title: Stream sediment sources: A comparison between a native forest catchment and a mixed-use pine and pasture catchment in the Waikato Region of New Zealand

authors: Huirama, Manawa Kokiri

subjects: sediment

abstract: Sediment entering streams and rivers is a global concern for water quality. Suspended sediment can reduce visual clarity, light penetration, and amenity values of water. Transported sediment can also smother benthic fauna and flora and increase the infilling of receiving environments such as lakes and estuaries. In New Zealand catchments, there are three primary sources of erosion i) hillslopes through sheetwash and rill erosion ii) stream bank erosion and iii) mass wasting of hillslopes. There has been little research conducted on the relative contribution of sediment sources to fine sediment within New Zealand. However, some limited research in New Zealand, and research from other countries has identified stream bank erosion as a major source of fine sediment.  

The aim of this thesis was to identify the contribution of various erosion sources to sediment in streams. This study tested the hypothesis that stream bank erosion would be dominant in a pasture catchment, and hillslope erosion would be dominant in a native catchment. This study used paired, adjacent headwater catchments with similar sizes, slopes, soils, and underlying geology but contrasting land uses. The Mangaotama catchment was predominantly pastoral land use, with some areas of pine plantation, while the Whakakai catchment had regenerated and pristine indigenous forest. 

Qualitative field surveys were conducted in the Mangaotama catchment (total length 1.3 km with 0.9 km under pastoral land use and 0.4 km under pine plantation) and Whakakai catchment (0.9 km) to assess stream and riparian conditions including stream bank erosion. Stream banks in the Mangaotama catchment were primarily stable (pasture section (left: 64%, right: 65%); pine section (left: 91%, right: 85%)) and the Whakakai catchment was generally stable (left: 84%, right: 86%). Stock damage dominated stream bank erosion in the pastoral section of the Mangaotama catchment (left: 23%, right: 19%), while stream bank undercutting dominated the pine section of the Mangaotama (left: 9%, right: 13%) and the Whakakai catchment (left: 15% and right: 13%). 

Sediment fingerprinting used radionuclides (¹³⁷Cs, ²¹⁰Pbₑₓ, ²²⁶Ra and ²²⁸Ra), to determine the relative contribution of stream bank erosion and hillslope erosion in suspended sediment samples collected during high flow events. The concentrations of all radionuclides were higher in the hillslopes (P <0.001) ((mean ¹³⁷Cs: 5.8 Bq kg⁻¹, std: 2.4 Bq kg⁻¹); (mean ²¹⁰Pbex: 32.5 Bq kg⁻¹, std: 16.0 Bq kg⁻¹); (mean ²²⁶Ra: 24.9 Bq kg⁻¹, std: 2.1 Bq kg⁻¹); (mean ²²⁸Ra: 35.3 Bq kg⁻¹, std: 4.0 Bq kg⁻¹)) of both the Mangaotama and Whakakai catchments than in the streambanks ((mean ¹³⁷Cs: 0.9 Bq kg⁻¹, std: 0.3 Bq kg⁻¹); (mean ²¹⁰Pbex: 8.4 Bq kg-1, std: 4.6 Bq kg⁻¹); (mean ²²⁶Ra: 28.8 Bq kg⁻¹, std: 1.7 Bq kg⁻¹); (mean ²²⁸Ra: 47.2 Bq kg⁻¹, std: 2.2 Bq kg⁻¹)), clearly distinguishing the sources of sediment. A numerical mixing model determined that stream bank erosion was the dominant source of sediment (90%) within both catchments, with the remaining 10% originating from hillslope erosion. 

Simultaneously recorded continuous turbidity and discharge (Q) data were analysed for the previous year (2017). Six flood events were analysed in the Mangaotama and Whakakai catchments (three large events Q > 1,000 l s⁻¹ and three smaller events (Mangaotama: Q between 127 l s⁻¹ to 606 l s⁻¹, Whakakai: Q between 219 l s⁻¹ and 1398 l s⁻¹). Turbidity was greater in the Mangaotama catchment for four events (ranging from 237 NTU to 3,402 NTU) and greater in the Whakakai catchment for two events (1,293 NTU and 1,435 NTU). Strong clockwise hysteresis dominated (5 out of 6) of the flood events in the Mangaotama catchment, suggesting that stream bank erosion was the dominant source of sediment. Weak anti-clockwise hysteresis dominated the Whakakai catchment (5 out of 6) flood events, indicating sources further away from the sample point. Anti-clockwise hysteresis is primarily associated with hillslope erosion, however, in this study, it was most likely attributed to stream bank erosion sources in the upper reaches of the Whakakai catchment. 

Terrestrial photogrammetry was tested, as it is potentially an effective, simple and cost-effective tool to monitor stream bank erosion over time. Further, a baseline was established which could be re-surveyed though it is recommended that further baseline sites be established to provide improved rigour.

