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Max Record Count: 2000

Supported query Formats: JSON, geoJSON, PBF

Use Standardized Queries: True

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Has Geometry Properties: true

HTML Popup Type: esriServerHTMLPopupTypeAsHTMLText

Object ID Field: OBJECTID

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Is Data Versioned: false

Has Contingent Values: false

Supports Rollback On Failure Parameter: true

Last Edit Date: 10/7/2024 6:23:45 PM

Schema Last Edit Date: 2/6/2024 6:12:06 PM

Data Last Edit Date: 1/22/2024 4:58:05 PM

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