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.
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.
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This data was downloaded from the NHD Data Viewer portal: http://viewer.nationalmap.gov/viewer/nhd.html?p=nhd.
- 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).
- 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.
- Symbols were created using the Description Field.
Each of the datasets below contain the following data:
- Download the raw dataset extracted from the USGS NHD site: lacounty_nhd_data_raw.zip (zipped personal geodatabase) – 10 MB
- Download the extracted dataset as created by LA County: lacounty_nhd_data_extracted.zip (zipped shapefiles, layer files, and .mxd file) – 18 MB
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.