THE TEXAS SHORELINE CHANGE PROJECT: COMBINING LIDAR, HISTORICAL PHOTOGRAPHY, AND GROUND SURVEYS TO MEASURE SHORELINE CHANGE RATES ALONG BAY AND GULF James C.
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THE TEXAS SHORELINE CHANGE PROJECT: COMBINING LIDAR, HISTORICAL PHOTOGRAPHY, AND GROUND SURVEYS TO MEASURE SHORELINE CHANGE RATES ALONG BAY AND GULF 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 Funding from GLO, NASA, and MMS Texas Coastal Issues Conference 2004
Shoreline Length Gulf = 600 km Bays = 9,400 km
Project Components
• • • •
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
Data 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)
Data Sources
1930’s to 1990’s - Vertical Aerial Photographs
Zoom-Transfer Scope
Digital Photo Rectification
1995 Digital Orthophoto Quarter Quads Serve as Base Maps
•
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 Interpretation
Wet/Dry Line
Matagorda Bay Gulf of Mexico
Shoreline Interpretation
Shoreline and Vegetation Line Shore and vegetation line
Project Components
• • • •
Mapping 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
Data Sources
1990’s – Kinematic GPS Surveys
Project Components
• • • •
Mapping 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
Airborne Topographic Lidar
• • • • • 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.
ALTM laser and IMU GPS satellites Aircraft GPS La se r s ca n lin es GPS ground reference station Flight direction
GPS Coastal Network
Texas Study area 0 0 50 100 km 100 mi SABP PTBO USCG PTAR PTOC MATA
Matagorda Bay Corpus Christi Bay
QAIL PTMN
Laguna Madre Mouth of Rio Grande Galveston Bay
Beach profiles GPS base station locations with 50-km radius circles 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 SPAD
Lidar Survey Video
Lidar Digital Elevation Model
1 - m grid BEG-02 Beach profile Landward boundary MHHW +0.6 m msl Geotube
• •
Ellipsoidal heights converted to orthometric heights (NAVD 88) using GEOID99 gravity model.
Local mean sea level (MSL) correction applied.
Gibeaut_CCC_Jan31_2002
QAd496
Galveston Beach
Wet/Dry Line
Lidar Intensity Draped on Topography
Galveston Island Profile
–24 –25 –26 –27 –28 Monument Vegetation Geotube +0.6 m above MSL Wet/dry line Water surface –29 –30 –200 –150 Lidar last return Total station ground survey Lidar last return intensity Vertical exaggeration
50 –100 –50 0 50 100 Distance from monument (m) 150 200 100 50 250 0 400 350 300 250 200 150
3 2 1 0 -1 -2 0
Representative Wet/Dry Elevation
0.6 m along Upper Tx Gulf Coast vegetation line upper berm crest
0.6
MHHW 50 Distance (m) 100
Why Use a Wet/Dry 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.
Project Components
• • • •
Mapping 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
Shoreline Shape and Projection Program
ArcView Interface
Shoreline Change Rate
200 150 100 50 Mid-term/linear regression rate 0 Shoreline -50 -100 Long-term end point rate -150 -200
Bureau of Economic Geology
-250 1840 1860 1880 1900 1920 1940 1960 1980 2000 2020 2040 2060
Year QAb5370c
Projected Shoreline
Galveston Island
Shorelines Used Upper Texas Gulf Coast
• • • • • • • •
1930 – Optical mapping and transfer to base map 1956 – Optical mapping and transfer to base map 1965 – Optical mapping and transfer to base map 1974 – Digital rectification and mapping 1982 – Digital rectification and mapping 1990 – Optical mapping and transfer to base map 1995/96 – Digital Orthophotos 2000 - Lidar
Digital Rectification Accuracy Comparison with Lidar Points 1974 photos: Standard Deviation= 6.62 ft , 60 pts. Compared 1982 photos: Standard Deviation= 5.51 ft , 97 pts. Compared Probably at least 5 times more accurate than optical methods.
Project Components
• • • •
Mapping 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
Long-Term Shoreline Change West Beach Galveston Island (Calculated using multiple shorelines from 1930 to 2000.) # ## ##### # # ## ### ## ### ### #### ### # # #### #### ## #### ## ##### # #### #### #### #### ### #### 1 ##### #### 0 #### ##### #### # ##### #### #### # N 1 ##### #### ##### #### ##### ##### #### ### #### # 2 3 Miles ##### #### ##### ##### ## ##### #### # ##### ##### #### ##### # #### ##### #### #### #### # #### ##### #### # ## ##### ##### # # # # # # # # # # # # # # # # # # # Shoreline Change Rate (ft/yr) -10.6 - -10.1
-10.1 - -9.6
-9.6 - -9.1
-9.1 - -8.6
-8.6 - -8.2
-8.2 - -7.7
-7.7 - -7.2
-7.2 - -6.7
-6.7 - -6.2
-6.2 - -5.7
-5.7 - -5.2
-5.2 - -4.7
-4.7 - -4.3
-4.3 - -3.8
-3.8 - -3.3
-3.3 - -2.8
-2.8 - -2.3
-2.3 - -1.8
-1.8 - -1.3