Waiapu River Catchment Study Final Report MPI Technical Paper No: 2012/32 Prepared by SCION ISBN No: 978-0-478-40446-3 (online) ISSN No: 2253-3923 (online) November 2012 Report Information Sheet Report Title: Waiapu River Catchment Study – Final Report Contributing Scion – T. Barnard, L. Barry, L. Garrett, D. Harrison, H. Jones, Authors D. Moore (alphabetical GNS Science – M. Page, B. Rosser order): Tina Porou – T. Porou Fitzgerald Applied Sociology – G. Fitzgerald University of Canterbury – M. Bloomberg, J. Morgenroth Peacock D H Ltd – D. Peacock Client: Ministry of Agriculture and Forestry Client Contract 15201 No: Sidney output 48874 number: Reviewed by: Brenda Baillie Signed off by: Peter Clinton Date: 13 June 2012 Intellectual © NEW ZEALAND FOREST RESEARCH INSTITUTE LIMITED Property: All rights reserved. Unless permitted by contract or law, no part of this work may be reproduced, stored or copied in any form or by any means without the express permission of the NEW ZEALAND FOREST RESEARCH INSTITUTE LIMITED (trading as Scion). Disclaimer: The information and opinions provided in the Report have been prepared for the Client and its specified purposes. Accordingly, any person other than the Client uses the information and opinions in this report entirely at its own risk. The Report has been provided in good faith and on the basis that reasonable endeavours have been made to be accurate and not misleading and to exercise reasonable care, skill and judgment in providing such information and opinions. Neither Scion, nor any of its employees, officers, contractors, agents or other persons acting on its behalf or under its control accepts any responsibility or liability in respect of any information or opinions provided in this Report. Report reference: Scion. (2012). Waiapu River Catchment Study –Final Report. Scion Confidential Client Report No. 15201. Rotorua, New Zealand: Scion. Chapter references: Chapter 1: Jones, H. S., Barnard, T. D., Barry, L., Bloomberg, M., Fitzgerald, G., Garrett, L. G., Harrison, D., Moore, D. J., Morgenroth, J., Page, M. J., Peacock, D. H., Porou, T., & Rosser, B. J. (2012). General introduction. In Scion. Waiapu River Catchment Study –Final Report (pp. 1-2). Scion Confidential Client Report No. 15201. Rotorua, New Zealand: Scion. Chapter 2: Rosser, B. J., Page, M. J., & Peacock, D. H. (2012). Literature review – a review of the geophysical & land use aspects of the erosion problem in the Waiapu catchment. In Scion. Waiapu River Catchment Study –Final Report (pp. 3-102). Scion Confidential Client Report No. 15201. Rotorua, New Zealand: Scion. Chapter 3: Barnard, T. D., Porou, T., Moore, D. J., Garrett, L. G., & Barry, L. (2012). Literature review & kōrero – impacts of land use change & erosion on Ngāti Porou in the Waiapu catchment. In Scion. Waiapu River Catchment Study –Final Report (pp. 103-137). Scion Confidential Client Report No. 15201. Rotorua, New Zealand: Scion. Chapter 4: Rosser, B. J., Page, M. J., Peacock, D. H., Bloomberg, M., & Morgenroth, J. (2012). Benchmarking, scope assessment, & critical evaluation – geophysical aspects. In Scion. Waiapu River Catchment Study –Final Report (pp. 138-172). Scion Confidential Client Report No. 15201. Rotorua, New Zealand: Scion. Chapter 5: Bloomberg, M., Morgenroth, J., Rosser, B.J., Page, M.J., Harrison, D., & Jones H. (2012). Erosion, land use, erosion control, & land tenure in the Waiapu catchment. In Scion. Waiapu River Catchment Study –Final Report (pp. 173-191). Scion Confidential Client Report No. 15201. Rotorua, New Zealand: Scion. Chapter 6: Porou, T., Barnard, T., Fitzgerald, G., Moore, D., Barry, L., Garrett, L., & Harrison, D. (2012). Benchmarking, scope assessment, & critical evaluation – social, cultural, & economic aspects of erosion for Ngāti Porou & a desired state for the Waiapu catchment. In Scion. Waiapu River Catchment Study –Final Report (pp. 192-259). Scion Confidential Client Report No. 15201. Rotorua, New Zealand: Scion. Chapter 7: Jones, H.S., Bloomberg, M., Page, M.J., Rosser, B.J., Porou, T., Barnard, T., Peacock, D.H., & Moore, D. (2012). Toward a desired state for the Waiapu River & catchment. In Scion. Waiapu River Catchment Study –Final Report (pp. 260-293). Scion Confidential Client Report No. 15201. Rotorua, New Zealand: Scion. Chapter 8: Jones, H. S., Barnard, T. D., Barry, L., Bloomberg, M., Fitzgerald, G., Garrett, L. G., Harrison, D., Moore, D. J., Morgenroth, J., Page, M. J., Peacock, D. H., Porou, T., & Rosser, B. J. (2012). Key conclusions. In Scion. Waiapu River Catchment Study –Final Report (pp. 294-295). Scion Confidential Client Report No. 15201. Rotorua, New Zealand: Scion. Executive summary This report presents the work undertaken on the Waiapu River Catchment Study, the purpose of which