The Provisional Health District Layer contains Department of Public Health Health Districts as of 2011, which are aggregates of 2010 Census Tracts. Furthermore, Health Districts comprise the building blocks of Los Angeles County Service Planning Areas (SPAs). The Provisional Health Districts were created by the Los Angeles County Department of Public Health for planning purposes and are subject to change.

Parcel shapes from the 2017 Assessor Tax Roll

Funded by the Los Angeles County Board of Supervisors, the Arts Commission administers the sponsorship of free concerts at community venues throughout Los Angeles County to provide access to quality music programming representing the diversity of County residents.

The Fire Department’s jursidictional areas. Includes: Stations-170, Battalions-22, Divisions-9 and Regions-3. There are 198 individual polygons with 30 Stations having 2 or more discrete polygons.

Park planning areas are used to assist in calculating park fees for sub dividers in accordance with Los Angeles County Code, Title 21.

PRC 4201 - 4204 and Govt. Code 51175-89 direct the California Department of Forestry and Fire Protection (CAL FIRE) to map areas of significant fire hazards based on fuels, terrain, weather, and other relevant factors. These zones, referred to as Fire Hazard Severity Zones (FHSZ), define the application of various mitigation strategies to reduce risk associated with wildland fires. CAL FIRE is remapping Fire Hazard Severity Zones (FHSZ) for State Responsibility Areas (SRA) and Very High Fire Hazard Severity Zones (VHFHSZ) recommendations in Local Responsibility Areas (LRA) to provide updated map zones, based on new data, science, and technology. This specific dataset provides FHSZs within SRA lands only, and represents the proposed zones, subject to changes based on local hearings. A subsequent dataset release will provide the actual adopted zones. Maps of the proposed zones in SRA are available at: http://frap.cdf.ca.gov/projects/hazard/fhz.html More information about the project can be found at: http://frap.cdf.ca.gov/projects/hazard/hazard.html

The CT00 layer contains polygons for census areas. The source for the information in this layer is the U.S. Bureau of the Census and appropriate county government agencies.
This file is extracted from the Los Angeles County Registrar/Recorder's Precinct Information File, which is designed to match the Thomas Brothers TRNL (road network) layer.
Where census boundaries are defined by streets, water, city boundaries, or other features, those arc segments are copied to the CT00 layer, so that census tracts and other layer features match perfectly.

This dataset contains rivers, streams, and water conveyance mechanisms (pipelines, aqueducts).

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.