This tiled imagery service represents a snapshot of the land surface within Napa County and is made available for public use. The tile cache scheme follows the ArcGIS Online Model and can viewed down to ~1:283 scale. A hard copy of this data is also available directly from the GIS Team. For more information, contact gisstaff@countyofnapa.org.Extent and Resolution:Orthoimagery and Oblique imagery within Napa County, California. Projection:Capture Window:Bands:Sensor:Accuracy of Orthophotography:For questions regarding use and access, please contact gisstaff@countyofnapa.org.

CDFW BIOS GIS Dataset, Contact: VegCAMP Vegetation Classification and Mapping Program, Description: Napa County has used a 2004 edition vegetation map produced using the Manual of California Vegetation classification system (Thorne et al. 2004 ) as one of the input layers for land use decisions and policy. The county decided to update the map because of its utility. A University of California, Davis (UCD) group was engaged to produce the map. The new version was delivered to the county on 4, June 2019.

Link to the ScienceBase Item Summary page for the item described by this metadata record. Service Protocol: Link to the ScienceBase Item Summary page for the item described by this metadata record. Application Profile: Web Browser. Link Function: information

Link to the ScienceBase Item Summary page for the item described by this metadata record. Service Protocol: Link to the ScienceBase Item Summary page for the item described by this metadata record. Application Profile: Web Browser. Link Function: information

In 1995, the Manual of California Vegetation (MCV) introduced a quantitatively based method for classifying and mapping vegetation in California. In 2002 Department of Fish and Wildlife, Information Center for the Environment, and Aerial Information Systems used this method to develop a classification of vegetation types for Napa County, and to attribute the polygons of a new vegetation map. The complete report for this study can be viewed at: http://www.nrm.dfg.ca.gov/FileHandler.ashx?DocumentID=14660.

A map highlighting the drainage basins defined by Napa County in their modeling efforts. The Napa County Watersheds were generated from two elevation datasets. The Napa River Watershed was generated from LIDAR data processed by NCALM at UC Berkeley (https://calm.geo.berkeley.edu/ncalm/index.html). The eastern side of the county was delineated from DTM data which was generated from aerial photography (2002). The watersheds are intended to be used for hydrologic modeling and planning.Ridgelines are also from Napa County and depict major and minor ridgelines.Other topographic features important to wildfire planning may in added in the future.

Napa County has used a 2004 edition vegetation map produced using the Manual of California Vegetation classification system (Thorne et al. 2004) as one of the input layers for land use decision and policy. The county decided to update the map because of its utility. A University of California, Davis (UCD) group was engaged to produce the map. The earlier map used black and white digital orthophoto quadrangles from 1993, with a pixel resolution of 3 meters. This image was delineated using a heads up digitization technique produced by ASI (Aerial Services Incorporated). The resulting polygons were the provided vegetation and landcover attributes following the classification system used by California State Department of Fish and Wildlife mappers in the Manual of California Vegetation. That effort included a brief field campaign in which surveyors drove accessible roads and verified or corrected the dominant vegetation of polygons adjacent to roadways or visible using binoculars. There were no field relevé or rapid assessment plots conducted. This update version uses a 2016 edition of 1 meter color aerial imagery taken by the National Agriculture Imagery Program (NAIP) as the base imagery. In consultation with the county we decided to use similar methods to the previous mapping effort, in order to preserve the capacity to assess change in the county over time. This meant forgoing recent data and innovations in remote sensing such as the use LiDAR and Ecognition’s segmentation of imagery to delineate stands, which have been recently used in a concurrent project mapping of Sonoma County. The use of such technologies would have made it more difficult to track changes in landcover, because differences between publication dates would not be definitively attributable to either actual land cover change or to change in methodology. The overall cost of updating the map in the way was approximately 20% of the cost of the Sonoma vegetation mapping program. More information can be found at this site.

