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  • 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 OToole, 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.

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