Lidar-derived Hydrography as a Source for the National Hydrography Dataset

Transcription

1 Lidar-derived Hydrography as a Source for the National Hydrography Dataset Lidar-Derived Hydrography, Bathymetry, and Topobathymetry in the National Hydrography Dataset and 3-Dimensional Elevation Program March, 2017 Cynthia Miller-Corbett

2 2 Light detection and ranging Lidar-derived Hydrography and Topography to provide Bathymetry and Topobathymetry U.S. Geological Survey, The National Map, National Hydrography Dataset Experimental Advanced Airborne Research Lidar Sensor System and Airborne Lidar Processing Bathymetry: Measure of depth to water feature bottom surface Topobathymetry: Merged rendering of bathymetry and topography

3 3 Delaware River EAARL-B Survey: Locations and Flight Paths Hancock Narrows Group Middle River Group Trenton Group Lidar survey groups: Hancock Narrows; Middle River; Trenton. Flight paths for Delaware River image acquisition, Gayla Evans, EROS, 2016

4 4 Channel Extraction Creating Synthetic Flowlines Terrain Pre-processing Applications 1-meter, 5-meter, and 10-meter resolution Lidar Digital Elevation Model Fill Sinks Number of grid cells required to flow to a grid cell for it to be a Stream Segment Flow Accumulation Threshold D8 Flow Direction Grid Flow Accumulation Stream Definition Stream Segments Catchment Grid Drainline Processing Catchment Polygon D8 Flow Direction Grid for Hydrological Digital Elevation Model (DEM)

5 +Integrating Bathymetric and Topographic Elevation Data µ Smooth transition with differences concentrated at river bends Kilometers Source: Esri, DigitalGlobe, GeoEye, Earthstar Geographics, CNES/Airbus DS, USDA, USGS, AeroGRID, IGN, and the GIS User Community Hancock Narrows Group Percent Difference Contoured Elevation Differences for Hancock Narrows Group Lidar Survey and 3DEP DEMs Contoured differences for 3DEP lidar DEMs and Delaware River bathymetric lidar data meter Contour Difference [Approximately 1/6 arc-second (5-meter resolution)] 5

6 6 Topobathymetry - Slope to Channel Bottom Without Gaps Processed green and near-infrared waveform data map transition from Topographic to Bathymetric Terrain 30+% Slope 15% Slope

7 7 Synthetic Flowlines derived from for Hydrologic Digital Elevation Model at 3 Resolutions [FAC, Flow Accumulation Threshold; Max FAC, Maximum Flow Accumulation based on Stream Definition Value; NHD, National Hydrography Dataset]

8 8 Site Conditions: Effects of Flat Terrain and In-Channel Island 1-meter Cell size 5-meter Cell size 10-meter Cell size 1-Percent Maximum Flow Accumulation Cell Size (meter) Cell Count Stream Segment Area (meters2) 1 87,000 87, , , , ,300 1-meter cell size: Discontinuous river channel Isolated synthetic flowline correlative to part of 5m and 10m resolution data synthetic flowlines Synthetic flowline on north side of inchannel island 5-meter and 10-meter cell size: Continuous river channel on southwest side of in-channel island

9 9 10-meter Grid-cell Spacing: Variable Stream Segment development for Synthetic Flowlines Increase in Stream Segment Density and Connectivity with decrease in Flow Accumulation Threshold values Percent of Maximum Flow Accumulation Flow Accumulation Threshold (cells) Stream Segment Area (m 2 ) , , ,000

10 10 Channel Extraction from Topobathymetric Lidar Data at 0.05-Percent of Maximum Flow Accumulation 1-meter resolution 5-meter resolution 10-meter resolution 0.05-Percent Maximum Flow Accumulation Cell Size (meter) Cell Count Stream Segment Area (meters 2 ) 1 6,814 6, , ,700 1-meter resolution: Synthetic flowline on both sides of in-channel island and no trellis pattern in area of alternating flow directions West-side tributary connected to river channel 5-meter and 10-meter resolution: West-side tributary disconnected from river channel Trellis pattern upstream of relatively shallow river bottom

11 11 Site conditions Difficulties for traditional surface-water algorithms to model flow Alteration of surface-water flow reflected in developed synthetic flowlines Channel conditions behind human-made and natural obstructions causing issues with the. network generation algorithms. In this case, a trellis pattern forms. The deeper pool behind the shallower obstruction is filled/raised by the algorithm to generate a flat surface and develops parallel trellis pattern flowlines as shown here. Steps can be taken when these conditions exist such as burning a trench through the center of the weir or directing the flowline through the lock located on the left side of this feature

12 12 Correlation lidar-derived hydrography and High Resolution National Hydrography Flowline Network Good correlation and potential for adding stream/river features Offset of river channel center-line with 5- and 10-meter synthetic flowlines delineating linear bathymetric low on the outside of a river bend [ O, correlation of NHD flowline and lidar-derived hydrography]

13 13 Results for evaluating of lidar hydrography as a source for the National Hydrography Dataset Flowline Network The National Geospatial Program is still building a foundation of knowledge regarding these technologies and techniques and has not committed to formalizing any of the potential uses. Results for this preliminary evaluation for using lidarderived hydrography as a source for the National Hydrography Dataset indicate some potential future uses including: Improved National Hydrography Dataset Flowline feature geometries; Better integration of elevation and hydrography Adding river channel thalweg lineaments as a new feature type Slope to river bottom transitions without gaps for Coastal Zone and Inland surface water features Improved connectivity for the National Hydrography Dataset Flowline Network Enhanced densification of flowline feature types Trenton Group, south side of Eagle Island, New Jersey

14 14 Questions?