An Investigation into Ground Movement on the Ventnor Landslide Complex, UK Using Persistent Scatterer Interferometry

Analysis of ground movement rates along the coastline and upper sections of the Ventnor landslide complex was carried out utilizing Persistent Scatterer Interferometric Synthetic Aperture Radar methods using Sentinel-1 SAR data from 2015 to 2019 (four years). Results were compared with rainfall data...

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Main Authors: William O’Connor, Gosia Mider, James A. Lawrence, Stewart Agar, Philippa J. Mason, Richard Ghail, Jennifer Scoular
Format: Article
Language:English
Published: MDPI AG 2021-09-01
Series:Remote Sensing
Subjects:
Online Access:https://www.mdpi.com/2072-4292/13/18/3711
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author William O’Connor
Gosia Mider
James A. Lawrence
Stewart Agar
Philippa J. Mason
Richard Ghail
Jennifer Scoular
author_facet William O’Connor
Gosia Mider
James A. Lawrence
Stewart Agar
Philippa J. Mason
Richard Ghail
Jennifer Scoular
author_sort William O’Connor
collection DOAJ
description Analysis of ground movement rates along the coastline and upper sections of the Ventnor landslide complex was carried out utilizing Persistent Scatterer Interferometric Synthetic Aperture Radar methods using Sentinel-1 SAR data from 2015 to 2019 (four years). Results were compared with rainfall data, historical ground investigation records and monitoring surveys carried out at Ventnor to relate observations to geology, geomorphology and rainfall. Decomposition of InSAR viewing geometries to vertical and horizontal aligned well with previous ground-based studies. Subsidence of −9.8 mm a<sup>−1</sup> at the Lowtherville Graben and heave of +8.5 mm a<sup>−1</sup> along the coastline south of Ventnor Park were observed. Decomposition to east-west geometry results showed an eastward displacement of approximately 12.4 mm a<sup>−1</sup> along the coastline south of Ventnor Park, and a westward displacement of −3.7 mm a<sup>−1</sup> throughout built up sections of Ventnor town, indicating the landslide was displacing more in an eastern direction than vertically. The cause of this movement was investigated by using publicly available intrusive boreholes paired with Persistent Scatterer Interferometry, and a new ground model spanning east-west parallel to the coastline was presented. No evidence of significant ground movement was observed along heavily protected sections of the coastline, suggesting coastal defences comprised of concrete aprons and rip rap appear to be an effective coastal management/landslide stabilisation tool when compared to rip rap alone. The mechanism of this increased stability is likely due to the combination of toe weighting and reduced toe erosion. A lag of approximately 13–20 days was observed between high rainfall events and subsequent peaks in ground displacement, which was shorter than a 29 day lag observed in a previous study. Similar observations of prolonged rainfall resulting in prolonged displacements were also observed. The study demonstrates the capabilities of the PSI methodology in identifying the same ground movements that conventional methods provide. By providing detailed analysis of ground deformation of the Ventnor landslide, we demonstrate small ground movements, validated with existing ground movement surveys. Similar methodology can be applied to coastal landslides in urban environments worldwide, providing a relatively cheap and rapid resource for coastal landslide monitoring.
