{"id":{"repo_id":"auckland-ms","oai_identifier":"oai:researchspace.auckland.ac.nz:2292/67530"},"canonical_url":"https://search.dev.ndltd.org/etd/auckland-ms/oai:researchspace.auckland.ac.nz:2292/67530","repository":{"repo_id":"auckland-ms","name":"University of Auckland","base_url":"https://researchspace.auckland.ac.nz/server/oai/request"},"display":{"title":"Delineation of Landslide Hazard and Development of Mitigation Tools in a Vulnerable City","abstract":"Landslides are widespread geomorphological features on the North Island of New Zealand, where they represent one of the primary landscape-forming processes. Indeed, the East Coast region has some of the highest erosion rates in the world, due to its proximity to an active plate boundary, susceptibility to high-intensity storms, and steep terrain underlain by young, soft sedimentary rocks and soils. In the city of Gisborne, the expansion of residential blocks into steeper terrain in peri-urban areas has required improved capacity for the characterization and monitoring of slope stability. Landslides have affected several properties and destroyed infrastructure. Slope failure commonly occurs during heavy rainfall events when slow-moving retrogressive slides transition into earthflows and mudflows. In this study, in-situ sampling, field surveys and laboratory testing combined with remote sensing techniques were used to report on emerging slope instability hazards and understand landslide pre- and post-failure behaviour in Gisborne. Retrogressive failure of the Wallis Road (Chapter 4) and Richardson Avenue (Chapter 5) landslides are ongoing and have already led to the abandonment of homes. The Wallis Road landslide has been particularly active since mid-2017, with the headscarp area sliding into a constrained mudflow downslope, which then descends a cliff before terminating on the beach. Similarly, at the Richardson Avenue landslide, Sentinel-1 InSAR analysis determined that gradual deformation began in 2017 following two ex-tropical cyclone events. The deformation downslope continued until an initial failure in July 2020. Subsequent to that event, some parts of the slope accelerated, leading to a further reactivation event in November 2021, following heavy rainfall. During the November 2021 event, average line of sight (LOS) velocities ranged from -7.9 mm/yr to −11.2 mm/yr, and deformation rates in the vertical direction (related to rotational sliding) averaged −11.2 mm/yr to −11.9 mm/yr, consistent with field observations. While activity at both landslides appears to be linked to rainfall-induced increases in soil moisture, this is due to the effects of prolonged periods of rainfall, rather than the passage of high-intensity cyclonic storms. Finally, based on observation data from Sentinel-1 imagery, this study uses InSAR to reveal the distribution of deformation across Gisborne's steepland periphery from January 2016 to December 2021 (Chapter 6). The results were combined with a regional LiDAR dataset, aerial imagery and field observations to delineate areas of slope deformation. Slope deformation time series data were compared with rainfall records and also identified seasonal changes due to shrink- swell of expansive soils. Although the InSAR displacement data contains some noise, results identified 132 unstable slopes within the study area caused by soil creep and earthflows. Also, the shrink-swell of expansive soils causes a seasonal pattern of displacements, which varied by 10-20 mm/yr between Austral winter and summer, strongly related to rainfall, of potential importance for utilities and infrastructure.","abstract_html":"Landslides are widespread geomorphological features on the North Island of New Zealand, where they represent one of the primary landscape-forming processes. Indeed, the East Coast region has some of the highest erosion rates in the world, due to its proximity to an active plate boundary, susceptibility to high-intensity storms, and steep terrain underlain by young, soft sedimentary rocks and soils. In the city of Gisborne, the expansion of residential blocks into steeper terrain in peri-urban areas has required improved capacity for the characterization and monitoring of slope stability. Landslides have affected several properties and destroyed infrastructure. Slope failure commonly occurs during heavy rainfall events when slow-moving retrogressive slides transition into earthflows and mudflows. In this study, in-situ sampling, field surveys and laboratory testing combined with remote sensing techniques were used to report on emerging slope instability hazards and understand landslide pre- and post-failure behaviour in Gisborne. Retrogressive failure of the Wallis Road (Chapter 4) and Richardson Avenue (Chapter 5) landslides are ongoing and have already led to the abandonment of homes. The Wallis Road landslide has been particularly active since mid-2017, with the headscarp area sliding into a constrained mudflow downslope, which then descends a cliff before terminating on the beach. Similarly, at the Richardson Avenue landslide, Sentinel-1 InSAR analysis determined that gradual deformation began in 2017 following two ex-tropical cyclone events. The deformation downslope continued until an initial failure in July 2020. Subsequent to that event, some parts of the slope accelerated, leading to a further reactivation event in November 2021, following heavy rainfall. During the November 2021 event, average line of sight (LOS) velocities