title: Nearshore and inner shelf sedimentation on the east Coromandel coast, New Zealand

authors: Bradshaw, Barry Edward

abstract: The east Coromandel coastline on the northeast coast of New Zealand has been characterised by localised erosion problems since its commercial subdivision. Increasing pressures have also arisen in recent years for possible use of the adjacent continental shelf as a repository for dredge and mining tailings, and extraction of commercial aggregate and mineral deposits. This has raised the question of dynamic links between the continental shelf and local beach systems I and resulting impacts on the coastline from such activities. The east Coromandel shelf study was therefore undertaken to investigate the modern and past shelf sedimentation processes, and relate these findings to local resource management issues. The results also contribute to the present international understanding of inner shelf sedimentation processes in 'storm-dominated' shelf environments.
Surficial sedimentation patterns have been examined by a variety of methods, including: the use of sea-bed drifters and Aanderaa current meters to determine the shelf hydrodynamics; the collection of 563 samples to determine surface sediment textural patterns; a detailed examination of morphological features on the sea floor through a series of 3 side-scan sonar surveys in which 620 km of sonograph and echosounding trace have been obtained; diver surveys using depth of activity rods to provide information on the mobility of surface sediments under different sea conditions; the collection, of 174 km of continuous sub-bottom seismic profiles which have been used to determine sub-surface stratigraphic patterns; and an examination of the provenance of shelf sediments through a detailed examination of their light and heavy mineralogy.
The east Coromandel coast is located on an active plate margin, resulting in the presence of a steep and rocky coastline fronted by a relatively narrow continental shelf (20 to 30 km wide), and a local geology dominated by Tertiary volcanics covered by a thin veneer of more recent volcanic air fall deposits. It is also located on a lee shelf in a mid-latitude zone of dominant westerly winds, with these prevailing weather patterns disrupted by high speed east to northeasterly winds associated with the infrequent passage of subtropical low pressure systems, occluded fronts, or more infrequent decaying tropical cyclones. This physiographic setting results in spatially and temporally highly variable sedimentation patterns, with sediment transport primarily controlled by the interaction of wave oscillatory and wind-generated currents during storm conditions. However, characteristics of tide-. and oceanic current-dominated conditions also occur in some areas. And conditions generally vary along the coast from being higher energy (current-dominated) on the southern exposed coast, to lower energy (wave- or current-dominated) on the northern embayed coastline. Shelf sedimentation is inferred to occur under three different scale events of fair weather, storm, and extreme storm conditions. The model proposed involves extreme storm conditions transporting large quantities of fine nearshore sands seawards onto the inner shelf surface, where they are slowly reworked along the shelf during annual storm events and back onshore during fair weather conditions. This latter onshore return of fine sands is proposed to result from an enhanced shear stress effect of long-period swell waves over coarse megarippled inner shelf sands.
Shelf sedimentation patterns within the study area are inferred to have been primarily established by processes occurring at about the time sea level stabitised 6500 years B.P. At this stage, transgressive shelf sediments were reworked into equilibrium with the regional oceanographic conditions by the winnowing of fine sand from coarser material during storms, with the fine sands subsequently transported onshore by wave-induced currents during calm periods. Depending on the volume of sediments incorporated into transgressive sand bodies and the local shelf gradients, each embayment then developed into either an integral part of the shelf transport system (usually off large estuary systems), with fine shelf sands moving onshore and forming wide barrier spits, or a closed sedimentary system unaffected by shelf sedimentation patterns (pocket embayments). Shelf equilibrium was evidently attained by the fine sands forming a steep seaward dipping concave-up nearshore profile, and coarse sands developing a flatter inner shelf profile.
An autochthonous mode of shelf sedimentation characterised the east Coromandel coast in early Holocene times, and is still evident under present conditions in most areas by the cyclical reworking of fine sands between the lower nearshore and inner shelf surfaces. Most east Coromandel embayments are, however, presently characterised by varying degrees of an allochthonous mode of shelf sedimentation. This involves the deposition of very fine grained, volcanic glass-enriched terrigenous sands, which are derived from either local catchments or Bay of Plenty river systems. The east Coromandel coast generally differs from most allochthonous shelf environments because the supply of terrigenous sediments has not as yet been sufficient to blanket the lower nearshore and inner shelf surfaces on the open ocean coastlines. Two separate modes of shelf sedimentation occur at present, with a nearshore inner shelf recycling of fine allochthonous shelf sands, and an open exchange of terrestrial autochthonous deposits from the upper nearshore surface to the mid shelf plain.
The results of the study suggest that coastal erosion problems can largely be resolved by establishing stable incipient and frontal dune systems along the coast. and encouraging accretion by renourishment from adjacent infilling harbour deposits. The study has also shown that the dispersion of dredged sediments provides potential benefits to the coast in terms of promoting beach accretion, and that sand and mineral extraction can proceed without adverse coastal erosion effects, provided the extraction does not interfere with the natural shelf sedimentation system.