A map with various base layers to be used as a template for creating thematic maps for the Napa County CWPP online maps. Most layers are from Napa County's online gis data catalog but some layers were derived from public data sources such as Wikipedia and others.This map highlights WUI areas as defined by CAL FIRE in their WUI 12_3 layer. Description below:This dataset adds housing density class (DEN4) and wildfire hazard (FHSZ) attributes to WUI12_2 - FRAP’s preliminary result in an effort to capture Wildland Urban Interface (WUI) for the 2015 Assessment. The current dataset is appropriate for displaying the overall pattern of WUI development at the county level, and comparing counties in terms of development patterns. Until the dataset is refined through a field review process, it is not suited for WUI designations for individual houses or neighborhoods.

Three WUI classes are mapped: 1) Wildland Urban Interface – dense housing adjacent to vegetation that can burn in a wildfire, 2) Wildland Urban Intermix - housing development interspersed in an area dominated by wildland vegetation subject to wildfire, and 3) Wildfire Influence Zone - wildfire susceptible vegetation up to 1.5 miles from Wildland Urban Interface or Wildland Urban Intermix.

Housing Density (DEN4) 1) Less than one house per 20 acres 2) One house per 20 acres to one house per 5 acres 3) More than one house per 5 acres to 1 house per acre 4) More than 1 house per acre

Fire Hazard Severity Zone (HAZ_NUM: 1=Moderate, 2=High, 3=Very High) Source: State Resposibility Areas (fhszs06_3), Local Responsibility Areas (fhszl11_1)

This shapefile contains tax rate area (TRA) boundaries in Napa County for the specified assessment roll year. Boundary alignment is based on the 2019 county parcel map. A tax rate area (TRA) is a geographic area within the jurisdiction of a unique combination of cities, schools, and revenue districts that utilize the regular city or county assessment roll, per Government Code 54900. Each TRA is assigned a six-digit numeric identifier, referred to as a TRA number. TRA = tax rate area number

The California Department of Fish and Wildlife (Department) Vegetation Classification and Mapping Program (VegCAMP) created a fine-scale vegetation classification and map of the southern addition to the Departments Knoxville Wildlife Area (WA), Napa County, California following State Vegetation Survey, Federal Geographic Data Committee (FGDC), and National Vegetation Classification (NVC) Standards (Grossman et al 1998). The vegetation classification was derived from data collected in the field following the Combined Rapid Assessment and Relevé Protocol during the periods November 18''20, 2013 and April 28''May 1, 2014. Vegetation polygons were drawn using heads-up manual digitizing using the 2011 Napa County 30-cm resolution color infrared (CIR) imagery as the base imagery. Supplemental imagery included National Agricultural Imagery Program (NAIP) true color and CIR 1-meter resolution data from 2009''2012, BING imagery, and current and historical imagery from Google Earth. The minimum mapping unit (MMU) is 1 acre, with the exception of wetland types, which have an MMU of 1/2 acre. Ponds, riparian types, and the one vernal pool on the WA that were visible on the imagery were mapped regardless of size, and streams were generally mapped if greater than 10 m wide (narrower portions may have been mapped to maintain the continuity of the streams). Mapping is to the NVC hierarchy association, alliance, or group level based on the ability of the photointerpreters to distinguish types based on all imagery available and on the field data. Both the existing (northern) and new addition (southern) portions of the Knoxville WA were mapped in 2002 as part of the Napa County vegetation map (https://nrm.dfg.ca.gov/FileHandler.ashx?DocumentID=14660). The 2002 map is at a coarse thematic resolution (alliance through macrogroup level) and vegetation in portions of the WA has changed since the 2004 Rumsey Fire, necessitating this map update. We have produced an updated version of the KWA portion of the 2002 map layer that uses the same spatial data, but added a crosswalk to the current classification and the upper levels of the current hierarchy. This map layer is included in the downloaded dataset for this map and an expanded metadata report for that crosswalk can be found at https://nrm.dfg.ca.gov/FileHandler.ashx?DocumentID=164825.

