REPORT Greater Wellington Regional Council Resource Consent Applications Hutt River/ Te Awa Kairangi Report prepared for: Greater Wellington Regional Council (Flood Protection) Report prepared by: Tonkin & Taylor Ltd Distribution: Greater Wellington Regional Council copy Tonkin & Taylor Ltd (FILE) copy March 2013 T&T Ref: WORKING DRAFT Table of contents 1 Introduction 6 1.1 Applicant and details of area covered by application 8 1.2 Land tenure 9 1.2.1 Hutt River corridor 9 1.2.2 Tributary streams 9 1.3 Summary of consent requirements 10 1.4 Interpretation 13 2 Background 16 2.1 Historical perspective 16 2.2 The Hutt River Floodplain Management Plan 16 2.2.1 Design Standard 17 2.3 Scale and impacts of flood hazard 17 2.4 Current Consents and Compliance 18 2.4.1 WGN 900255 19 2.4.2 WGN 060334 20 2.4.3 WGN 060291 20 2.4.4 WGN 110149 20 3 Existing Environment 22 3.1 River character & existing works 22 3.1.1 Moera/Petone Reach 22 3.1.2 Lower Hutt/CBD/Alicetown Reach 23 3.1.3 Boulcott Reach 23 3.1.4 Belmont/Taita Reach 24 3.1.5 Manor Park Reach 24 3.1.6 Heretaunga Reach 25 3.1.7 Moonshine Reach 25 3.1.8 Upper Hutt/Totara Park Reach 26 3.1.9 Akatarawa Reach 26 3.1.10 Te Mome Stream 27 3.1.11 Speedy’s Stream 27 3.1.12 Stokes Valley Stream 28 3.1.13 Akatarawa River 29 3.2 Geology 30 3.2.1 General 30 3.2.2 Lower Hutt basin 30 3.2.3 Upper Hutt basin 31 3.3 Hydrology 31 3.3.1 Hutt River catchment 31 3.3.2 Flow statistics 32 3.3.3 Flood flows 33 3.4 Sediment Transport 33 3.4.1 Features and controls 33 3.4.2 Volumes passing Taita Gorge 34 3.4.3 Gravel transport rates 35 3.4.4 Optimum river bed levels 36 3.5 Vegetation 36 3.6 Water quality 37 3.7 Aquatic ecology 41 Resource Consent Applications Hutt River/ Te Awa Kairangi T&T Ref. WORKING DRAFT Greater Wellington Regional Council March 2013 3.7.1 Aquatic Plants 41 3.7.2 Macroinvertebrates 42 3.7.3 Fish 45 3.7.4 Habitat mapping 48 3.8 Birdlife 49 3.9 Natural character 49 3.10 Landscape character 50 3.11 Recreation 50 3.11.1 Fishing 50 3.11.2 Paddling 51 3.11.3 Swimming 51 3.11.4 Walking and cycling 52 3.11.5 Golf 52 3.11.6 Parks and sportfields 53 3.11.7 Recreational use of tributaries 53 3.12 Tourism 53 3.13 Neighbouring community 53 3.13.1 Population 53 3.13.2 Infrastructure and services 54 3.14 Tangata whenua 56 3.15 Archaeological sites 58 4 Proposed Activities 59 4.1 Purpose and intended outcomes 59 4.1.1 Maintenance of channel alignment 59 4.1.2 Maintenance of channel capacity 60 4.1.3 Maintenance of existing flood defences 60 4.2 Description of activities 60 4.2.1 Overview 60 4.2.2 Diversion of water 83 4.2.3 Discharge of sediment 83 4.2.4 Gravel extraction 87 4.3 Design of annual work programmes 94 4.3.1 Gravel extraction 94 4.3.2 Other works 94 5 Consideration of Alternatives 96 6 Assessment of Environmental Effects 97 6.1 Positive effects 97 6.2 Construction of impermeable erosion protection structures 97 6.3 Establishment of vegetative bank protection 97 6.3.1 Clearance of flood debris 97 6.3.2 Beach vegetation removal (scalping) 97 6.3.3 Willow planting 97 6.3.4 Willow cutting/removal 97 6.3.5 Bed recontouring 98 6.3.6 Gravel extraction 98 6.3.7 Discharges 99 6.3.8 Cumulative effects 99 7 Adaptive Management 112 8 Consultation 114 9 Mitigation 115 Resource Consent Applications Hutt River/ Te Awa Kairangi Job no. WORKING DRAFT Greater Wellington Regional Council March 2013 10 Proposed conditions of consent 116 11 Statutory assessment 117 11.1 RMA assessment 117 11.1.1 Part 2 of the RMA 117 11.1.2 National Environmental Standards 117 11.1.3 National Policy Statements 117 11.1.4 Regulations 118 11.1.5 Regional Policy Statement 118 11.1.6 Regional Plans 119 11.2 Other matters 132 11.2.1 Hutt River Floodplain Management Plan 132 11.2.2 Long Term Plan 132 11.2.3 GWRC Asset Management Plan 134 11.3 Notification 134 12 Summary and Conclusions 135 13 References 136 14 T&T to be added Applicability 137 Appendix A: Consent application forms Appendix B: Private land in the river corridor Appendix C: Williams (2013) Appendix D: Photographs of proposed activities Appendix E: Gravel extraction construction plans Appendix F: TRC Report (Young 2012) Appendix G: MWH Report (Cameron 2013) Figure 1: Explanation of terms Figure 2: Te Mome Stream. Source: (Wellington Regional Council, Pollution Control Team, 2005) Figure 3: Speedys Stream, showing the reach included in this application. Figure 4: Stokes Valley Stream, showing the reach included in this application. Source: Google Earth Figure 5: Akatarawa River, showing the reach included in this application. Source: Google Earth Figure 6: Flow record for Hutt River at Taita Gorge (1979 -2010). Source: (Opus International Consultants Ltd, 