The morphodynamics of a sand and gravel barrier, Southern Hawke Bay, North Island, New Zealand
type: CreativeWork
description: Little is known about mixed sand and gravel beaches over an extended time period (seasons) or for specific wave energy events. This thesis addresses this problem by analysis of the gravel textures (sizes and forms) and the cross-shore transverse profiles for the southern Hawke Bay barrier, which possesses a well defined wave energy gradient and gravel supply and sink along some 16 km of coastline. Analysis of beach profile surveys show that the profile parameters (beach height, width, sediment volume and 'Profile Index') do not have normal distributions and can be highly skewed. The profile index parameter indicates the beachfaces are restricted to concave up and linear shapes. Consecutive cross shore profile surveys demonstrate the beachface has two response 'types' to high seas. Firstly, the beachface 'hinges' about MSL, shown by alternating maximum and minimum beach heights at the High and Low Water positions. So, when the High Water ridge is at a maximum height the Low Water platform is a minimum, and vice versa. The second response type occurs when an accretional High Water ridge welds onto an antecedent High Water ridge. At a seasonal time scale the updrift sites have an ongoing negative change of sediment volume (erosional). In addition, the profile index indicates a general evolution from concave up to a more linear profile shape (increasingly 'reflective'). These results suggest that as the profile shape evolves it does not affect the overall sediment loss (erosion). Over a season the winter gravel sizes are coarser, better sorted and coarse skewed compared to the summer season population. Generally, the sink gravels at the high-energy Marine Parade site are finer, more poorly sorted and more coarsely skewed than those at the low wave energy Clifton gravel supply. Indeed, at the sink the high water moderate wave energy (breaking wave height Hb > 1.0 m; breaking wave steepness Bs > 0.03) gravels depositional at the High Water ridge show increasing coarse ske…
abstract: Little is known about mixed sand and gravel beaches over an extended time period (seasons) or for specific wave energy events. This thesis addresses this problem by analysis of the gravel textures (sizes and forms) and the cross-shore transverse profiles for the southern Hawke Bay barrier, which possesses a well defined wave energy gradient and gravel supply and sink along some 16 km of coastline. Analysis of beach profile surveys show that the profile parameters (beach height, width, sediment volume and 'Profile Index') do not have normal distributions and can be highly skewed. The profile index parameter indicates the beachfaces are restricted to concave up and linear shapes. Consecutive cross shore profile surveys demonstrate the beachface has two response 'types' to high seas. Firstly, the beachface 'hinges' about MSL, shown by alternating maximum and minimum beach heights at the High and Low Water positions. So, when the High Water ridge is at a maximum height the Low Water platform is a minimum, and vice versa. The second response type occurs when an accretional High Water ridge welds onto an antecedent High Water ridge. At a seasonal time scale the updrift sites have an ongoing negative change of sediment volume (erosional). In addition, the profile index indicates a general evolution from concave up to a more linear profile shape (increasingly 'reflective'). These results suggest that as the profile shape evolves it does not affect the overall sediment loss (erosion). Over a season the winter gravel sizes are coarser, better sorted and coarse skewed compared to the summer season population. Generally, the sink gravels at the high-energy Marine Parade site are finer, more poorly sorted and more coarsely skewed than those at the low wave energy Clifton gravel supply. Indeed, at the sink the high water moderate wave energy (breaking wave height Hb > 1.0 m; breaking wave steepness Bs > 0.03) gravels depositional at the High Water ridge show increasing coarse ske…
author: White, John L.
license: https://researchcommons.waikato.ac.nz/bitstreams/26e676ce-5ff2-4c9a-bd1d-fc0967cf9634/download
date published: 2005
date modified: 2026-07-24T05:57:15Z
provider: University Waikato
publisher: Networked Digital Library of Theses and Dissertations
type: WebPage
source organization: The University of Waikato