Stream bank erosion was the greatest contributor (90%) to stream sediment loads in both the Mangaotama and Whakakai catchments, with the remaining 10% the stream sediment in both catchments being derived from hillslope erosion. Thus, the hypothesis for this study was rejected. This study demonstrates that stream bank erosion is a natural process and can dominate the supply of sediment to river systems even in relatively unimpacted catchments. Catchment managers need to take this into account when considering catchment rehabilitation projects aimed at reducing the delivery of sediment to streams.

text: Stream sediment sources: A comparison between a native forest catchment and a mixed-use pine and pasture catchment in the Waikato Region of New Zealand Sediment entering streams and rivers is a global concern for water quality. Suspended sediment can reduce visual clarity, light penetration, and amenity values of water. Transported sediment can also smother benthic fauna and flora and increase the infilling of receiving environments such as lakes and estuaries. In New Zealand catchments, there are three primary sources of erosion i) hillslopes through sheetwash and rill erosion ii) stream bank erosion and iii) mass wasting of hillslopes. There has been little research conducted on the relative contribution of sediment sources to fine sediment within New Zealand. However, some limited research in New Zealand, and research from other countries has identified stream bank erosion as a major source of fine sediment.  

The aim of this thesis was to identify the contribution of various erosion sources to sediment in streams. This study tested the hypothesis that stream bank erosion would be dominant in a pasture catchment, and hillslope erosion would be dominant in a native catchment. This study used paired, adjacent headwater catchments with similar sizes, slopes, soils, and underlying geology but contrasting land uses. The Mangaotama catchment was predominantly pastoral land use, with some areas of pine plantation, while the Whakakai catchment had regenerated and pristine indigenous forest. 

Qualitative field surveys were conducted in the Mangaotama catchment (total length 1.3 km with 0.9 km under pastoral land use and 0.4 km under pine plantation) and Whakakai catchment (0.9 km) to assess stream and riparian conditions including stream bank erosion. Stream banks in the Mangaotama catchment were primarily stable (pasture section (left: 64%, right: 65%); pine section (left: 91%, right: 85%)) and the Whakakai catchment was generally stable (left: 84%, right: 86%). Stock damage dominated stream bank erosion in the pastoral section of the Mangaotama catchment (left: 23%, right: 19%), while stream bank undercutting dominated the pine section of the Mangaotama (left: 9%, right: 13%) and the Whakakai catchment (left: 15% and right: 13%). 

Sediment fingerprinting used radionuclides (¹³⁷Cs, ²¹⁰Pbₑₓ, ²²⁶Ra and ²²⁸Ra), to determine the relative contribution of stream bank erosion and hillslope erosion in suspended sediment samples collected during high flow events. The concentrations of all radionuclides were higher in the hillslopes (P <0.001) ((mean ¹³⁷Cs: 5.8 Bq kg⁻¹, std: 2.4 Bq kg⁻¹); (mean ²¹⁰Pbex: 32.5 Bq kg⁻¹, std: 16.0 Bq kg⁻¹); (mean ²²⁶Ra: 24.9 Bq kg⁻¹, std: 2.1 Bq kg⁻¹); (mean ²²⁸Ra: 35.3 Bq kg⁻¹, std: 4.0 Bq kg⁻¹)) of both the Mangaotama and Whakakai catchments than in the streambanks ((mean ¹³⁷Cs: 0.9 Bq kg⁻¹, std: 0.3 Bq kg⁻¹); (mean ²¹⁰Pbex: 8.4 Bq kg-1, std: 4.6 Bq kg⁻¹); (mean ²²⁶Ra: 28.8 Bq kg⁻¹, std: 1.7 Bq kg⁻¹); (mean ²²⁸Ra: 47.2 Bq kg⁻¹, std: 2.2 Bq kg⁻¹)), clearly distinguishing the sources of sediment. A numerical mixing model determined that stream bank erosion was the dominant source of sediment (90%) within both catchments, with the remaining 10% originating from hillslope erosion. 

Simultaneously recorded continuous turbidity and discharge (Q) data were analysed for the previous year (2017). Six flood events were analysed in the Mangaotama and Whakakai catchments (three large events Q > 1,000 l s⁻¹ and three smaller events (Mangaotama: Q between 127 l s⁻¹ to 606 l s⁻¹, Whakakai: Q between 219 l s⁻¹ and 1398 l s⁻¹). Turbidity was greater in the Mangaotama catchment for four events (ranging from 237 NTU to 3,402 NTU) and greater in the Whakakai catchment for two events (1,293 NTU and 1,435 NTU). Strong clockwise hysteresis dominated (5 out of 6) of the flood events in the Mangaotama catchment, suggesting that stream bank erosion was the dominant source of sediment. Weak anti-clockwise hysteresis dominated the Whakakai catchment (5 out of 6) flood events, indicating sources further away from the sample point. Anti-clockwise hysteresis is primarily associated with hillslope erosion, however, in this study, it was most likely attributed to stream bank erosion sources in the upper reaches of the Whakakai catchment. 

Terrestrial photogrammetry was tested, as it is potentially an effective, simple and cost-effective tool to monitor stream bank erosion over time. Further, a baseline was established which could be re-surveyed though it is recommended that further baseline sites be established to provide improved rigour.

