+

September, 2016Cynthia Miller-Corbett, U.S. Geological Survey

Evaluating Lidar-derived Synthetic Streams as a Source for National Hydrography Dataset Flowlines

+ 2

Lidar-derived Bathymetry and Topobathymetry in the National Hydrography Dataset

Green light waveform lidar system. Read more: http://coastal.er.usgs.gov/lsrm/tech/tech2-alps.html

National Hydrography Dataset.Read more: http://nationalmap.gov/ and http://nhd.usgs.gov/

Bathymetry: Measure of depth to water feature bottom surfaceTopobathymetry: Merged rendering of bathymetry and topography

+ 3

Comparison of developed synthetic stream/river feature data with National Hydrography Dataset (NHD) flowlines provides a qualitative assessment of benefits and issues for using lidar-derived hydrography as a source to enhance NHD surface-water features.

Differences between the two datasets are evaluated against orthoimagery and lidar-derived 3DEP DEMs to determine:

• Does the synthetic hydrography provide better delineation of real stream/river features?

• Where synthetic hydrography provides better delineation, are differences between datasets greater than NHD accuracy standards, indicating NHD Flowline data require updating?

• Do synthetic drainlines provide connectivity with NHD Flowlines?

• Do individual synthetic drainlines stay within the Watershed Boundary Dataset as required for developing catchments and watersheds?

• Are differences between datasets a consequence of terrain or medium?

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

+ 4

The EAARL-B is a full-waveform lidar system.• Green- light (532 nm) laser

capable of 20-meter (clear water) depth penetration

• Terrestrial and aquatic mapping capabilities

Data processing steps occur within the custom-built Airborne Lidar Processing System (ALPS) (Bonisteel and others, 2009), as does the point correspondence procedure

Flight paths for Hancock-Trenton sections of Delaware River image acquisition, Gayla Evans, EROS, 2016

EAARL-B Lidar System

+ 5Integration of Lidar-Derived Topobathymetry and 3D Elevation Program Digital Elevation Model

-6 -4 -2 0 2 4 6 8 10 12 14 16 1805

1015202530

Contoured Elevation Differences for Hancock Section

Lidar Survey and 3DEP DEMs

2-meter Contour Difference

Perc

ent D

iffer

ence

Smooth transition with differences concentrated at river bends.

+ 6

Inland Topobathymetry: Slope to Channel Bottom Without Gaps

Cross-section profile shows processed lidar data clearly map steep bank slopes, merging lidar topography and bathymetry.

Hancock Suite, Steep River Banks

Distance (meters)240220200180160140120100806040200

Ele

vatio

n (m

eter

s)

277

276

275

274

273

272

271

270

269

268

267

15%

+ 7

Trellis-pattern drainage that in cross-sectional profile reveal a corrugated river bed where bathymetry differs less than 1 meter.

Drainage Lines for In-Channel BathymetryTrellis-pattern drainage

+ 8

Flow Direction Grid for lidar digital elevation model

Developing Lidar-Derived Stream/River Features (Drainlines) Flow Accumulations and Stream Threshold

Drainline Processing

Fill Sinks

Flow Direction

Catchment Polygon

Stream Segments

Catchment Grid

Stream Definition

Flow Accumulation

Terrain Pre-processing ApplicationsData Input - Lidar Digital Elevation Model

+ 9Flow Accumulation Threshold for Lidar-Derived Synthetic Drainlines for 1:24,000-scale National Hydrography Dataset

1-Meter Resolution Dataset 100 to 120 miles of Delaware River Survey

Max FAC: 8,700,675

5-Meter Resolution Dataset 100 to 120 miles of Delaware River Survey

Max FAC: 321,115

FAC Lidar-derived Hydrography FAC Lidar-derived Hydrography1% Max FAC(87,000)

River channel with disconnected around islands; no tributaries (160 synthetic drainlines)

1% Max FAC(3212)

Disconnected river channel; a few connections with tributaries (136 synthetic drainlines)

0.3% Max FAC(25,000)

River channel discontinuous; good correlation with tributaries as well as additional lower order streams (656 synthetic drainlines)

0.3% Max FAC (1000)

River channel discontinuous; some good connections with tributaries (704 synthetic drainlines)

0.02% Max FAC (1500)

River channel discontinuous; too many synthetic streams (15,406 synthetic drainlines)

0.16% max FAC (500)

River channel discontinuous; some good connections with tributaries; isolated drainlines (1448 synthetic drainlines)

FAC, Flow Accumulation Threshold; Max FAC, Maximum Flow Accumulation based on Stream Definition Value

Results for initial analysis indicate using 1% or less than Maximum Flow Accumulation value will provide best results.