2010) Figure 7: Comparison of total sediment volumes estimated from both modelling and measurement. Source: (Opus International Consultants Ltd, 2010) Figure 8: Port Nicholson Block (Source: Port Nicholson Block Settlement Trust website) Figure 9: ‘Wet’ gravel extraction: bulldozer forming low flow channel Figure 10: Wet’ gravel extraction: cutting new low flow channel through existing beach Figure 11: Wet’ gravel extraction: new low flow channel formed through existing beach to create new meander pattern. Figure 12: Gravel extraction: shaped low flow channel and stockpiled material Figure 13: Gravel extraction: front-end loader loading an off-road dumper truck Figure 14: Gravel extraction: off-road dumper crossing river Figure 15: The Adaptive Management framework Resource Consent Applications Hutt River/ Te Awa Kairangi T&T Ref. WORKING DRAFT Greater Wellington Regional Council March 2013 Table 1: Hutt River & catchment information Table 2: Hutt River flow statistics Table 3: Hutt River flood flows for Taita Gorge gauging station Table 4: Annual average sediment transport volumes passing through Taita Gorge Table 5: RSoE Monitoring Site Details – Hutt River Catchment Table 6: Summary of water quality data and compliance with guideline/trigger values for Hutt River sites within application area, sampled monthly July 2008 –June 2011 Table 7: Summary of water quality data and compliance with guideline/trigger values for Hutt River sites within application area, sampled monthly July 2008 –June 2011 - continued Table 8: Streambed periphyton cover Table 9: Species richness and MCI values from three Hutt River sites on January 1996. Table 10: Mean macroinvertebrate metric scores at selected RSoE sites, based on samples collected annually in 2009, 2010, 2011. MCI & QMCI quality classes also indicated. Table 11: Summary of NZFFD sent in Hutt River Table 12: Overnight fishing survey at two deepwater sites in the Hutt River Table 13: Population figures for Lower and Upper Hutt Table 14: Summary of operations and maintenance activities Table 15: Description of construction activities Table 16: Description of activities involving demolition or maintenance of structures Table 17: Description of other works Table 18: Turbidity and suspended solids (SS) monitoring results for the Hutt River during gravel excavation by bulldozer in flowing water 500m Upstream of Kennedy Good Bridge on 28 November 2012 Table 19: Turbidity and suspended solids monitoring results for the Hutt River during Moxy truck crossings of the river 500m Upstream of Kennedy Good Bridge on 28 November 2012 Table 20: Suspended solids concentrations in Waikanae River below works. Table 21: Gravel volumes extracted since November 2006 Table 22: Key Activities: Assessment of Effects Table 23: RFP - objectives and policies assessment Table 24: GWRC flood protection and control works capital expenditure programme 2012/13 to 2021/22 Table 25: GWRC flood protection works annual operating and capital expenditure Resource Consent Applications Hutt River/ Te Awa Kairangi Job no. WORKING DRAFT Greater Wellington Regional Council March 2013 6 1 Introduction Background to the need for flood protection operations and maintenance Flood protection works have been undertaken in the Hutt River for almost 150 years, and today the intensively developed floodplain of the Hutt Valley is protected by flood protection infrastructure that is valued at $66.2 M. The river has been modified and managed since European settlement of the Hutt Valley commenced, and it will continue to be modified and managed to protect the communities that live adjacent to it, for the foreseeable future. The requirement to address the flood hazard associated with rivers is enshrined in legislation 1, with the Greater Wellington Regional Council (GWRC) assuming responsibility for this function in the Wellington Region. Flood protection and control works makes up 6% (or nearly $12 M) of the council’s expenditure for the current financial year. The overarching vision and strategy for flood protection work in the Hutt River is contained in the Hutt River Floodplain Management Plan (HRFPMP)(Wellington Regional Council, 2001), a document that has been developed through consultation and agreement with the local Hutt Valley communities. This document establishes the level of protection from flooding that has been agreed with the three councils and the community, and it outlines the measures by which it will be achieved. These measures include capital works such as construction of stopbanks, operational works within the river, and other off-river works (such as moving people and infrastructure away from the flood risk).