Countywide vegetation classes based on definitions found in the Napa County Water Quality & Tree Protection Ordinance (WQTPO).More information related to the WQTPO and these classes can be found in the following documents:Final Ordinance, approved 4/9/2019 Implementation Guide to the WQTPOThis layer is a view of the original Vegetation layer. The description from the source layer follows:Napa County has used a 2004 edition vegetation map produced using the Manual of California Vegetation classification system (Thorne et al. 2004) as one of the input layers for land use decision and policy. The county decided to update the map because of its utility. A University of California, Davis (UCD) group was engaged to produce the map.The earlier map used black and white digital orthophoto quadrangles from 1993, with a pixel resolution of 3 meters. This image was delineated using a heads up digitization technique produced by ASI (Aerial Services Incorporated). The resulting polygons were the provided vegetation and landcover attributes following the classification system used by California State Department of Fish and Wildlife mappers in the Manual of California Vegetation. That effort included a brief field campaign in which surveyors drove accessible roads and verified or corrected the dominant vegetation of polygons adjacent to roadways or visible using binoculars. There were no field relevé or rapid assessment plots conducted.This update version uses a 2016 edition of 1 meter color aerial imagery taken by the National Agriculture Imagery Program (NAIP) as the base imagery. In consultation with the county we decided to use similar methods to the previous mapping effort, in order to preserve the capacity to assess change in the county over time. This meant forgoing recent data and innovations in remote sensing such as the use LiDAR and Ecognition’s segmentation of imagery to delineate stands, which have been recently used in a concurrent project mapping of Sonoma County. The use of such technologies would have made it more difficult to track changes in landcover, because differences between publication dates would not be definitively attributable to either actual land cover change or to change in methodology. The overall cost of updating the map in the way was approximately 20% of the cost of the Sonoma vegetation mapping program.Therefore, we started with the original map, and on-screen inspections of the 2004 polygons to determine if change had occurred. If so, the boundaries and attributes were modified in this new edition of the map. We also used the time series of imagery available on Google Earth, to further inspect many edited polygons. While funding was not available to do field assessments, we incorporated field expertise and other map data from four projects that overlap with parts of Napa Count: the Angwin Experimental Forest; a 2014 vegetation map of the Knoxville area; agricultural rock piles were identified by Amber Manfree; and parts of a Sonoma Vegetation Map that used 2013 imagery.The Angwin Experimental Forest was mapped by Peter Lecourt from Pacific Union College. He identified several polygons of redwoods in what are potentially the eastern-most extent of that species. We reviewed those polygons with him and incorporated some of the data from his area into this map.The 2014 Knoxville Vegetation map was developed by California Department of Fish and Wildlife. It was made public in February of 2019, close to the end of this project. We reviewed the map, which covers part of the northeast portion of Napa County. We incorporated polygons and vegetation types for 18 vegetation types including the rare ones, we reviewed and incorporated some data for another 6 types, and we noted in comments the presence of another 5 types. There is a separate report specifically addressing the incorporation of this map to our map.Dr Amber Manfree has been conducting research on fire return intervals for parts of Napa County. In her research she identified that large piles of rocks are created when vineyards are put in. These are mapable features. She shared the locations of rock piles she identified, which we incorporated into the map.The Sonoma Vegetation Map mapped some distance into the western side of Napa County. We reviewed that map’s polygons for coast redwood. We then examined our imagery and the Google imagery to see if we could discern the whorled pattern of tree branches. Where we could, we amended or expanded redwood polygons in our map.The Vegetation classification systems used here follows California’s Manual of California Vegetation and the National Vegetation Classification System (MCV and NVCS). We started with the vegetation types listed in the 2004 map. We predominantly use the same set of species names, with modifications/additions particularly from the Knoxville map. The NVCS uses Alliance and Association as the two most taxonomically detailed levels. This map uses those levels. It also refers to vegetation types that have not been sampled in the field and that has 3-6 species and a site descriptor as Groups, which is the next more general level in the NVCS classification.We conducted 3 rounds of quality assessment/quality control exercises.

