A New Technique for Measuring Runup Variation Using Sub-Aerial Video Imagery

Simple item page
dc.contributor.authorSalmon, Summer Anneen_NZ
dc.date.accessioned2008-03-03T10:09:51Z
dc.date.available2008-08-01T11:59:47Z
dc.date.issued2008en_NZ
dc.description.abstractVideo monitoring of beaches is becoming the preferred method for observing changes to nearshore morphology. Consequently this work investigates a new technique for predicting the probability of inundation that is based on measuring runup variation using video. Runup is defined as the water-level elevation maxima on the foreshore relative to the still water level and the waterline is defined as the position where the MWL intersects the beach face. Tairua, and Pauanui Beaches, on the north east coast of the North Island of New Zealand, were used as the field site in this study and represent two very different beaches with the same incoming wave and meteorological conditions. Tairua is most frequently in an intermediate beach state, whereas Pauanui is usually flatter in nature. In order to rectify runup observations, an estimate of the runup elevation was needed (Z). This was estimated by measuring the variation of the waterline over a tidal cycle from time-averaged video images during a storm event and provided beach morphology statistics (i.e. beach slope (α) and beach intercept (b)) used in the rectification process where Z=aX+b. The maximum swash excursions were digitized from time-stacks, and rectified to provide run-up timeseries with duration 20 minutes. Field calibrations revealed a videoed waterline that was seaward of the surveyed waterline. Quantification of this error gave a vertical offset of 0.33m at Tairua and 0.25m at Pauanui. At Tairua, incident wave energy was dominant in the swash zone, and the runup distributions followed a Rayleigh distribution. At Pauanui, the flatter beach, the runup distributions were approximately bimodal due to the dominance of infragravity energy in the swash signal. The slope of the beach was a major control on the runup elevation; runup at Pauanui was directly affected by the deepwater wave height and the tide, while at Tairua there was no correlation. Overall, the results of the study indicate realistic runup measurements, over a wide range of time scales and, importantly, during storm events. However, comparisons of videoed runup and empirical runup formulae revealed larger deviations as the beach steepness increased. Furthur tests need to be carried out to see if this is a limitation of this technique, used to measure runup. The runup statistics are consistently higher at Tairua and suggests that swash runs up higher on steeper beaches. However, because of the characteristics of flatter beaches (such as high water tables and low drainage efficiencies) the impact of extreme runup elevations on such beaches are more critical in regards to erosion and/ or inundation. The coastal environment is of great importance to Māori. Damage to the coast and coastal waahi tapu (places of spiritual importance) caused by erosion and inundation, adversely affects the spiritual and cultural well-being of Māori. For this reason, a chapter was dedicated to investigating the practices used by Māori to protect and preserve the coasts in accordance with tikanga Māori (Māori protocols). Mimicking nature was and still is a practice used by Māori to restore the beaches after erosive events, and includes replanting native dune plants and using natural materials on the beaches to stabilize the dunes. Tapu and rahui (the power and influence of the gods) were imposed on communities to prohibit and prevent people from free access to either food resources or to a particular place, in order to protect people and/ or resources. Interpretations of Māori oral histories provide insights into past local hazards and inform about the safety and viability of certain activities within an area. Environmental indicators were used to identify and forecast extreme weather conditions locally. Māori knowledge of past hazards, and the coastal environment as a whole, is a valuable resource and provides a unique source of expertise that can contribute to current coastal hazards management plans in New Zealand and provide insights about the areas that may again be impacted by natural hazards.en_NZ
dc.format.mimetypeapplication/pdf
dc.identifier.citationSalmon, S. A. (2008). A New Technique for Measuring Runup Variation Using Sub-Aerial Video Imagery (Thesis, Master of Science (MSc)). The University of Waikato, Hamilton, New Zealand. Retrieved from https://hdl.handle.net/10289/2511en
dc.identifier.urihttps://hdl.handle.net/10289/2511
dc.language.isoen
dc.publisherThe University of Waikatoen_NZ
dc.rightsAll items in Research Commons are provided for private study and research purposes and are protected by copyright with all rights reserved unless otherwise indicated.
dc.subjectWave Runupen_NZ
dc.subjectWaterline determinationen_NZ
dc.subjectSwash maximaen_NZ
dc.subjectProbability of Inundationen_NZ
dc.subjectinundationen_NZ
dc.subjecterosionen_NZ
dc.subjecttimestacksen_NZ
dc.subjectinfragravity wave energyen_NZ
dc.subjectextreme runup elevationen_NZ
dc.subjectCoastal Management and Maorien_NZ
dc.subjecttikanga Maorien_NZ
dc.titleA New Technique for Measuring Runup Variation Using Sub-Aerial Video Imageryen_NZ
dc.typeThesisen_NZ
pubs.place-of-publicationHamilton, New Zealanden_NZ
thesis.degree.disciplineEarth Sciencesen_NZ
thesis.degree.grantorUniversity of Waikatoen_NZ
thesis.degree.levelMasters
thesis.degree.nameMaster of Science (MSc)en_NZ
uow.date.accession2008-03-03T10:09:51Zen_NZ
uow.date.available2008-08-01T11:59:47Zen_NZ
uow.date.migrated2009-06-09T23:31:26Zen_NZ
uow.identifier.adthttp://adt.waikato.ac.nz/public/adt-uow20080303.100951en_NZ
Files
Original bundle
Now showing 1 - 1 of 1
Thumbnail Image
Name:
thesis.pdf
Size:
2.51 MB
Format:
Adobe Portable Document Format
Thumbnail Image
Name: thesis.pdf
Size: 2.51 MB
Kind: Adobe PDF
Collections
Masters Degree Theses