text: Nearshore and inner shelf sedimentation on the east Coromandel coast, New Zealand The east Coromandel coastline on the northeast coast of New Zealand has been characterised by localised erosion problems since its commercial subdivision. Increasing pressures have also arisen in recent years for possible use of the adjacent continental shelf as a repository for dredge and mining tailings, and extraction of commercial aggregate and mineral deposits. This has raised the question of dynamic links between the continental shelf and local beach systems I and resulting impacts on the coastline from such activities. The east Coromandel shelf study was therefore undertaken to investigate the modern and past shelf sedimentation processes, and relate these findings to local resource management issues. The results also contribute to the present international understanding of inner shelf sedimentation processes in 'storm-dominated' shelf environments.
Surficial sedimentation patterns have been examined by a variety of methods, including: the use of sea-bed drifters and Aanderaa current meters to determine the shelf hydrodynamics; the collection of 563 samples to determine surface sediment textural patterns; a detailed examination of morphological features on the sea floor through a series of 3 side-scan sonar surveys in which 620 km of sonograph and echosounding trace have been obtained; diver surveys using depth of activity rods to provide information on the mobility of surface sediments under different sea conditions; the collection, of 174 km of continuous sub-bottom seismic profiles which have been used to determine sub-surface stratigraphic patterns; and an examination of the provenance of shelf sediments through a detailed examination of their light and heavy mineralogy.
The east Coromandel coast is located on an active plate margin, resulting in the presence of a steep and rocky coastline fronted by a relatively narrow continental shelf (20 to 30 km wide), and a local geology dominated by Tertiary volcanics covered by a thin veneer of more recent volcanic air fall deposits. It is also located on a lee shelf in a mid-latitude zone of dominant westerly winds, with these prevailing weather patterns disrupted by high speed east to northeasterly winds associated with the infrequent passage of subtropical low pressure systems, occluded fronts, or more infrequent decaying tropical cyclones. This physiographic setting results in spatially and temporally highly variable sedimentation patterns, with sediment transport primarily controlled by the interaction of wave oscillatory and wind-generated currents during storm conditions. However, characteristics of tide-. and oceanic current-dominated conditions also occur in some areas. And conditions generally vary along the coast from being higher energy (current-dominated) on the southern exposed coast, to lower energy (wave- or current-dominated) on the northern embayed coastline. Shelf sedimentation is inferred to occur under three different scale events of fair weather, storm, and extreme storm conditions. The model proposed involves extreme storm conditions transporting large quantities of fine nearshore sands seawards onto the inner shelf surface, where they are slowly reworked along the shelf during annual storm events and back onshore during fair weather conditions. This latter onshore return of fine sands is proposed to result from an enhanced shear stress effect of long-period swell waves over coarse megarippled inner shelf sands.
Shelf sedimentation patterns within the study area are inferred to have been primarily established by processes occurring at about the time sea level stabitised 6500 years B.P. At this stage, transgressive shelf sediments were reworked into equilibrium with the regional oceanographic conditions by the winnowing of fine sand from coarser material during storms, with the fine sands subsequently transported onshore by wave-induced currents during calm periods. Depending on the volume of sediments incorporated into transgressive sand bodies and the local shelf gradients, each embayment then developed into either an integral part of the shelf transport system (usually off large estuary systems), with fine shelf sands moving onshore and forming wide barrier spits, or a closed sedimentary system unaffected by shelf sedimentation patterns (pocket embayments). Shelf equilibrium was evidently attained by the fine sands forming a steep seaward dipping concave-up nearshore profile, and coarse sands developing a flatter inner shelf profile.
An autochthonous mode of shelf sedimentation characterised the east Coromandel coast in early Holocene times, and is still evident under present conditions in most areas by the cyclical reworking of fine sands between the lower nearshore and inner shelf surfaces. Most east Coromandel embayments are, however, presently characterised by varying degrees of an allochthonous mode of shelf sedimentation. This involves the deposition of very fine grained, volcanic glass-enriched terrigenous sands, which are derived from either local catchments or Bay of Plenty river systems. The east Coromandel coast generally differs from most allochthonous shelf environments because the supply of terrigenous sediments has not as yet been sufficient to blanket the lower nearshore and inner shelf surfaces on the open ocean coastlines. Two separate modes of shelf sedimentation occur at present, with a nearshore inner shelf recycling of fine allochthonous shelf sands, and an open exchange of terrestrial autochthonous deposits from the upper nearshore surface to the mid shelf plain.
The results of the study suggest that coastal erosion problems can largely be resolved by establishing stable incipient and frontal dune systems along the coast. and encouraging accretion by renourishment from adjacent infilling harbour deposits. The study has also shown that the dispersion of dredged sediments provides potential benefits to the coast in terms of promoting beach accretion, and that sand and mineral extraction can proceed without adverse coastal erosion effects, provided the extraction does not interfere with the natural shelf sedimentation system.