Stream bank erosion was the greatest contributor (90%) to stream sediment loads in both the Mangaotama and Whakakai catchments, with the remaining 10% the stream sediment in both catchments being derived from hillslope erosion. Thus, the hypothesis for this study was rejected. This study demonstrates that stream bank erosion is a natural process and can dominate the supply of sediment to river systems even in relatively unimpacted catchments. Catchment managers need to take this into account when considering catchment rehabilitation projects aimed at reducing the delivery of sediment to streams.

year: 2019

title: Intelligent participation: communicating knowledge in cross-functional project teams

authors: Jones, Rachel Anne

subjects: communication

abstract: This paper suggests 'intelligent participation' as a framework through which members of cross-functional project teams can engage productively in communicating knowledge. It identifies the transmission model of communication, and its accompanying discourse, as an implicit, but restrictive, conceptualisation underpinning much current research. It critiques that model as an oversimplification of energetic team exchanges into inert information transfer and proposes instead that communication be understood as a complex, living process. Understanding communicating knowledge as an ongoing series of interactions among participants, this paper fuses complex responsive process theory with the perspective of complex adaptive systems. It argues that focusing on local interactions within a systemic context enables a more realistic account of project interactions. This approach augments project management work on knowledge transfer with current communication theories, and also suggests specific capacities that may be developed to integrate cross-functional conversations that foster innovative, emergent outcomes.

text: Intelligent participation: communicating knowledge in cross-functional project teams This paper suggests 'intelligent participation' as a framework through which members of cross-functional project teams can engage productively in communicating knowledge. It identifies the transmission model of communication, and its accompanying discourse, as an implicit, but restrictive, conceptualisation underpinning much current research. It critiques that model as an oversimplification of energetic team exchanges into inert information transfer and proposes instead that communication be understood as a complex, living process. Understanding communicating knowledge as an ongoing series of interactions among participants, this paper fuses complex responsive process theory with the perspective of complex adaptive systems. It argues that focusing on local interactions within a systemic context enables a more realistic account of project interactions. This approach augments project management work on knowledge transfer with current communication theories, and also suggests specific capacities that may be developed to integrate cross-functional conversations that foster innovative, emergent outcomes.

year: 2009

title: A case study of Pipiri Ki A Papatūānuku

authors: Tamoko-o-te-rangi, Ormsby

subjects: environmental initiatives

abstract: This thesis is an examination and analysis of the environmental initiative Pipiri Ki A Papatūānuku, co-founded by Waimirirangi Ormsby (née Koopu-Stone) and myself, Tamoko Ormsby. The primary aim of this research was to achieve an understanding of the PKP initiative at the individual level and to inform future collective action at the community level. As such, my primary research question is:

How can Pipiri Ki A Papatūānuku inform community-scale action that contributes to our more-than-human relationship with Papatūānuku within our current capitalist settler-colonial context?

The study is part-autoethnographic in that it is informed by my personal reflections and experiences as a co-founder, operator, and participant of the initiative. In addition, the study explores the number of participants who signed up yearly for each action and employs a brief descriptive analysis of the initiative.

The literature review explores how common Western notions of environmentalism are devoid of the spiritual, cultural, and relational aspects present within indigenous and Māori knowledge systems. It touches on the histories of capitalism and colonialism and how these have led to the consumptogenic society we are in. It aims to illustrate the nexus between the Māori and Western Eurocentric worlds.

He Whatu is the framework that has emerged from this case study as the means to respond to the primary research question. The framework was developed by analyzing the key themes of PKP over the years 2017 to 2021. He Whatu has five key elements: Identity, Language, Distance, Practicality, and Influence; each with three subcategories. It is activated through provoking key conversations to inform future community action.

text: A case study of Pipiri Ki A Papatūānuku This thesis is an examination and analysis of the environmental initiative Pipiri Ki A Papatūānuku, co-founded by Waimirirangi Ormsby (née Koopu-Stone) and myself, Tamoko Ormsby. The primary aim of this research was to achieve an understanding of the PKP initiative at the individual level and to inform future collective action at the community level. As such, my primary research question is:

How can Pipiri Ki A Papatūānuku inform community-scale action that contributes to our more-than-human relationship with Papatūānuku within our current capitalist settler-colonial context?

The study is part-autoethnographic in that it is informed by my personal reflections and experiences as a co-founder, operator, and participant of the initiative. In addition, the study explores the number of participants who signed up yearly for each action and employs a brief descriptive analysis of the initiative.

The literature review explores how common Western notions of environmentalism are devoid of the spiritual, cultural, and relational aspects present within indigenous and Māori knowledge systems. It touches on the histories of capitalism and colonialism and how these have led to the consumptogenic society we are in. It aims to illustrate the nexus between the Māori and Western Eurocentric worlds.

He Whatu is the framework that has emerged from this case study as the means to respond to the primary research question. The framework was developed by analyzing the key themes of PKP over the years 2017 to 2021. He Whatu has five key elements: Identity, Language, Distance, Practicality, and Influence; each with three subcategories. It is activated through provoking key conversations to inform future community action.

year: 2023