Internal view of the parcel layer. This view contains all the attributes that can be seen by County employees.There are approximately 51,300 real property parcels in Napa County. Parcels delineate the approximate boundaries of property ownership as described in Napa County deeds, filed maps, and other source documents. GIS parcel boundaries are maintained by the Information Technology Services GIS team. Assessor Parcel Maps are created and maintained by the Assessor Division Mapping Section. Each parcel has an Assessor Parcel Number (APN) that is its unique identifier. The APN is the link to various Napa County databases containing information such as owner name, situs address, property value, land use, zoning, flood data, and other related information. Data for this map service is sourced from the Napa County Parcels dataset which is updated nightly with any recent changes made by the mapping team. There may at times be a delay between when a document is recorded and when the new parcel boundary configuration and corresponding information is available in the online GIS parcel viewer.From 1850 to early 1900s assessor staff wrote the name of the property owner and the property value on map pages. They began using larger maps, called “tank maps” because of the large steel cabinet they were kept in, organized by school district (before unification) on which names and values were written. In the 1920s, the assessor kept large books of maps by road district on which names were written. In the 1950s, most county assessors contracted with the State Board of Equalization for board staff to draw standardized 11x17 inch maps following the provisions of Assessor Handbook 215. Maps were originally drawn on linen. By the 1980’s Assessor maps were being drawn on mylar rather than linen. In the early 1990s Napa County transitioned from drawing on mylar to creating maps in AutoCAD. When GIS arrived in Napa County in the mid-1990s, the AutoCAD images were copied over into the GIS parcel layer. Sidwell, an independent consultant, was then contracted by the Assessor’s Office to convert these APN files into the current seamless ArcGIS parcel fabric for the entire County. Beginning with the 2024-2025 assessment roll, the maps are being drawn directly in the parcel fabric layer.Parcels in the GIS parcel fabric are drawn according to the legal description using coordinate geometry (COGO) drawing tools and various reference data such as Public Lands Survey section boundaries and road centerlines. The legal descriptions are not defined by the GIS parcel fabric. Any changes made in the GIS parcel fabric via official records, filed maps, and other source documents are uploaded overnight. There is always at least a 6-month delay between when a document is recorded and when the new parcel configuration and corresponding information is available in the online parcel viewer for search or download.Parcel boundary accuracy can vary significantly, with errors ranging from a few feet to several hundred feet. These distortions are caused by several factors such as: the map projection - the error derived when a spherical coordinate system model is projected into a planar coordinate system using the local projected coordinate system; and the ground to grid conversion - the distortion between ground survey measurements and the virtual grid measurements. The aim of the parcel fabric is to construct a visual interpretation that is adequate for basic geographic understanding. This digital data is intended for illustration and demonstration purposes only and is not considered a legal resource, nor legally authoritative.SFAP & CFAP DISCLAIMER: Per the California Code, RTC 606. some legal parcels may have been combined for assessment purposes (CFAP) or separated for assessment purposes (SFAP) into multiple parcels for a variety of tax assessment reasons. SFAP and CFAP parcels are assigned their own APN number and primarily result from a parcel being split by a tax rate area boundary, due to a recorded land use lease, or by request of the property owner. Assessor parcel (APN) maps reflect when parcels have been separated or combined for assessment purposes, and are one legal entity. The goal of the GIS parcel fabric data is to distinguish the SFAP and CFAP parcel configurations from the legal configurations, to convey the legal parcel configurations. This workflow is in progress. Please be advised that while we endeavor to restore SFAP and CFAP parcels back to their legal configurations in the primary parcel fabric layer, SFAP and CFAP parcels may be distributed throughout the dataset. Parcels that have been restored to their legal configurations, do not reflect the SFAP or CFAP parcel configurations that correspond to the current property tax delineations. We intend for parcel reports and parcel data to capture when a parcel has been separated or combined for assessment purposes, however in some cases, information may not be available in GIS for the SFAP/CFAP status of a parcel configuration shown. For help or questions regarding a parcel’s SFAP/CFAP status, or property survey data, please visit Napa County’s Surveying Services or Property Mapping Information. For more information you can visit our website: When a Parcel is Not a Parcel | Napa County, CA

Boundary of the County of Napa developed using the California Government Code 23128 descriptions.