year: 1991

title: The ecology of community environmental groups: Integrating restoration, partnerships and citizen science

authors: Peters, Monica Annabel

subjects: conservation

abstract: New Zealand is facing a biodiversity crisis as forest and wetland habitat loss continue, and the quality of freshwater declines. But in recent years, a grassroots, nationwide network of community environmental groups has been expanding its contribution to restoring, protecting and enhancing these terrestrial and aquatic habitats. At the same time, government agencies are becoming increasingly reliant on voluntary community input to enhance conservation outcomes and to manage freshwater values. Globally, volunteer participation in environmental monitoring (citizen science) is recognised as an important mechanism for producing robust data that contributes to research, management and policy development, and for enhancing scientific and environmental literacy. New Zealand, however, lags far behind international efforts in acknowledging the value of, and uses for, the type of data that community groups undertaking environmental restoration may generate. Furthermore, strategies and policies around supporting community data generation as well as use have not yet been developed at a government level.  

This study sought to address this shortcoming by investigating characteristics of New Zealand community environmental groups and their projects, partnerships between groups and their project supporters, and the current and potential roles of environmental monitoring by these groups (i.e., citizen science). Data to inform this investigation was gathered using an online questionnaire sent to 540 community environmental groups across New Zealand, and 34 semi-structured interviews with project partners (e.g., resource managers and scientists),  including nine interviews with members of four well–established (>10 y) community environmental groups. Qualitative data from the questionnaire and interviews were analysed using inductive and deductive thematic analysis, and quantitative data from the questionnaire were analysed for frequency counts, chi-square significance and Random Forest modelling. 

Most groups surveyed were in existence for ≥ 6 y, small (up to 20 participants), and comprised older participants, aged 51-65 y. Groups reported focussing their restoration efforts on a variety of ecosystem types including forests (64%), streams (42%) and freshwater wetlands (33%), which were mostly situated on agency-owned or administered land (68%, n=290). Over two-thirds of groups combined environmental actions (particularly weed and pest control, and native tree planting), with advocacy and educational activities. The vast majority (93%, n=295) of groups relied on their project partners for support (e.g., site visits, funding and technical support), and reported a need for ongoing support in the future. Groups managing larger areas (≥ 8.1 ha), with medium to high partner support, and working on Department of Conservation or private land were more likely to be conducting their own monitoring. Their data were primarily used to support funding applications (63%; n=151), inform project restoration management, and share results with resource management agencies (both 60%; n=151), and for educational purposes (48%; n=157). Conducting water quality monitoring emerged as a strong area of interest for future work, though groups reported a lack of funding and people (both 45%; n=98), as well as technical skills (31%) as the largest challenges they faced for establishing new monitoring programmes generally. Project partners expressed concern over data quality and highlighted a lack of institutional systems for using community-generated data. 

This study provides insights into the methods used by groups to address environmental degradation in New Zealand and the contextual factors that shape their project activities. Enduring partnerships are critical, and more strategic approaches that are designed to support groups and their projects in the long-term are required. Both restoration and citizen science activities by groups are generally carried out independently of other groups, highlighting the need for improved networks between groups and with key agency project partners in order to: (1) achieve stronger conservation outcomes; (2) quantify restoration gains, and (3) improve the efficiency and efficacy of the limited resourcing available. At the same time, expectations of enhancing groups’ conservation and citizen science outputs must be balanced with the voluntary nature of community groups.

text: The ecology of community environmental groups: Integrating restoration, partnerships and citizen science New Zealand is facing a biodiversity crisis as forest and wetland habitat loss continue, and the quality of freshwater declines. But in recent years, a grassroots, nationwide network of community environmental groups has been expanding its contribution to restoring, protecting and enhancing these terrestrial and aquatic habitats. At the same time, government agencies are becoming increasingly reliant on voluntary community input to enhance conservation outcomes and to manage freshwater values. Globally, volunteer participation in environmental monitoring (citizen science) is recognised as an important mechanism for producing robust data that contributes to research, management and policy development, and for enhancing scientific and environmental literacy. New Zealand, however, lags far behind international efforts in acknowledging the value of, and uses for, the type of data that community groups undertaking environmental restoration may generate. Furthermore, strategies and policies around supporting community data generation as well as use have not yet been developed at a government level.  

