NHDPlus High Resolution Data Download

This tool requires Network Analyst.

Summary

NHDPlus High Resolution Data Download downloads NHDPlus High Resolution (HR) hydrography data from the NHD Plus HR data server to your Liquids HCA project geodatabase and processes it to prepare it for use with the Hydro Trace tool.

To learn more about the Liquids HCA Tool in general, please see Liquids HCA Tool Frequently Asked Questions.

To learn more about the structure of the Liquids HCA Tool project geodatabase, please see Liquids HCA Tool Data Dictionary.

Usage

The National Hydrography Dataset (NHD) NHDPlus HR dataset stores a variety of feature types used by the Liquids HCA Tool in performing downstream transport analysis of hydrocarbon product plumes:

  • Watersheds – NHDPlus HR watersheds polygonal features that are recursive in nature, with smaller watershed units nested inside larger watershed units, each identified by a Hydrologic Unit Code (HUC) value. NHDPlus High Resolution Data Download downloads the highest resolution hydrography data available based on the boundaries of sub-regional watershed (HUC level 4) units.
  • Flowlines – NHD flowline features are polyline features that represent the flowing river/stream network in the NHDPlus HR dataset. They primarily comprise smaller rivers and streams that can be represented with simple polylines, as well as artificial linear paths delineating the flow network through larger rivers (and other hydrography features where flow is present) represented by NHD area polygons.
  • Areas – NHD areas primarily comprise the polygonal representations of larger (wider) rivers and other flowing bodies of water. Corresponding artificial flow paths in the NHD flowlines dataset define the flow network through the NHD area features.
  • Waterbodies – NHD waterbodies comprise the polygonal representations of nominally non-flowing waterbodies, such as lakes and ponds. For the sake of hydrographic network continuity, many of these nominally non-flowing waterbody features are accompanied by corresponding artificial flow paths in the NHD flowlines feature class that define the nominal flow network through these non-flowing waterbody features.

In addition to NHDPlus HR hydrography feature data, the Liquids HCA Tool also makes use of NHDPlus HR tabular data, including mean annual flow and monthly stream velocity estimates (1971 – 2000) for nearly all flowlines in the stream network. The Liquids HCA Tool performs a statistical analysis of the monthly average stream velocity data on a per flowline basis, which is then used to assign reasonable worst case (high) stream velocities to flowline features for use in downstream plume transport modeling. The assigned stream velocity for flowlines is the second positive deviation value of the monthly flowline stream velocities, or VEMA (NHD adjusted stream velocity), whichever is higher. For artificial path flowlines through small waterbodies (where water velocities are assumed to be low, but non-zero), the assigned stream velocity is the second negative deviation value of the monthly flowline stream velocities, or VEMA, whichever is lower. (In areas where NHDPlus HR flowline flow velocity data is missing, the Liquids HCA Tool uses velocities obtained from a statistical analysis of historic National Water Information System (NWIS) stream gauge data aggregated at the HUC-4 watershed level. This data is stored in the HydroHUC4SubRegionsVelocity table that is delivered with the Liquids HCA Tool software.

The NHDPlus HR dataset is optimized for use with Esri Geometric Network and Trace Network technology. While geometric and trace networks are useful for simple connectivity traces in a stream network, these technologies do not scale well for tracking downstream plume progress, particularly through highly anastomosing, interconnected stream networks wherein a multitude of potential flow paths are present.

For complex flow analyses of the sort performed by the Hydro Trace tool, Esri Network Analyst technology offers far more scalable performance. NHDPlus High Resolution Data Download constructs a Network Dataset from the downloaded NHDPlus HR data; the Hydro Trace tool treats the downstream trace computation as a Network Analyst service area analysis problem.

Following are the input parameters used by NHDPlus High Resolution Data Download:

  • Input Project Geodatabase – This is the Liquids HCA project file geodatabase you created with the Initialize Database By default, your input route features and sub-region watershed stream velocity table are sourced from your project file geodatabase, and the derived output NHDPlus HR feature classes are written to your project file geodatabase.
  • Input Route Features – This must be a valid route centerline feature class imported into your project geodatabase via the Initialize Database tool. By default, this parameter is populated with the ROUTES centerline routes feature class in your specified project geodatabase. If you specified a different name for your copied centerline route features when you ran Initialize Database, you’ll need to select that feature class here.
  • NHDPlus HR Data Source – This is the web data source for the NHDPlus HR hydrography data. The default value for this parameter is ‘USGS map service,’ which corresponds to the USGS NHD Plus HR data server.
  • NHDPlus HR Data Search Distance – This parameter is a distance value in the linear units of your choice that defines the search tolerance distance for NHDPlus HR HUC-4 level watersheds relative to your input route features. The highest resolution hydrography data available for any HUC-4 watershed within this distance of your input route features are selected for download into your project geodatabase. The default search distance value is 10 miles.
  • NHD Sub-Regional Watersheds Stream Velocity Table – This parameter is the HydroHUC4SubRegionsVelocity table from your project geodatabase (that is provided with the Liquids HCA Tool software and instantiated in your project file geodatabase by the Initialize Database tool). This table stores NWIS stream gauge stream velocity data aggregated at the HUC-4 watershed level. Generally, there should be no reason to alter this parameter value.

