Log In

Watershed Boundaries

This dataset contains watershed boundaries for watersheds covering Los Angeles County.

This dataset was downloaded, extracted and prepared from the National Hydrography Dataset.  The NHD is a comprehensive effort by the US Geological Survey to manage and maintain a comprehensive, high quality, nationwide dataset for GIS mapping and analysis of water features and conveyance.  While it is not perfect, and you may find a number of errors, LA County applauds this effort, and is determined to support the enhancement and maintenance of this valuable information since it supports our long-term goal of public, authoritative data.  We are currently investigating the feasibility of stewarding the NHD data for the LA County region.

A description of the NHD from the USGS site:

The National Hydrography Dataset (NHD) is the surface water component of The National Map. The NHD is a digital vector dataset used by geographic information systems (GIS). It contains features such as lakes, ponds, streams, rivers, canals, dams and streamgages. These data are designed to be used in general mapping and in the analysis of surface-water systems.

Samples

Please note that the symbology on the attached maps (and the layers within the downloads) are those developed by the County in order to highlight various hydrographic features.  They are not final in any way.  These sample images contain symbology for all of the NHD layers, since we are making the data available as a single download.

Click a thumbnail to expand

Legend

Countywide

Mid-zoom

Zoomed

Watersheds

Watershed(2)

Processing steps

This data was downloaded from the NHD Data Viewer portal: http://viewer.nationalmap.gov/viewer/nhd.html?p=nhd.

  1. I selected the data covering the County of Los Angeles and retrieved the data in personal geodatabase format (I have link to download that file below).
  2. To prepare the shapefiles that are available for download, I have joined the features to their descriptions in the NHDFCODE table through the FCODE field and exported them, since a direct export from the geodatabase will not include the related information.  To ensure consistency, I have not deleted any fields that have been created through this join.
  3. Symbols were created using the Description Field.

Data Downloads

Each of the datasets below contain the following data:

The extracted file includes the following shapefiles:

  • Hydro Points – nhd_points_withcodes.shp
  • Hydro Lines – nhd_flowline_withcodes.shp
  • Hydro Polygons – nhd_waterbody_withcodes.shp
  • Watershed Boundaries (Levels 8,10, & 12)

It also includes a number of ArcMap 10 layer files that reference the data, and an ArcMap 10 .mxd file as well.


GIS Data Disclaimer

Data Field Descriptions

Detailed information can be obtained from the NHD Data Dictionary, accessible here: http://nhd.usgs.gov/NHDDataDictionary_model2.0.pdf.  This will correspond directly to the raw data download.

For cartographic purposes, here are the most important fields:

  • GNIS_Name: Name of the feature
  • Descriptio: Feature Type (used for symbolization) - this was joined from the NHDFCODE table.

 


GIS Source Information
Database Name: EGIS_HYDRO
Feature Class Name: NHD_HUC8
Feature Dataset Name (if applicable):
Reference Date: 2011
Accuracy: TIGER
Update Frequency: Unknown
Access Constraints:None

Contact Information
Drew Decker
USGS Geospatial Liaison for California
US Geological Survey
NSDI Partnership Office
4165 Spruance Road
Suite 200
San Diego, CA 92101
ddecker@usgs.gov
(619) 225-6430
Add Comment Register



Leave a Reply