ranged from -7.9 mm/yr to −11.2 mm/yr, and deformation rates in the vertical direction (related to rotational sliding) averaged −11.2 mm/yr to −11.9 mm/yr, consistent with field observations. While activity at both landslides appears to be linked to rainfall-induced increases in soil moisture, this is due to the effects of prolonged periods of rainfall, rather than the passage of high-intensity cyclonic storms. Finally, based on observation data from Sentinel-1 imagery, this study uses InSAR to reveal the distribution of deformation across Gisborne's steepland periphery from January 2016 to December 2021 (Chapter 6). The results were combined with a regional LiDAR dataset, aerial imagery and field observations to delineate areas of slope deformation. Slope deformation time series data were compared with rainfall records and also identified seasonal changes due to shrink- swell of expansive soils. Although the InSAR displacement data contains some noise, results identified 132 unstable slopes within the study area caused by soil creep and earthflows. Also, the shrink-swell of expansive soils causes a seasonal pattern of displacements, which varied by 10-20 mm/yr between Austral winter and summer, strongly related to rainfall, of potential importance for utilities and infrastructure.","abstract_has_math":false,"creators":["Cook, Matt E."],"institution":"ResearchSpace@Auckland","degree_name":"PhD","degree_level":"Doctoral","degree_discipline":"Geology","degree_department":null,"school":null,"contributors":[],"advisors":["Brook, Martin","Tunnicliffe, Jon"],"committee_chairs":[],"committee_members":[],"year":2024,"date_issued":"2024","date_published":"2024","updated_at":"2026-07-24T01:03:56Z","subjects":[],"languages":[],"rights":["Items in ResearchSpace are protected by copyright, with all rights reserved, unless otherwise indicated."],"rights_urls":["https://researchspace.auckland.ac.nz/docs/uoa-docs/rights.htm"],"identifier_entries":[]},"links":{"outbound_url":"https://hdl.handle.net/2292/67530","outbound_label":"Handle","outbound_source":"dc:identifier.uri"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:contributor.advisor","label":"Advisor","values":["Brook, Martin","Tunnicliffe, Jon"]},{"key":"dc:creator","label":"Author","values":["Cook, Matt E."]}]},{"id":"academic_context","label":"Academic Context","entries":[{"key":"dc:date.accessioned","label":"Dc Date Accessioned","values":["2024-02-28T18:57:05Z"]},{"key":"dc:date.available","label":"Dc Date Available","values":["2024-02-28T18:57:05Z"]},{"key":"dc:date.issued","label":"Date","values":["2024"]},{"key":"dc:publisher","label":"Institution","values":["ResearchSpace@Auckland"]},{"key":"dc:type","label":"Dc Type","values":["Thesis"]},{"key":"thesis:degree_discipline","label":"Discipline","values":["Geology"]},{"key":"thesis:degree_level","label":"Degree Level","values":["Doctoral"]},{"key":"thesis:degree_name","label":"Degree Name","values":["PhD"]},{"key":"thesis:institution_name","label":"Thesis Institution Name","values":["The University of Auckland"]}]},{"id":"language_rights","label":"Language and Rights","entries":[{"key":"dc:rights","label":"Dc Rights","values":["Items in ResearchSpace are protected by copyright, with all rights reserved, unless otherwise indicated."]},{"key":"dc:rights.uri","label":"Rights URI","values":["https://researchspace.auckland.ac.nz/docs/uoa-docs/rights.htm"]}]},{"id":"identifiers","label":"Identifiers","entries":[{"key":"dc:identifier.uri","label":"Identifier URI","values":["https://hdl.handle.net/2292/67530"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description.abstract","label":"Abstract","values":["Landslides are widespread geomorphological features on the North Island of New Zealand, where they represent one of the primary landscape-forming processes. Indeed, the East Coast region has some of the highest erosion rates in the world, due to its proximity to an active plate boundary, susceptibility to high-intensity storms, and steep terrain underlain by young, soft sedimentary rocks and soils. In the city of Gisborne, the expansion of residential blocks into steeper terrain in peri-urban areas has required improved capacity for the characterization and monitoring of slope stability. Landslides have affected several properties and destroyed infrastructure. Slope failure commonly occurs during heavy rainfall events when slow-moving retrogressive slides transition into earthflows and mudflows. In this study, in-situ sampling, field surveys and laboratory testing combined with remote sensing techniques were used to report on emerging slope instability hazards and understand landslide pre- and post-failure behaviour in Gisborne. Retrogressive failure of the Wallis Road (Chapter 4) and Richardson Avenue (Chapter 5) landslides are ongoing and have already led to the abandonment of homes. The Wallis Road landslide has been particularly active since mid-2017, with the headscarp area sliding into a constrained mudflow downslope, which then descends a cliff before terminating on the beach. Similarly, at the Richardson Avenue landslide, Sentinel-1 InSAR analysis determined that gradual deformation began in 2017 following two ex-tropical cyclone events. The deformation downslope continued until an initial failure in July 2020. Subsequent to that event, some parts of the slope accelerated, leading to a further reactivation event in November 2021, following heavy rainfall. During the November 2021 event, average line of sight (LOS) velocities ranged from -7.9 mm/yr to −11.2 mm/yr, and deformation rates in the vertical direction (related to rotational sliding) averaged −11.2 mm/yr to −11.9 mm/yr, consistent with field observations. While activity at both landslides appears to be linked to rainfall-induced increases in soil moisture, this is due to the effects of prolonged periods of rainfall, rather than the passage of high-intensity cyclonic storms. Finally, based on observation data from Sentinel-1 imagery, this study uses InSAR to reveal the distribution of deformation across Gisborne's steepland periphery from January 2016 to December 2021 (Chapter 6). The results were combined with a regional LiDAR dataset, aerial imagery and field observations to delineate areas of slope deformation. Slope deformation time series data were compared with rainfall records and also identified seasonal changes due to shrink- swell of expansive soils. Although the InSAR displacement data contains some noise, results identified 132 unstable slopes within the study area caused by soil creep and earthflows. Also, the shrink-swell of expansive soils causes a seasonal pattern of displacements, which varied by 10-20 mm/yr between Austral winter and summer, strongly related to rainfall, of potential importance for utilities and infrastructure."]},{"key":"dc:title","label":"Title","values":["Delineation of Landslide Hazard and Development of Mitigation Tools in a Vulnerable City"]}]}],"canonical_facts":{"dc:contributor.advisor":["Brook, Martin","Tunnicliffe, Jon"],"dc:creator":["Cook, Matt E."],"dc:date.accessioned":["2024-02-28T18:57:05Z"],"dc:date.available":["2024-02-28T18:57:05Z"],"dc:date.issued":["2024"],"dc:description.abstract":["Landslides are widespread geomorphological features on the North Island of New Zealand, where they represent one of the primary landscape-forming processes. Indeed, the East Coast region has some of the highest erosion rates in the world, due to its proximity to an active plate boundary, susceptibility to high-intensity storms, and steep terrain underlain by young, soft sedimentary rocks and soils. In the city of Gisborne, the expansion of residential blocks into steeper terrain in peri-urban areas has required improved capacity for the characterization and monitoring of slope stability. Landslides have affected several properties and destroyed infrastructure. Slope failure commonly occurs during heavy rainfall events when slow-moving retrogressive slides transition into earthflows and mudflows. In this study, in-situ sampling, field surveys and laboratory testing combined with remote sensing techniques were used to report on emerging slope instability hazards and understand landslide pre- and post-failure behaviour in Gisborne. Retrogressive failure of the Wallis Road (Chapter 4) and Richardson Avenue (Chapter 5) landslides are ongoing and have already led to the abandonment of homes. The Wallis Road landslide has been particularly active since mid-2017, with the headscarp area sliding into a constrained mudflow downslope, which then descends a cliff before terminating on the beach. Similarly, at the Richardson Avenue landslide, Sentinel-1 InSAR analysis determined that gradual deformation began in 2017 following two ex-tropical cyclone events. The deformation downslope continued until an initial failure in July 2020. Subsequent to that event, some parts of the slope accelerated, leading to a further reactivation event in November 2021, following heavy rainfall. During the November 2021 event, average line of sight (LOS) velocities ranged from -7.9 mm/yr to −11.2 mm/yr, and deformation rates in the vertical direction (related to rotational sliding) averaged −11.2 mm/yr to −11.9 mm/yr, consistent with field observations. While activity at both landslides appears to be linked to rainfall-induced increases in soil moisture, this is due to the effects of prolonged periods of rainfall, rather than the passage of high-intensity cyclonic storms. Finally, based on observation data from Sentinel-1 imagery, this study uses InSAR to reveal the distribution of deformation across Gisborne's steepland periphery from January 2016 to December 2021 (Chapter 6). The results were combined with a regional LiDAR dataset, aerial imagery and field observations to delineate areas of slope deformation. Slope deformation time series data were compared with rainfall records and also identified seasonal changes due to shrink- swell of expansive soils. Although the InSAR displacement data contains some noise, results identified 132 unstable slopes within the study area caused by soil creep and earthflows. Also, the shrink-swell of expansive soils causes a seasonal pattern of displacements, which varied by 10-20 mm/yr between Austral winter and summer, strongly related to rainfall, of potential importance for utilities and infrastructure."],"dc:identifier.uri":["https://hdl.handle.net/2292/67530"],"dc:publisher":["ResearchSpace@Auckland"],"dc:rights":["Items in ResearchSpace are protected by copyright, with all rights reserved, unless otherwise indicated."],"dc:rights.uri":["https://researchspace.auckland.ac.nz/docs/uoa-docs/rights.htm"],"dc:title":["Delineation of Landslide Hazard and Development of Mitigation Tools in a Vulnerable City"],"dc:type":["Thesis"],"thesis:degree_discipline":["Geology"],"thesis:degree_level":["Doctoral"],"thesis:degree_name":["PhD"],"thesis:institution_name":["The University of Auckland"]},"updated_at":"2026-07-24T01:03:56Z"}