2017 USGS Lidar DEM: Chenier Plain, LA

Product: These are Digital Elevation Model (DEM) data for LA Chenier Plain Lidar 2017 B16 Project Level as part of the required deliverables for LA Chenier Plain Lidar 2017 B16 project. Class 2 (ground) lidar points in conjunction with the hydro breaklines and bridge breaklines were used to create a 1 meter hydro-flattened Raster DEM.

Geographic Extent: AOI was located along an area of coastal Louisiana referred to as Chenier Plain, which includes portions of Calcasieu, Cameron, Vermillion, Iberia, and St. Mary Parishes. The area of interest covered approximately 2942 square miles. Dataset Description: LA Chenier Plain Lidar 2017 B16 project called for the planning, acquisition, processing and derivative products of lidar data to be collected at a nominal pulse spacing (NPS) of 0.70 meter. Project specifications are based on the U.S. Geological Survey National Geospatial Program Lidar Base Specification, Version 1.2. The data was developed based on a horizontal projection/datum of NAD83 (2011), UTM Zone 15N, Meter and vertical datum of NAVD88 (GEOID12B), Meter. Lidar data was delivered as: flightline-extent raw LAS v1.4 swaths, classified point cloud LAS v1.4 files formatted to 3817 individual 1,500 m x 1,500 m tiles in NAD83 (2011), UTM Zone 15N, Meter. Derivatives were produced as tiled; Bare Earth Surface DEMs, Digital Surface Models, Intensity Images; all tiled to the same 1,500 m x 1,500 m schema.

Ground conditions: Lidar was collected in Winter of 2017 by Aerial Services, Inc. (ASI), and WOOLPERT. The Chenier Plain Wetland areas contain hundreds of impoundments related to aquaculture operations. These fields are flooded and contained within the impoundments on a semi-permanent basis, including during the Chenier Plain lidar acquisition timeframe. This is an understood and accepted acquisition condition. Furthermore, impoundments equal to or greater than 2 acres are treated as hydrologically flattened features within the data deliverables. Tidal Restriction: The following tide gauges were considered suitable for prediction of regional water levels within the AOI; Sabin Pass North, TX NOS (8770570), Calcasieu Pass, LA NOS (8768094), Freshwater Canal Locks, LA NOS (8766072), and Amerada Pass, LA NOS (8764227). Water levels at flight time shall were below -0.10 meters (mean seal level) for the Calcasieu Pass, LA tide gauge (8768094) in the west and -0.10 meters (mean seal level) for the Amerada Pass, LA tide gauge (8764227). Meteorological: Acquisition did not occur after passage of a moderate to strong high-pressure system generating northerly winds in excess of five (5) knots. In addition, it is noted switching of winds from WNW to ENE is a tipping point for switching from wind driven marsh drainage to marsh flooding. Ground Conditions: Within the extreme eastern AOI (swamp and fresh to intermediate marsh occurring northeast of Marsh Island and bordering East Cote Blanche Bay) Lidar was not acquired when the Lower Atchafalaya River stage was less than 4 feet as determined by the latest measurements taken at gauge (USGS 07381605) at Morgan City.

Lidar was not acquired when regional precipitation driven flooding occurred in local rivers with significant impact to wetland impoundments located throughout the entire Chenier Plain west of Cote Blanch Bay. The following local rivers shall be monitored for flood conditions; Vermillion, Mermentau, Calcasieu, and Sabine rivers. In order to post process the lidar data to meet task order specifications and meet ASPRS vertical accuracy guidelines, Woolpert established a total of 68 ground control points that were used to calibrate the lidar to known ground locations established throughout the project area. Additional independent accuracy checkpoints were collected (94 NVA points and 75 VVA points) and used to assess the vertical accuracy of the data. These checkpoints were not used to calibrate or post process the data.

The NOAA Office for Coastal Management (OCM) downloaded the LA_Chenier_Plain_2017 Digital Elevation Model (DEM) files from this USGS site: ftp://rockyftp.cr.usgs.gov/vdelivery/Datasets/Staged/Elevation/OPR/ and processed the data to the Data Access Viewer (DAV) and https.

In addition to these bare earth Digital Elevation Model (DEM) data, the lidar point data that these DEMs were created from, are also available. These data are available for custom download at the link provided in the URL section of this metadata record.

Hydro breaklines are also available. These data are available for download at the link provided in the URL section of this metadata record. Please note that these products have not been reviewed by the NOAA Office for Coastal Management (OCM) and any conclusions drawn from the analysis of this information are not the responsibility of NOAA or OCM.

The Chenier Plain QL2 light detection and ranging (lidar) acquisition updates 15+ year old QL4 equivalent topographic lidar for an area representing approximately half of the Mississippi River Delta Plain Complex. The Chenier Plain has incurred direct-surge induced wetland loss impacts from Hurricane Rita (2005) and from Hurricane Ike (2008) as well as economic losses to the local population and surrounding areas. The lidar update will provide an elevation base for assessing current conditions as well as providing a solid data platform for monitoring the impacts of future episodic events, from tropical cyclones or other potential inundation events within the region.

Raster File Type = TIFF Bit Depth/Pixel Type =32-bit float Raster Cell Size = 1 Meter Interpolation or Resampling Technique = Triangulated Irregular Network Required Vertical Accuracy = NVA