evaluating lidar derived synthetic streams as a source for national hydrography dataset flowlines

1. +
September, 2016
Cynthia Miller-Corbett,
U.S. Geological Survey
Evaluating
Lidar-derived
Synthetic Streams as
a Source for
National Hydrography
Dataset Flowlines

2. + 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 surface
Topobathymetry: Merged rendering of bathymetry and topography

3. + 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. + 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

5. + 5
Integration of Lidar-Derived Topobathymetry and
3D Elevation Program Digital Elevation Model
0
5
10
15
20
25
30
-6 -4 -2 0 2 4 6 8 10 12 14 16 18
PercentDifference
2-meter Contour Difference
Contoured Elevation Differences for
Hancock Section
Lidar Survey and 3DEP DEMs
Smooth
transition with
differences
concentrated at
river bends.

6. + 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.
15%

7. + 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 Bathymetry
Trellis-pattern drainage

8. + 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 Applications
Data Input - Lidar Digital Elevation Model

9. + 9
Flow 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 Hydrography
1% 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. + 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

11. + 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. + 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. + 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. + 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. + 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. + 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

17. + 17
Lidar-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.