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This dataset comprises National Hydrology Dataset (NHD) flowline data for the two HU6 (hydrographic units level 6) that intersect San Diego County (i.e. Laguna-San Diego Coastal and Salton Sea units).
NHD data was downloaded in FGDB format for HU-4 (SubRegion) for NHD_H_1810_HU4 and NHD_H1807_HU4 from https://apps.nationalmap.gov/downloader/ Features from NHDFlowline feature class from NHD_H_1810_HU4 and NHD_H1807_HU4 were selected that intersect the two HU6 units and were projected to NAD83 State Plane Coordinate System.
NHDFlowlines consist of routes that make up a linear surface water drainage network. Flowlines have a reach code and a measure, allowing for the establishment of upstream/downstream relationships. This network allows for powerful analysis and modeling capabilities.
The National Hydrography Dataset (NHD) is a feature-based database that interconnects and uniquely identifies the stream segments or reaches that make up the nation's surface water drainage system. NHD data was originally developed at 1:100,000-scale and exists at that scale for the whole country. This high-resolution NHD, generally developed at 1:24,000/1:12,000 scale, adds detail to the original 1:100,000-scale NHD. (Data for Alaska, Puerto Rico and the Virgin Islands was developed at high-resolution, not 1:100,000 scale.) Local resolution NHD is being developed where partners and data exist. The NHD contains reach codes for networked features, flow direction, names, and centerline representations for areal water bodies. Reaches are also defined on waterbodies and the approximate shorelines of the Great Lakes, the Atlantic and Pacific Oceans and the Gulf of Mexico. The NHD also incorporates the National Spatial Data Infrastructure framework criteria established by the Federal Geographic Data Committee.
Statements of horizontal positional accuracy are based on accuracy statements made for U.S. Geological Survey topographic quadrangle maps. These maps were compiled to meet National Map Accuracy Standards. For horizontal accuracy, this standard is met if at least 90 percent of points tested are within 0.02 inch (at map scale) of the true position. Additional offsets to positions may have been introduced where feature density is high to improve the legibility of map symbols. In addition, the digitizing of maps is estimated to contain a horizontal positional error of less than or equal to 0.003 inch standard error (at map scale) in the two component directions relative to the source maps. Visual comparison between the map graphic (including digital scans of the graphic) and plots or digital displays of points, lines, and areas, is used as control to assess the positional accuracy of digital data. Digital map elements along the adjoining edges of data sets are aligned if they are within a 0.02 inch tolerance (at map scale). Features with like dimensionality (for example, features that all are delineated with lines), with or without like characteristics, that are within the tolerance are aligned by moving the features equally to a common point. Features outside the tolerance are not moved; instead, a feature of type connector is added to join the features. This statement is generally true for the most common sources of NHD data. Other sources and methods may have been used to create or update NHD data. In some cases, additional information may be found in the NHDMetadata table.
This dataset was developed by SanGIS to depict major watercourses within San Diego County and does not include smaller feeder streams and ditches. The dataset was created from NHD Flowline data for streams with GNIS Names assigned. This dataset was projected and these data were then further edited to match San Diego County conditions. Additional streams were added and other streams removed based on input from SANDAG, County of San Diego and City of San Diego. Flowlines were extended through lakes and to the coastline using aerial imagery as a guide. This layer is for cartographic purposes only and should not be used for flow or other analyses.
This dataset is a combination of six elements of environmentally sensitive areas. Those elements are:
County of San Diego South County Multiple Species Conservation Program (MSCP) Hardline Preserve designation, (MSCP MAY 2022 DATA) SDEP.SANGIS.ECO_MSCP_CN
Preserved land within MSCP, (HABITRAK GAINS 2021)
MSCP Pre-Approved Mitigation Area (PAMA) designation, (MSCP MAY 2022 DATA) SDEP.SANGIS.ECO_MSCP_CN
Clean Water Act section 303(d) water bodies listed by the California Water Resources Control Board in 2018 with a 200 foot buffer, (SDEP.SANGIS.HYD_303D_200FT_CN)
Waters that support habitats necessary for the survival and successful maintenance of plant or animal species established under state and/or federal law as rare, threatened, or endangered from 2018. Table with Rarewaters Id’s downloaded from the California Water Resources Control Board.
Areas of Significant Biological Concern (ASBC). 2013 data, no new data is available in 2022.