was to investigate the geophysical, social, cultural, and economic dimensions of the erosion problem in the Waiapu River catchment in order to inform future policy decisions with respect to the catchment in the context of the Deed of Settlement between Ngāti Porou and the Crown. The report includes: An outline of existing knowledge related to the (i) geophysical and land use aspects and (ii) social, cultural, and economic aspects of erosion and land use change within the Waiapu River catchment and the wider East Coast region. Identification of gaps in the existing knowledge apparent to the research team, and recommendations for addressing any gaps identified. A description of a baseline from which future progress in the Waiapu catchment may be measured (benchmarking) for the (i) geophysical and land use aspects and (ii) social, cultural, and economic aspects of erosion against the values of Ngāti Porou for the catchment and well-being of the people. An outline of the project team‘s interpretation of a desired state for Ngāti Porou and consideration of possible options for addressing the erosion problem. Assessments of the scope (size and scale) of the erosion problem in the catchment and critical evaluations of the effectiveness of erosion mitigation measures for the (i) geophysical aspects and (ii) social, cultural, and economic aspects of erosion. Main findings Outline of existing knowledge Geophysical & land use aspects The key points to emerge from the literature relating to the geophysical and land use aspects of the erosion problem in the catchment are: The Waiapu catchment is located in a dynamic tectonic and climatic setting. Recent and extensive deforestation has exacerbated the high natural rates of erosion and sedimentation. The response to deforestation has been rapid and pronounced. Research to date has provided some insight into landscape controls on sediment generation and transfer in the Waiapu catchment following deforestation. However, much of the research has been focused on gully erosion. i Extensive gully erosion commenced within one or two decades, and now accounts for 49% of the annual suspended sediment yield of 35 Mt, which is more than twice that of the adjacent Waipaoa River, the next highest yielding New Zealand River, and nearly ten times that of the Manawatu River. Similarly, channel responses to sudden fluctuations in sediment supply have been rapid with channels aggrading, and particularly in the lower reaches, widening markedly. Recent research also shows that land use/vegetation change is the most effective method of controlling erosion. Modelling indicates that planting all East Coast Forestry Project (ECFP) ‗target land‘ by 2020 is more effective than planting all Land Overlay 3A (LO3A) land, and the earlier this is achieved the greater the reduction in gully-derived sediment yield. However, sediment yield from gullies will still increase due to unplanted gullies, unstablised gullies, and new gullies on untreated areas outside the ECFP target land. The rates of erosion and relative sediment contribution by processes other than gully erosion (i.e. landslide, earthflow, sheetwash, streambank erosion, and river bed degradation) under different land uses and land management practices represents a significant research gap. These other processes account for 51% of the sediment yield. The gaps in existing knowledge limit our ability to identify the amount, mix, and spatial distribution of erosion mitigation measures (afforestation, reversion, and wide-spaced tree planting) required to improve geophysical conditions sufficient to achieve a ‘desired state‗ as identified by Ngāti Porou. More specifically, how much afforestation, reversion, and wide-spaced tree planting is required to affect a switch from aggradation to incision and how long it will take for the effects to manifest in the main stem of the Waiapu River are unanswered questions. Social, cultural, & economic aspects The key points to emerge from the literature relating to the social, cultural, and economic aspects (impacts on Ngāti Porou, in particular) of the erosion problem in the catchment are: The Waiapu catchment is of great spiritual, cultural, and economic significance to Ngāti Porou and the health of the catchment extends much further than the physical elements of the landscape. Many Ngāti Porou have had concerns about commercial forestry as a means to control erosion. The disestablishment of the New Zealand Forest Service and subsequent sale of forests had major impacts on Ngāti Porou communities and their view of Governmental agencies. Concerns that families and communities have become socially dislocated. ii Many Ngāti Porou seek mana motuhake over the river and catchment, and its restoration or healing. This is