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Assessing debris flows using LIDAR differencing: 18 May 2005 Matata event, New Zealand

Assessing debris flows using LIDAR differencing: 18 May 2005 Matata event, New Zealand
Assessing debris flows using LIDAR differencing: 18 May 2005 Matata event, New Zealand
The town of Matata in the Eastern Bay of Plenty (New Zealand) experienced an extreme rainfall event on the 18 May 2005. This event triggered widespread landslips and large debris flows in the Awatarariki and Waitepuru catchments behind Matata. The Light Detection and Ranging technology (LIDAR) data sets flown prior to and following this event have been differenced and used in conjunction with a detailed field study to identify the distribution of debris and major sediment pathways which, from the Awatarariki catchment, transported at least 350,000 ± 50,000 m3 of debris. Debris flows were initially confined to stream valleys and controlled by the density and hydraulic thrust of the currents, before emerging onto the Awatarariki debris fan where a complex system of unconfined sediment pathways developed. Here, large boulders, clasts, logs and entire homes were deposited as the flows decelerated. Downstream from the debris fan, the pre-existing coastal foredune topography played a significant role in deflecting the more dilute currents that in filled lagoonal swale systems in both directions. The differenced LIDAR data have revealed several sectors characterised by significant variation in clast size, thickness and volume of debris as well as areas where post-debris flow cleanup and grading operations have resulted in man-made levees, sediment dumps, scoured channels and substantial graded areas. The application of differenced LIDAR data to a debris flow event demonstrates the techniques potential as a precise and powerful tool for hazard mapping and assessment.
lidar differencing, slope failure, debris flow, sediment pathways, matata, hazard assessment
0169-555X
75-84
Bull, J.M.
974037fd-544b-458f-98cc-ce8eca89e3c8
Miller, H.
ae9e9e7c-5fac-4031-a58a-bd71d74b36df
Gravley, D.M.
ee9abf6f-d9e3-4ec6-adf2-1c102752b7ec
Costello, D.
67577f3c-fbc2-4e62-8b88-64394c03aea7
Hikuroa, D.C.H.
3e82d4d6-b4c6-4086-be50-ca097c100054
Dix, J.K.
efbb0b6e-7dfd-47e1-ae96-92412bd45628
Bull, J.M.
974037fd-544b-458f-98cc-ce8eca89e3c8
Miller, H.
ae9e9e7c-5fac-4031-a58a-bd71d74b36df
Gravley, D.M.
ee9abf6f-d9e3-4ec6-adf2-1c102752b7ec
Costello, D.
67577f3c-fbc2-4e62-8b88-64394c03aea7
Hikuroa, D.C.H.
3e82d4d6-b4c6-4086-be50-ca097c100054
Dix, J.K.
efbb0b6e-7dfd-47e1-ae96-92412bd45628

Bull, J.M., Miller, H., Gravley, D.M., Costello, D., Hikuroa, D.C.H. and Dix, J.K. (2010) Assessing debris flows using LIDAR differencing: 18 May 2005 Matata event, New Zealand. Geomorphology, 124 (1-2), 75-84. (doi:10.1016/j.geomorph.2010.08.011).

Record type: Article

Abstract

The town of Matata in the Eastern Bay of Plenty (New Zealand) experienced an extreme rainfall event on the 18 May 2005. This event triggered widespread landslips and large debris flows in the Awatarariki and Waitepuru catchments behind Matata. The Light Detection and Ranging technology (LIDAR) data sets flown prior to and following this event have been differenced and used in conjunction with a detailed field study to identify the distribution of debris and major sediment pathways which, from the Awatarariki catchment, transported at least 350,000 ± 50,000 m3 of debris. Debris flows were initially confined to stream valleys and controlled by the density and hydraulic thrust of the currents, before emerging onto the Awatarariki debris fan where a complex system of unconfined sediment pathways developed. Here, large boulders, clasts, logs and entire homes were deposited as the flows decelerated. Downstream from the debris fan, the pre-existing coastal foredune topography played a significant role in deflecting the more dilute currents that in filled lagoonal swale systems in both directions. The differenced LIDAR data have revealed several sectors characterised by significant variation in clast size, thickness and volume of debris as well as areas where post-debris flow cleanup and grading operations have resulted in man-made levees, sediment dumps, scoured channels and substantial graded areas. The application of differenced LIDAR data to a debris flow event demonstrates the techniques potential as a precise and powerful tool for hazard mapping and assessment.

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e-pub ahead of print date: 26 August 2010
Published date: 1 December 2010
Keywords: lidar differencing, slope failure, debris flow, sediment pathways, matata, hazard assessment

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Local EPrints ID: 166613
URI: https://eprints.soton.ac.uk/id/eprint/166613
ISSN: 0169-555X
PURE UUID: 7e70da93-9382-4ed5-90ff-327038efaa2a

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Date deposited: 01 Nov 2010 09:41
Last modified: 18 Jul 2017 12:25

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Contributors

Author: J.M. Bull
Author: H. Miller
Author: D.M. Gravley
Author: D. Costello
Author: D.C.H. Hikuroa
Author: J.K. Dix

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