Quantifying Coastal Evolution using Remote Sensing Approaches
Sojan Mathew, Linh Truong Hong, Xavier Pellicer*,
Colman Gallagher University College Dublin
Geological Survey of Ireland*
INFOMAR SEMINAR, Marine Science Institute, Galway
October 19, 2016
Content
• Context and Objectives
• Study area
• Methodology and Data Sources
• Initial Results
• Discussion
• Summary
Context
• Advances in Sensor Technologies and computational breakthroughs
• Highly accurate and spatially dense topographic and internal architecture of beach dune system
• Reconstruction of past beach dune configuration using
• Photogrammetry and geophysical approaches • Large Scale Historic Aerial Photos + • Applications of RS, GIS & DGPS • 2D/3D Analysis and Sediment Budget • Viable technique for Coastal Evolution Studies
Problem & Objectives
• Objectives: Quantify the evolution of Murvagh Peninsula along Donegal bay using remote sensing approaches
• Geomorphological mapping and geophysical characterization to better understand the beach dune evolution processes and stratigraphic as well as hydrostratigraphic units of Murvagh Peninsula along Donegal bay
Specific Objectives • To evaluate the shoreline change-rates and areal change-rate of
geomorphic units along Murvagh peninsula over the past seven decades based on historic aerial photos and field surveys
• To develop algorithms for automatic extraction of geomorphic features such as low water line, high water line, toe line and crest shoreline
• To evaluate the changes in volume and beach dune sediment budget within the study area in light of shoreline evolution over the period 1950 – 2013.
• Linking shoreline changes and beach dune morphodynamics to nearshore bathymetry;
• To develop conceptual model of the future evolution of Murvagh peninsula based quantitative measurements of shoreline change-rates and sediment budgets, the landform changes observed and an assessment of major geomorphic controls.
Study Area
(www.met.ie/wind.asp)
Data Sources
• Historic Aerial images • Aerial lida data • Terrestrial lidar data • RTK GPS survey data • Drone based imagery & DEM • Multi-beam Echo Sound data • Ground Penetrating Radar data • Electrical Resistivity Tomography
Methods
• Geomorphological Mapping
• Historic Aerial Photos/DEMs
• Shoreline Change rates
• Digital Shoreline Analysis System (DSAS)
• Geophysical Characterisation
• GPR, and ERT
• Internal architecture of beach dune system
• Stratigrafic and Hydrostratigraphic units
Delineation of Shoreline positions
Shoreline Change Rates
• Digital Shoreline Analysis
• Baseline parallel to historic shorelines
• Transect generation at 20 m interval
• Shoreline change rate calculation based o LRR/EPR
• Erosion/Accretion hotspots
• Prediction of future shoreline position based on historic shoreline change rates –
• Pros and Cons – weighted mean approach
Aerial Change in Geomorphic Units
• Based on geomorphologic characteristics - 2D mapping of
• Beach Intertidal zone
• Aeolian sand dunes
• Modified Aeolian sand dunes
• Inland dunes
• Salt marshes
• Forest
• Grasslands
• Building & parking lot
Volumetric change & Sediment Budget
• Inflow, out flow and through flow and net deposition
• RTK GDPS Survey • Mapping vegetation line • Crestline, Low water line • Shore normal transects at
200 m interval • Volume of sediment
available across beach dune area
• Volumetric change change analysis with 2008 aerial lidar DEM
• Aerial Drone DEM • Terrestrial laser scan DEM
High Resolution Terrestrial Laser Scan Data
Laser Point Cloud data along Distal End of Murvagh Peninsula
GCP
Error X
(m)
Error Y
(m)
Error Z
(m)
1 0.12 0.18 0.04
2 0.07 0.15 0.05
3 0.24 0.11 0.02
4 0.09 0.13 0.03
5 0.18 0.28 0.00
6 0.22 0.09 0.08
7 0.15 0.08 0.04
8 0.11 0.08 0.10
9 0.17 0.21 0.08
10 0.13 0.08 0.06
Mean 0.15 0.14 0.05
SD 0.05 0.06 0.03
Crest line
Toe line
High Waterline
Automatic Geomorhphic Feature Extraction
The resolution of the DSM/orthomasic is 3.82cm UTM
EASTING
UTM
NORTHING
Height
CALCULATED
EASTING
CALCULATED
NORTHING
CACULATED
HEIGHT
DELTA
X
DELTA
Y
DELTA
Z
553897.54 6052109.34 8.96 553897.562 6052109.338 8.967 -0.02 0.00 0.00
553823.29 6052414.28 11.01 553823.29 6052414.282 11.025 0.00 0.00 -0.02
Aerial Drone (UX5HP) Survey - Initial Results
Coastal Reaches of Interest & Internal Architecture
• Geomorphological mapping and geophysical characterization to better understand the beach dune evolution processes and stratigraphic as well as hydrostratigraphic units of Murvagh Peninsula along Donegal bay
• Site 1: High dunes, low accretion rate, large sediment supply
• Site 2: Low dunes, high accretion rates – drumlin
• Site 3: Low dunes, high erosion rates, glacial till
Discussion
• Accuracy of Geomorphic mapping
• Shoreline accretion rates – future trend
• Major controls on accretion rates
• Sediment supply, circulation pattern, dominant wind direction
• Hydrodynamic + Aerodynamic processes
• Anthropogenic activities vs. Extreme events
• Current status and future evolution
• Limitations of geophysical approaches
Conclusion
• Combination of RS approaches - historic aerial photos, DEMs, GPS and GPR, ERT , MBES
• Geomorphological mapping
• Characterize surface/subsurface processes and forms coastal evolution
• Shoreline change rates – prediction
• Beach dune morphodynamics and linkages to nearshore bathymetry
Acknowledgement
Authors would like to thank Donal Lennon from Earth Institute, UCD for helping us with the collection of terrestrial lidar data. We would also like to thank David Hardy, Xavier Pellicer, Xavier Monteyes, Ronan O’Toole, and Nial Finn from GSI for their invaluable help during the data collection and processing stages.
References: Houser, C. Mathew, S. 2011. Alongshore variation in foredune
height in response to transport potential and sediment supply:
South Padre Island, Texas. Geomorphology, 125, 62-72.
Mathew, S., and Davidson-Arnott, R.G.D., Ollerhead, J. 2010. Evolution of a beach-dune system following a catastrophic storm overwash event: Greenwich Dunes, Prince Edward Island, 1936-2005. Canadian Journal of Earth Science, V47, no. 3, p. 273-290.
