Quantifying Coastal Evolution using Remote Sensing Approaches

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Claire Bridges
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Gallagher University College Dublin Geological Survey of

1 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

2 Content Context and Objectives Study area Methodology and Data Sources Initial Results Discussion Summary

3 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

4 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

5 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 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 changerates and sediment budgets, the landform changes observed and an assessment of major geomorphic controls.

6 Study Area (

7 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

8 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

9 Delineation of Shoreline positions

Shoreline Change Rates Digital Shoreline Analysis Baseline parallel to historic shorelines Transect generation at 20 m interval Shoreline change rate

10 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

11 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

12 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

13 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.

14 Laser Point Cloud data along Distal End of Murvagh Peninsula GCP Error X (m) Error Y (m) Error Z (m) Mean SD

15 Automatic Geomorhphic Feature Extraction Crest line Toe line High Waterline

CACULATED HEIGHT DELTA X DELTA Y DELTA Z 553897.54 6052109.34 8.96 553897.562 6052109.

16 Aerial Drone (UX5HP) Survey - Initial Results 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

Coastal Reaches of Interest & Internal Architecture Geomorphological mapping and geophysical characterization to better understand the beach dune evolution processes and stratigraphic as well as

17 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

18 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

20 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

21 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.

22 References: Houser, C. Mathew, S Alongshore variation in foredune height in response to transport potential and sediment supply: South Padre Island, Texas. Geomorphology, 125, Mathew, S., and Davidson-Arnott, R.G.D., Ollerhead, J Evolution of a beach-dune system following a catastrophic storm overwash event: Greenwich Dunes, Prince Edward Island, Canadian Journal of Earth Science, V47, no. 3, p

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