This map application is intended to show information related to fires and evacuations within Napa County.Data updates are performed regularly at the direction of the Napa County EOC's Incident Command, Operations and the Public Information Officer. Map source for application https://napacounty.maps.arcgis.com/home/item.html?id=cdec2f2115ef42e7874606f39d72ea12

Napa County Groundwater Sustainability Agency (GSA) boundary, established by Resolution 2019-152 on Dec. 17, 2019. The extent of this boundary is delineated by the CA Dept. of Water Resources ("Water Board") Bulletin 118 Groundwater Basins GIS layer, the specific GSA boundary in Napa County being Subbasin #2-002.01 "NAPA-SONOMA VALLEY - NAPA VALLEY".Specific information regarding this GSA can be found on the following Water Board page: https://sgma.water.ca.gov/portal/gsa/print/488

Parcels delineate the approximate boundaries of property ownership as described in Napa County deeds, filed maps, and other source documents. Parcel boundaries in GIS are created and maintained by the Assessor’s Division Mapping section and Information Technology Services. There are approximately 51,300 real property parcels in Napa County. Parcels delineate the approximate boundaries of property ownership as described in Napa County deeds, filed maps, and other source documents. GIS parcel boundaries are maintained by the Information Technology Services GIS team. Assessor Parcel Maps are created and maintained by the Assessor Division Mapping Section. Each parcel has an Assessor Parcel Number (APN) that is its unique identifier. The APN is the link to various Napa County databases containing information such as owner name, situs address, property value, land use, zoning, flood data, and other related information. Data for this map service is sourced from the Napa County Parcels dataset which is updated nightly with any recent changes made by the mapping team. There may at times be a delay between when a document is recorded and when the new parcel boundary configuration and corresponding information is available in the online GIS parcel viewer.From 1850 to early 1900s assessor staff wrote the name of the property owner and the property value on map pages. They began using larger maps, called “tank maps” because of the large steel cabinet they were kept in, organized by school district (before unification) on which names and values were written. In the 1920s, the assessor kept large books of maps by road district on which names were written. In the 1950s, most county assessors contracted with the State Board of Equalization for board staff to draw standardized 11x17 inch maps following the provisions of Assessor Handbook 215. Maps were originally drawn on linen. By the 1980’s Assessor maps were being drawn on mylar rather than linen. In the early 1990s Napa County transitioned from drawing on mylar to creating maps in AutoCAD. When GIS arrived in Napa County in the mid-1990s, the AutoCAD images were copied over into the GIS parcel layer. Sidwell, an independent consultant, was then contracted by the Assessor’s Office to convert these APN files into the current seamless ArcGIS parcel fabric for the entire County. Beginning with the 2024-2025 assessment roll, the maps are being drawn directly in the parcel fabric layer.Parcels in the GIS parcel fabric are drawn according to the legal description using coordinate geometry (COGO) drawing tools and various reference data such as Public Lands Survey section boundaries and road centerlines. The legal descriptions are not defined by the GIS parcel fabric. Any changes made in the GIS parcel fabric via official records, filed maps, and other source documents are uploaded overnight. There is always at least a 6-month delay between when a document is recorded and when the new parcel configuration and corresponding information is available in the online parcel viewer for search or download.Parcel boundary accuracy can vary significantly, with errors ranging from a few feet to several hundred feet. These distortions are caused by several factors such as: the map projection - the error derived when a spherical coordinate system model is projected into a planar coordinate system using the local projected coordinate system; and the ground to grid conversion - the distortion between ground survey measurements and the virtual grid measurements. The aim of the parcel fabric is to construct a visual interpretation that is adequate for basic geographic understanding. This digital data is intended for illustration and demonstration purposes only and is not considered a legal resource, nor legally authoritative.SFAP & CFAP DISCLAIMER: Per the California Code, RTC 606. some legal parcels may have been combined for assessment purposes (CFAP) or separated for assessment purposes (SFAP) into multiple parcels for a variety of tax assessment reasons. SFAP and CFAP parcels are assigned their own APN number and primarily result from a parcel being split by a tax rate area boundary, due to a recorded land use lease, or by request of the property owner. Assessor parcel (APN) maps reflect when parcels have been separated or combined for assessment purposes, and are one legal entity. The goal of the GIS parcel fabric data is to distinguish the SFAP and CFAP parcel configurations from the legal configurations, to convey the legal parcel configurations. This workflow is in progress. Please be advised that while we endeavor to restore SFAP and CFAP parcels back to their legal configurations in the primary parcel fabric layer, SFAP and CFAP parcels may be distributed throughout the dataset. Parcels that have been restored to their legal configurations, do not reflect the SFAP or CFAP parcel configurations that correspond to the current property tax delineations. We intend for parcel reports and parcel data to capture when a parcel has been separated or combined for assessment purposes, however in some cases, information may not be available in GIS for the SFAP/CFAP status of a parcel configuration shown. For help or questions regarding a parcel’s SFAP/CFAP status, or property survey data, please visit Napa County’s Surveying Services or Property Mapping Information. For more information you can visit our website: When a Parcel is Not a Parcel | Napa County, CA

