The Texas Shoreline Change Project: The Texas Shoreline Change Project: Combining Lidar, Historical Photography, and Ground Surveys to Measure Shoreline

The Texas Shoreline Change Project:The Texas Shoreline Change Project:

Combining Lidar, Historical Photography, and Ground Surveys to Measure Shoreline Change Rates along Bay and Gulf of Mexico Shorelines

James C. Gibeaut, William A. White, Roberto Gutierrez, Rachel Waldinger, John R. Andrews, Tiffany L. Hepner,

Rebecca C. Smyth, and Thomas A. Tremblay

Bureau of Economic Geology

John A. and Katherine G. Jackson School of Geosciences

The University of Texas at Austin

Shoreline Shoreline LengthLength

Gulf = 600 kmGulf = 600 km

Bays = 9,400 kmBays = 9,400 km

• Mapping past and current shorelines

– Aerial photography

– Ground kinematic GPS

– Airborne lidar – shoreline plus beach and dune topographic mapping

• Calculating “average annual rate of change” and projecting future shoreline position

– GIS-based Shoreline Shape and Projection Program (SSAPP)

• Beach profile ground surveys

• Data availability and public awareness

– Online reports

– Web-based GIS using ArcIMS software

Project ComponentsProject Components

Data SourcesData Sources

Before 1930:Maps from the mid to late 1800’s produced by the U.S. Coast Survey – “high-water line mapped.”

Generally not used:Engineering structures altered sediment budget since 1900.

Sand Trapped by Jetty, Southwest end of Bolivar Peninsula (08/07/98)


1930’s to 1990’s - Vertical Aerial Photographs

Digital Photo RectificationDigital Photo Rectification

1995 Digital 1995 Digital Orthophoto Orthophoto Quarter Quads Quarter Quads Serve as Base Serve as Base MapsMaps

•USGS/Tx Orthophoto Program

•Scanned color IR film, 1-m resolution

•Meet 1:12,000 map accuracy standards (90% of test points within10 m)

•Our tests show typically within 5 m

Shoreline InterpretationShoreline InterpretationWet/Dry LineWet/Dry Line

Gulf of Mexico

Matagorda Bay

Shoreline InterpretationShoreline InterpretationShoreline and Vegetation LineShoreline and Vegetation Line

Shore andvegetation line


• Mapping shorelines








– Online reports


1990’s – Kinematic GPS Surveys











– Online reports


• Mirror sweeps laser beam across the ground.

• Range to target is determined by measuring time interval between outgoing and return of reflected laser pulse.

• Aircraft position is determined using GPS phase differencing techniques.

• Pointing direction of laser determined with Inertial Measuring Unit (IMU) and recording of mirror position.

• Data streams recorded and synchronized for post processing.

GPS ground reference station

Aircraft GPS

GPS satellites

Flight direction

ALTM laser and IMU

Airborne Topographic LidarAirborne Topographic Lidar

GPS Coastal NetworkGPS Coastal Network

GPS base station locationswith 50-km radius circles

Texas Study area

SABP

PTBO

USCG

MATAPTOC

PTAR

QAIL

PTMN

SPAD

Mouth ofRio Grande

Laguna Madre

Matagorda Bay

Corpus Christi Bay

GalvestonBay

SABP U.S. Coast Guard Station, Sabine Pass

PTBO Port Bolivar Tide Gauge

USCG U.S. Coast Guard Station, Freeport

MATA Matagorda Jetty Park, USACE mark

PTOC Port O'Connor Tide Gauge

PTAR Port Aransas

QAIL Padre Island National Seashore

PTMN Port Mansfield Tide Gauge

SPAD U.S. Coast Guard Station, South Padre Island

100 km0

0 50 100 mi

Beach profiles

Lidar Instrument in Cessna 206Lidar Instrument in Cessna 206Optech ALTM 1225Optech ALTM 1225

MHHW +0.6 m msl Geotube

Landward boundaryBEG-02

Beach profile

QAd496Gibeaut_CCC_Jan31_2002

Lidar Digital Elevation ModelLidar Digital Elevation Model1 - m grid1 - m grid

• Ellipsoidal heights converted to orthometric heights (NAVD 88) using GEOID99 gravity model.

• Local mean sea level (MSL) correction applied.

Calibration TargetCalibration Target

Calibration Flight LinesCalibration Flight Lines

0 2 mi

2 km0

Gulf of Mexico

Kinematic surveydata points

Calibration aircrafttrajectory

Shoreline aircrafttrajectory

Galvestoncounty roads

Environmentalsensitivity index

Lidar Survey VideoLidar Survey Video

Galveston BeachGalveston Beach

Wet/Dry Line

Galveston Island ProfileGalveston Island Profile

Lidar last return

Total station ground survey

Lidar last return intensity

Vertical exaggeration 50

Geotube

Vegetation

Monument

Wet/dry line

Water surface

+0.6 m above MSL

0

50

100

150

200

250

300

350

400

–200 –150 –100 –50 0 50 100 150 200 250Distance from monument (m)

–30

–29

–28

–27

–26

–25

–24

Representative Wet/Dry ElevationRepresentative Wet/Dry Elevation0.6 m along Upper Tx Gulf Coast0.6 m along Upper Tx Gulf Coast

0

1

2

3

-1

-2

0.6MHHW

0 100

Hei

ght r

e la t

ive

to M

SL

(m)

Distance (m)

50

upper berm crest

vegetation line

Why Use a Wet/Dry Why Use a Wet/Dry Elevation?Elevation?

• Consistent with historical photography.

• Consistent with 2d ground GPS surveys.

• Lidar can measure reliably even during elevated water levels.

• Geomorphologically significant elevation not as susceptible to short-term erosion/depositional cycles compared to lower elevations.

Hand-Smoothed ShorelineHand-Smoothed Shoreline










– Online reports


Shoreline Shape and Shoreline Shape and Projection ProgramProjection Program

ArcView InterfaceArcView Interface

-250

-200

-150

-100

-50

0

50

100

150

200

1840 1860 1880 1900 1920 1940 1960 1980 2000 2020 2040 2060

Shoreline

Long-term end point rate

Mid-term/linear regression rate

Year QAb5370c

BureauofEconomic

Geology

Shoreline Change RateShoreline Change Rate

Projected ShorelineProjected ShorelineGalveston IslandGalveston Island










– Online reports


Ground SurveyGround Survey

Beach ProfileBeach ProfileAnnotatedAnnotated










– Online reports


www.beg.utexas.edu/coastalwww.beg.utexas.edu/coastalwww.beg.utexas.edu/coastalwww.beg.utexas.edu/coastal

Documents

The Texas Shoreline Change Project: The Texas Shoreline Change Project: Combining Lidar, Historical Photography, and Ground Surveys to Measure Shoreline