NHDPlus High Resolution Data Download imports the requested NHDPlus HR features into three feature classes located in the NWDataset feature dataset in your project geodatabase. These feature classes are exposed as feature layers in derived output parameters for the tool (along with the modified output project geodatabase). These derived output parameters do not appear in the tool interface, but are automatically exposed in ModelBuilder and are available for use in Python:

  • Output Project Geodatabase – This derived output parameter is the modified version of your input project geodatabase workspace, with the schema updated to reflect the addition of the new NWDataset feature dataset, together with its contained Network Dataset and imported NHDPlus HR feature classes.
  • Output NHD Flowline Features – This derived output parameter is a feature layer named ‘NHDFlowline,’ which is based on your imported NHDPlus HR flowline features. The NHDPlus HR flowline features are stored in your project geodatabase in the NHDFlowline m-aware polyline feature class in the NWDataset feature dataset.
  • Output NHD Area Features – This derived output parameter is a feature layer named ‘NHDArea,’ which is based on your imported NHDPlus HR area features. The NHDPlus HR area features are stored in your project geodatabase in the NHDArea polygon feature class in the NWDataset feature dataset.
  • Output NHD Waterbody Features – This derived output parameter is a feature layer named ‘NHDWaterbody,’ which is based on your imported NHDPlus HR waterbody features. The NHDPlus HR waterbody features are stored in your project geodatabase in the NHDWaterbody polygon feature class in the NWDataset feature dataset.
  • Output NHD HUC4 Boundary Features – This derived output parameter is a feature layer named ‘NHDHUC4Boundary,’ which is based on your imported NHDPlus HR HUC4 Boundary features. The NHDPlus HR HUC4 Boundary features are stored in your project geodatabase in the NHDHUC4Boundary polygon feature class in the NWDataset feature dataset.

NHDPlus High Resolution Data Download constructs a Network Dataset in your project geodatabase called ‘NHDFlowline_ND,’ located in the NWDataset feature dataset. As the name implies, this Network Dataset is based on the NHDFlowline feature class. The NHDFlowline_ND Network Dataset includes the obligatory NHDFlowline_ND_Junctions junctions feature class.

For more information on the NHDPlus HR dataset, see the USGS publication, User’s Guide for the National Hydrography Dataset Plus (NHDPlus) High Resolution.

In a typical Liquids HCA Tool workflow, NHDPlus High Resolution Data Download is run after Download Cases from Azure and before Calculate Land Spill NHD Intersections.

For visual reference on Liquids HCA Tool execution order, see Liquids HCA Tool Process Flow Diagrams.

Syntax

NHDDownload(in_workspace,in_route_features, in_huc_type, in_buffer_distance, in_huc4vel_tbl)

Parameter Explanation Data Type
in_workspace

Dialog Reference

Specify your input Liquids HCA project geodatabase.

There is no Python reference for this parameter.

Workspace
in_route_features

Dialog Reference

Specify your input centerline route features from your input project geodatabase.

There is no Python reference for this parameter.

Feature Layer
in_huc_type

Dialog Reference

Select your NHDPlus HR data provider.

There is no Python reference for this parameter.

String
in_buffer_distance

Dialog Reference

Specify the search tolerance distance for NHDPlus HR data relative to your input route features.

There is no Python reference for this parameter.

String
in_huc4vel_tbl (Optional)

Dialog Reference

Specify the table in your input project geodatabase that stores NWIS stream gauge stream velocity data aggregated at the HUC-4 watershed level.

There is no Python reference for this parameter.

Table

Derived Output

Name Explanation Data Type
out_gdb The schema-updated output version of your input project geodatabase. Workspace
out_flowline_fc A feature layer named ‘NHDFlowline’ based on the output NHDFlowline polyline feature class in the output NWDataset feature dataset in your project geodatabase. Feature Layer
out_areas_fc A feature layer named ‘NHDArea’ based on the output NHDArea polygon feature class in the output NWDataset feature dataset in your project geodatabase. Feature Layer
out_waterbody_fc A feature layer named ‘NHDWaterbody’ based on the output NHDWaterbody polygon feature class in the output NWDataset feature dataset in your project geodatabase. Feature Layer
out_boundary_fc A feature layer named ‘NHDHUC4Boundary’ based on the output NHDHUC4Boundary polygon feature class in the output NWDataset feature dataset in your project geodatabase. Feature Layer

Code sample

The following Python example script demonstrates how to use NHDPlus High Resolution Data Download in Python scripting, and illustrates how to download NHDPlus HR data for HUC-4 watersheds with a 10-mile radius of your input route features:

import arcpy
# Import Liquids HCA Tools
arcpy.ImportToolbox(r”C:\Program Files\ArcGIS\Pro\bin\Python\envs\arcgispro-py3\Lib\site-packages\liquidshca\esri\toolboxes\LiquidsHCA.pyt”)
#Parameters values assignment
In_workspace = r” C:\MyProject\SourceInputs.gdb “
route_features = r”C:\MyProject\SourceInputs.gdb\Routes”
subregion_velocity_records=r”C:\MyProject\SourceInputs.gdb\HydroHUC4SubRegionsVelocity”
arcpy.liquidshca.NHDDownload(in_workspace,route_features,”USGS map service”, “10 Miles”, subregion_velocity_records)

Environments

Current Workspace, Scratch Workspace, Default Output Z Value, M Resolution, M Tolerance, Output M Domain, Output XY Domain, Output Z Domain, Output Coordinate System, Geographic Transformations, Output has M values, Output has Z values, XY Resolution, XY Tolerance, Z Resolution, Z Tolerance

Licensing information

This tool requires a valid Liquids HCA Tool user license or subscription. Please see the Request License and Register License tool help topics for details on obtaining and registering a Liquids HCA Tool software license.

This tool requires a Network Analyst license.

Related Topics

Tags

Liquids HCA, NHD, NHDPlus HR, Hydro Trace.

Credits

Copyright © 2003-2020 by G2 Integrated Solutions, LLC. All Rights Reserved.

Use limitations

There are no access and use limitations for this item.