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spelling doaj.art-d14bf4aea3df499e9427b4d25948b1572023-11-22T15:07:12ZengMDPI AGRemote Sensing2072-42922021-09-011318371110.3390/rs13183711An Investigation into Ground Movement on the Ventnor Landslide Complex, UK Using Persistent Scatterer InterferometryWilliam O’Connor0Gosia Mider1James A. Lawrence2Stewart Agar3Philippa J. Mason4Richard Ghail5Jennifer Scoular6ByrneLooby Partners (Irl) Ltd., D12 VW27 Dublin, IrelandDepartment of Civil and Environmental Engineering, Imperial College London, London SW7 2AZ, UKDepartment of Civil and Environmental Engineering, Imperial College London, London SW7 2AZ, UKDepartment of Civil and Environmental Engineering, Imperial College London, London SW7 2AZ, UKDepartment of Earth Science and Engineering, Imperial College London, London SW7 2AZ, UKDepartment of Earth Sciences, Royal Holloway, University of London, Egham TW20 0EX, UKSkyGeo, Oude Delft 175, 2611 HB Delft, The NetherlandsAnalysis of ground movement rates along the coastline and upper sections of the Ventnor landslide complex was carried out utilizing Persistent Scatterer Interferometric Synthetic Aperture Radar methods using Sentinel-1 SAR data from 2015 to 2019 (four years). Results were compared with rainfall data, historical ground investigation records and monitoring surveys carried out at Ventnor to relate observations to geology, geomorphology and rainfall. Decomposition of InSAR viewing geometries to vertical and horizontal aligned well with previous ground-based studies. Subsidence of −9.8 mm a<sup>−1</sup> at the Lowtherville Graben and heave of +8.5 mm a<sup>−1</sup> along the coastline south of Ventnor Park were observed. Decomposition to east-west geometry results showed an eastward displacement of approximately 12.4 mm a<sup>−1</sup> along the coastline south of Ventnor Park, and a westward displacement of −3.7 mm a<sup>−1</sup> throughout built up sections of Ventnor town, indicating the landslide was displacing more in an eastern direction than vertically. The cause of this movement was investigated by using publicly available intrusive boreholes paired with Persistent Scatterer Interferometry, and a new ground model spanning east-west parallel to the coastline was presented. No evidence of significant ground movement was observed along heavily protected sections of the coastline, suggesting coastal defences comprised of concrete aprons and rip rap appear to be an effective coastal management/landslide stabilisation tool when compared to rip rap alone. The mechanism of this increased stability is likely due to the combination of toe weighting and reduced toe erosion. A lag of approximately 13–20 days was observed between high rainfall events and subsequent peaks in ground displacement, which was shorter than a 29 day lag observed in a previous study. Similar observations of prolonged rainfall resulting in prolonged displacements were also observed. The study demonstrates the capabilities of the PSI methodology in identifying the same ground movements that conventional methods provide. By providing detailed analysis of ground deformation of the Ventnor landslide, we demonstrate small ground movements, validated with existing ground movement surveys. Similar methodology can be applied to coastal landslides in urban environments worldwide, providing a relatively cheap and rapid resource for coastal landslide monitoring.https://www.mdpi.com/2072-4292/13/18/3711InSARcoastal monitoringpersistent scatterer interferometrylandslidesearth observationcoastal processes
spellingShingle William O’Connor
Gosia Mider
James A. Lawrence
Stewart Agar
Philippa J. Mason
Richard Ghail
Jennifer Scoular
An Investigation into Ground Movement on the Ventnor Landslide Complex, UK Using Persistent Scatterer Interferometry
Remote Sensing
InSAR
coastal monitoring
persistent scatterer interferometry
landslides
earth observation
coastal processes
title An Investigation into Ground Movement on the Ventnor Landslide Complex, UK Using Persistent Scatterer Interferometry
title_full An Investigation into Ground Movement on the Ventnor Landslide Complex, UK Using Persistent Scatterer Interferometry
title_fullStr An Investigation into Ground Movement on the Ventnor Landslide Complex, UK Using Persistent Scatterer Interferometry
title_full_unstemmed An Investigation into Ground Movement on the Ventnor Landslide Complex, UK Using Persistent Scatterer Interferometry
title_short An Investigation into Ground Movement on the Ventnor Landslide Complex, UK Using Persistent Scatterer Interferometry
title_sort investigation into ground movement on the ventnor landslide complex uk using persistent scatterer interferometry
topic InSAR
coastal monitoring
persistent scatterer interferometry
landslides
earth observation
coastal processes
url https://www.mdpi.com/2072-4292/13/18/3711
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