This study sought to address this shortcoming by investigating characteristics of New Zealand community environmental groups and their projects, partnerships between groups and their project supporters, and the current and potential roles of environmental monitoring by these groups (i.e., citizen science). Data to inform this investigation was gathered using an online questionnaire sent to 540 community environmental groups across New Zealand, and 34 semi-structured interviews with project partners (e.g., resource managers and scientists),  including nine interviews with members of four well–established (>10 y) community environmental groups. Qualitative data from the questionnaire and interviews were analysed using inductive and deductive thematic analysis, and quantitative data from the questionnaire were analysed for frequency counts, chi-square significance and Random Forest modelling. 

Most groups surveyed were in existence for ≥ 6 y, small (up to 20 participants), and comprised older participants, aged 51-65 y. Groups reported focussing their restoration efforts on a variety of ecosystem types including forests (64%), streams (42%) and freshwater wetlands (33%), which were mostly situated on agency-owned or administered land (68%, n=290). Over two-thirds of groups combined environmental actions (particularly weed and pest control, and native tree planting), with advocacy and educational activities. The vast majority (93%, n=295) of groups relied on their project partners for support (e.g., site visits, funding and technical support), and reported a need for ongoing support in the future. Groups managing larger areas (≥ 8.1 ha), with medium to high partner support, and working on Department of Conservation or private land were more likely to be conducting their own monitoring. Their data were primarily used to support funding applications (63%; n=151), inform project restoration management, and share results with resource management agencies (both 60%; n=151), and for educational purposes (48%; n=157). Conducting water quality monitoring emerged as a strong area of interest for future work, though groups reported a lack of funding and people (both 45%; n=98), as well as technical skills (31%) as the largest challenges they faced for establishing new monitoring programmes generally. Project partners expressed concern over data quality and highlighted a lack of institutional systems for using community-generated data. 

This study provides insights into the methods used by groups to address environmental degradation in New Zealand and the contextual factors that shape their project activities. Enduring partnerships are critical, and more strategic approaches that are designed to support groups and their projects in the long-term are required. Both restoration and citizen science activities by groups are generally carried out independently of other groups, highlighting the need for improved networks between groups and with key agency project partners in order to: (1) achieve stronger conservation outcomes; (2) quantify restoration gains, and (3) improve the efficiency and efficacy of the limited resourcing available. At the same time, expectations of enhancing groups’ conservation and citizen science outputs must be balanced with the voluntary nature of community groups.

year: 2016

title: Moving away from home: Some social consequences for Tūhoe migrating to the Waikato

authors: Nikora, Linda Waimarie

subjects: psychology

abstract: To better understand the social consequences of migration away from traditional iwi regions, Tūhoe researchers intensively interviewed 40 Tūhoe people who had moved to the Waikato. It was found that most missed whanau and the community and made regular visits back home. Participants reported utilizing extensive whanau links to set themselves up in the Waikato, and many joined the Tūhoe associations in the Waikato. Others who did not join reported liking the idea that Tūhoe were there if needed. Some participants felt stronger in their Tūhoe identity since moving, and most reported noticing changes occurring in themselves or those back home over this period (they felt more worldly but saw those back home as more insular). While they did not interact much with tangata whenua, or participate in tangata whenua events, many said that they had a better appreciation of the local Tainui and the Kīngitanga groups since migrating. Finally, most would like to return to their iwi region for employment if it were available but saw little chance of this happening, and most reported wanting to retire there. The policy implications of both these points are explored.

text: Moving away from home: Some social consequences for Tūhoe migrating to the Waikato To better understand the social consequences of migration away from traditional iwi regions, Tūhoe researchers intensively interviewed 40 Tūhoe people who had moved to the Waikato. It was found that most missed whanau and the community and made regular visits back home. Participants reported utilizing extensive whanau links to set themselves up in the Waikato, and many joined the Tūhoe associations in the Waikato. Others who did not join reported liking the idea that Tūhoe were there if needed. Some participants felt stronger in their Tūhoe identity since moving, and most reported noticing changes occurring in themselves or those back home over this period (they felt more worldly but saw those back home as more insular). While they did not interact much with tangata whenua, or participate in tangata whenua events, many said that they had a better appreciation of the local Tainui and the Kīngitanga groups since migrating. Finally, most would like to return to their iwi region for employment if it were available but saw little chance of this happening, and most reported wanting to retire there. The policy implications of both these points are explored.

year: 2004