NOAA Office for Coastal Management Coastal Inundation Digital Elevation Model: Portland (OR) WFO - Clatsop, Columbia, and Multnomah Counties

This digital elevation model (DEM) is a part of a series of DEMs produced for the National Oceanic and Atmospheric Administration Office for Coastal Management's Sea Level Rise and Coastal Flooding Impacts Viewer. The DEMs created for this project were developed using the NOAA National Weather Service's Weather Forecast Office (WFO) boundaries. Because the WFO boundaries can cover large areas, the WFO DEM was divided into smaller DEMs to ensure more manageable file sizes. The Portland (OR) WFO DEM was split into two smaller DEMs. They are divided along county lines and are: 1. Portland (OR) WFO - Tillamook, Lincoln, and Lane Counties 2. Portland (OR) WFO - Clatsop, Columbia, and Multnomah Counties This metadata record describes the DEM for the Portland (OR) WFO - Clatsop, Columbia, and Multnomah Counties. The DEM includes the best available lidar data known to exist at the time of DEM creation for the coastal areas of Clatsop, Columbia, and Multnomah counties, that met project specifications. Please note that the Portland WFO boundary extends into Washington state. The Washington portion of the WFO is also available for download from NOAA OCM as a separate product. The DEM is derived from LiDAR datasets collected for the Oregon Department of Geology and Mineral Industries (DoGAMI) and the U.S. Army Corps of Engineers (USACE). LiDAR data for a portion of Clatsop County, was collected for DoGAMI in 2008-2009. LiDAR data along the Columbia River in Clatsop, Columbia and Multnomah counties was collected for USACE in 2010. Hydrographic breaklines used in the creation of the DEM were delineated using LiDAR intensity imagery generated from the DoGAMI datasets and were also obtained from USACE. The DEMs are hydro flattened such that water elevations are less than or equal to 0 meters. The DEM is referenced vertically to the North American Vertical Datum of 1988 (NAVD88) with vertical units of meters and horizontally to the North American Datum of 1983 (NAD83). The resolution of the DEM is approximately 5 meters.

The NOAA Office for Coastal Management has developed high-resolution digital elevation models (DEMs) for use in the Center's Sea Level Rise And Coastal Flooding Impacts internet mapping application. These DEMs serve as source datasets used to derive data to visualize the impacts of inundation resulting from sea level rise along the coastal United States and its territories.

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All datasets used to construct this DEM are publicly available via the NOAA Office for Coastal Management's Digital Coast (www.coast.noaa.gov/lidar). Further information regarding the constituent lidar datasets of this DEM can be accessed using the following url's: https://coast.noaa.gov/dataviewer/webfiles/metadata/or2009_dogami_north_coast_template.html https://coast.noaa.gov/dataviewer/webfiles/metadata/or2010_usace_columbia_river_template.html

Spatial_Reference_Information:

Horizontal_Coordinate_System_Definition:

Geographic:

Latitude_Resolution: 0.0000001

Longitude_Resolution: 0.0000001

Geographic_Coordinate_Units: Decimal degrees

Geodetic_Model:

Horizontal_Datum_Name: North American Datum of 1983

Ellipsoid_Name: Geodetic Reference System 80

Semi-major_Axis: 6378137.000000

Denominator_of_Flattening_Ratio: 298.257222101

Vertical_Coordinate_System_Definition:

Altitude_System_Definition:

Altitude_Datum_Name: North American Vertical Datum of 1988

Altitude_Resolution: 0.001

Altitude_Distance_Units: meters

Altitude_Encoding_Method: Explicit elevation coordinate included with horizontal coordinates

Any conclusions drawn from the analysis of this information are not the responsibility of the Office for Coastal Management or its partners.

None

The dataset is provided "as is," without warranty to its performance, merchantable state, or fitness for any particular purpose. The entire risk associated with the results and performance of this dataset is assumed by the user. This dataset should be used strictly as a planning reference and not for navigation, permitting, or other legal purposes.

The DEM is derived from the source lidar data. Horizontal accuracy testing is not performed on the DEM. Lidar source data assumed to meet 1 meter horizontal accuracy.

The DEM is derived from the source lidar data. Vertical accuracy is not tested on the DEM. Project specifications require all source lidar data used in constructing the DEM to meet FEMA Specifications for Flood Hazard Mapping.

A visual qualitative check was performed to ensure data completeness. All available lidar data known at the time of DEM creation that meets project specifications has been used to develop the DEM. Known data gaps may exist where lidar coverage was incomplete.

Data covers the project area, defined as the WFO boundary. Elevation data checked for anomalous elevation values outside expected range.