+ 10

5-Meter Grid-spacing1-Meter Grid-spacing 10-Meter Grid-spacing

Grid Spacing(meter)

1 Percent of Maximum Flow Accumulation for All Sinks Filled

1 87,000

5 3,212

10 3,623

Lidar-derived Drainlines using 1 Percent of the Maximum Flow Accumulation for 1-m, 5-m and 10-m Gridded Trenton Group

Evaluating Lidar-Derived Hydrography at Different Grid Spacing

+ 11Trenton Group: Lidar-derived Hydrography at Variable Cell-Size using 1 Percent Maximum Flow Accumulation

Stream Definition for 1 Percent of Maximum Flow Accumulation: Better at larger gridding

Possible reason for difference in drainlines• Fewer synthetic drainlines are

connected due to larger stream definition

• Site Conditions, where flat surface at river bend may be better detected at smaller resolution, preventing connected drainline development

Grid Spacing(meter)

1 Percent of Maximum Flow Accumulation for All

Sinks Filled

1 87,000

5 3,212

10 3,623

+ 12

0.05 Percent of Maximum Flow Accumulation

Number of Drainlines

1-Meter: Drain7K 2492

5-Meter: Drain500 1282

10-Meter: 10Sept10mHan150 1011

Derived Hydrography using 0.05 Percent of Maximum Flow Accumulation for 1-meter, 5-meter, and 10-meter Grid Cells

1-Meter Data:• Trellis Pattern not developed• Additional Flowlines• Disconnected in flat topography

Correlation with the National Hydrography Dataset at Variable Grid-Spacing

+ 13

Threshold of 150 (0.04%) creates 1,275 Drainlines

Threshold of 500 (0.13%) creates 305

Drainlines

Threshold of 250 (0.07%) creates 717 Drainlines

Differences for Synthetic Streamline Density at 10-meter Resolution and Variable Stream Threshold Values

+ 14

5-Meter Hancock Group, 0.04% of maximum Flow Accumulation Value(1,333,351)

Correlation of Lidar-Derived Synthetic Streams and the National Hydrography Dataset Flowline Network

+ 15

Synthetic drainlines may provide additional 2nd and higher order streams based on required drainline density.

Trenton section, south side of Eagle Island, New Jersey

Lidar-Derived Hydrography Improvements to Surface-Water Features

Synthetic bathymetry and topobathymetry delineating flowpaths can enhance depiction of river channel positions currently identified in the NHD by Artificial Paths, and provide channel geometry

+ 16

Hydrologic and Hydraulic framework: Drainage lines form the skeletal framework for deriving flow paths and flow directions fundamental to water supply analyses and modeling.

Water resource management organizations that rely on estimating water supplies important to;• population centers,• wildlife and range management, • water resource management and

protection, • floodplain modeling,• agricultural enterprises, and the • energy industry.

Significance of Integration of Lidar-Derived Hydrography for Surface-Water Feature Mapping

Lidar image and profile across Delaware River

+ 17Lidar-Derived Hydrography in the National Geospatial Program

Lidar-derived hydrography and NHD artificial paths for river channels

Test results show that lidar-derived hydrography can provide a source for data in the National Hydrography Dataset (NHD) to enhance flowline density that can;• Better depict first and higher order streams,• Provide improved connectivity for the NHD Flowline Network,• Provide smooth transitions between coastal zone or inland

surface water features and 3DEP topography,• Improve NHD Flowline accuracy,• Map thalweg for river channels to enhance delineation where

these are identified using NHD Artificial Paths, and• Meet 3DEP goal to provide 3-dimensional data for the United

States

Developing synthetic flowlines at different resolutions and variable Flow Accumulation (FAC) values indicates:• Threshold values of 1 percent or less of the

Maximum FAC at 1, 5, and 10 meter grid-spacing create river channel and tributary lineaments that often correlate and connect with NHD Flowlines.

• Higher order streams may be developed using smaller FAC values to develop the required density of flowlines.

• Site conditions may affect synthetic flowlines derived at different grid spacing and FAC threshold values.