Data last synced 08-29-2025 04:24. Data synced on a Weekly interval.

The Napa County Watersheds were generated from two elevation datasets. The Napa River Watershed was generated from LIDAR data processed by NCALM at UC Berkeley (http://calm.geo.berkeley.edu/ncalm/index.html). The eastern side of the county was delineated from DTM data which was generated from aerial photography (2002). The watersheds are intended to be used for hydrologic modeling and planning.

Data last synced 09-01-2025 06:05. Data synced on a Monthly interval.

For 21 vegetation types (PIs), random polygons of each of the 5 density classes were selected to estimate tree crown density in each polygon. The polygons in each unique PI and Density class combination were then averaged and those averages are recorded in this table. Tree crown density was estimated for PIs with oak as a dominant tree type, as well as some PIs not dominated by oaks. For each PI, 5 polygons were selected per density class; or for PIs which did not have at least 5 polygons per density class, all polygons in the density class were used. In each polygon, we counted the number of tree crowns, or if the polygon was very large, we counted crowns in a small sample of the polygon and used the sample to estimate tree crowns in the entire polygon. Note that because it is sometimes difficult to distinguish between oaks and other trees, we estimated total tree crowns—not necessarily just oak crowns. Once the number of tree crowns in each polygon was estimated, we divided the number of trees by polygon area to obtain an estimate of tree density (in trees/acre). Tree density was estimated for the following PIs:• 1000 series (1101, 1122, 1123, 1124, 1126, 1201, 1202, 1221, 1222, 1223)• 2000 series (2104, 2121, 2123, 2126, 2222, 2230)• 3000 series (3101, 3102, 3121, 3122, 3123, 3124, 3125)

The purpose of this layer is for reconnaissance level planning and regional assessment of historical tidal wetlands of the San Francisco Bay Area.Layer geometry was updated in 2025 as part of a county-wide data refresh. Updated geometry was taken from SFEI “Historical Habitats” gis data, filtering for “marsh” “tidal” and “channel”. SFEI used the 1971 map* the original hist_marsh_mrgn layer was made to represent and refined its boundaries with additional historical habitat data.More information can be found at: https://www.sfei.org/projects/napa-valley-historical-ecology-atlas