Classification of New Zealand's Coastal Hydrosystems
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A classification of New Zealand's coastal hydrosystems Prepared for Ministry of the Environment October 2016 Prepared by: T. Hume (Hume Consulting Ltd) P. Gerbeaux (Department of Conservation) D. Hart (University of Canterbury) H. Kettles (Department of Conservation) D. Neale (Department of Conservation) For any information regarding this report please contact: Iain MacDonald Scientist Coastal and Estuarine Processes +64-7-859 1818 [email protected] National Institute of Water & Atmospheric Research Ltd PO Box 11115 Hamilton 3251 Phone +64 7 856 7026 NIWA CLIENT REPORT No: HAM2016-062 Report date: October 2016 NIWA Project: MFE15204 Quality Assurance Statement Reviewed by: Dr Murray Hicks Formatting checked by: Alison Bartley Approved for release by: Dr David Roper © All rights reserved. This publication may not be reproduced or copied in any form without the permission of the copyright owner(s). Such permission is only to be given in accordance with the terms of the client’s contract with NIWA. This copyright extends to all forms of copying and any storage of material in any kind of information retrieval system. Whilst NIWA has used all reasonable endeavours to ensure that the information contained in this document is accurate, NIWA does not give any express or implied warranty as to the completeness of the information contained herein, or that it will be suitable for any purpose(s) other than those specifically contemplated during the Project or agreed by NIWA and the Client. Contents Executive Summary .......................................................................................................................5 1 Introduction ........................................................................................................................7 2 The classification .................................................................................................................9 3 Geomorphic class ............................................................................................................... 12 3.1 Characteristics of geomorphic classes ...............................................................................12 3.2 Composite systems ............................................................................................................24 3.3 Stability of geomorphic classes ..........................................................................................24 4 Inventory of environmental variables ................................................................................. 28 4.1 The database ......................................................................................................................28 4.2 Distribution of coastal hydrosystems in New Zealand ......................................................28 5 Applications to management ............................................................................................. 33 5.1 Mapping systems and conservation and restoration planning .........................................33 5.2 Catchment land and water use planning and consenting .................................................34 5.3 Recognising values, threats and effects to coastal hydrosystems ....................................35 6 References ......................................................................................................................... 41 7 Acknowledgements ........................................................................................................... 48 8 Glossary ............................................................................................................................ 49 Appendix A Review of terminology associated with coastal hydrosystems ..................... 66 Appendix B Determination and naming of the geomorphic classes ................................ 72 Appendix C Identification key ....................................................................................... 75 Appendix D Google Earth images and schematics of geomorphic classes ........................ 80 Appendix E Inventory of environmental variables ......................................................... 92 Tables Table 2-1: How the hydrosystem and geomorphic class levels nest within a wider hierarchical classification. 9 Table 3-1: Geomorphic classes and 21 subclasses in the classification. 12 Table 3-2: Distinguishing characteristics of the geomorphic classes and subclasses. 13 Table 3-3: Summary of the temporal and spatial dynamics of geomorphic classes and subclasses. 25 Table 4-1: Distribution of coastal hydrosystems geomorphic classes by council region in New Zealand. 30 A classification of New Zealand's coastal hydrosystems 3 Table 4-2: Some key distinguishing characteristics of coastal hydrosystems in New Zealand. 32 Table 5-1: Services, values and uses for coastal hydrosystems. 38 Table 5-2: Threats to coastal hydrosystems. 39 Table 5-3: Effects of stressors on coastal hydrosystems. 40 Figures Figure 3-1: Clutha River, Otago. 27 Figure 3-2: Waimakariri River, Canterbury. 27 Figure 3-3: Lake Grassmere, Marlborough. 27 Figure 3-4: Orakei Basin, Auckland. 27 Figure 4-1: Distribution of the various geomorphic classes of coastal hydrosystem throughout New Zealand. 31 Figure 5-1: This example adapted from Hume et al. (2007) shows mapping of unmodified (green) and highly modified (red) estuaries. 34 4 A classification of New Zealand's coastal hydrosystems Executive Summary New Zealand has a long (18,000 km including estuarine shores) and highly varied coastline. New Zealand’s coastal water bodies, flowing and still, fresh to saline, span a wide range of environments; coastal wetlands; systems fed by small streams to large braided rivers; systems located at the interface of low to high-energy ocean settings; systems on muddy through sandy to gravelly coasts; and also large complex systems that are made up of several types or classes. The coastal hydrosystems classification described herein aims to reconcile and clarify coastal hydrosystem terminology and produce a hierarchy and classification of coastal wetland, riverine, estuarine and marine types. This report also provides some environmental parameters for the systems and gives examples of how the classification can be used to manage these systems and their catchments. The work began in June 2013 with workshops in June 2013 and January 2014 to explore ideas and the co-authors presenting ideas at conferences. In October 2015 MFE provided funding for NIWA, Hume Consulting Ltd and the University of Canterbury to work with the Department of Conservation to develop the classification further. Input from practitioners at a two-day stakeholders’ workshop in February 2016 contributed to the development of the classification and ensured its alignment with management applications. Many different terms are employed to describe these coastal hydrosystems, often in conflicting or confusing ways, in common language, scientific literature, legislative and planning documents. We have adopted the term “coastal hydrosystem” to describe coastal features that span a gradient from near coast freshwater lakes/wetlands (lacustrine/palustrine environments) to marine. This label avoids many pitfalls: it avoids mistakenly labelling all systems estuaries; it encompasses hydrosystems that are not end-of-river environments as well as large systems with multiple freshwater features; and unlike “waterbody”, it incorporates geomorphic, ecological and hydrological aspects of each system. In this report we provide a review (along with a glossary) of terms used to describe different kinds of coastal hydrosystems in use in common, statutory and scientific language and explain why precise definitions are important for coastal management. The coastal hydrosystems classification is based on a hierarchical view of the abiotic components that comprise the environments of coastal hydrosystems. Our classification presents detail at the geomorphic class level (III) of the hierarchy because this level is particularly important for coastal management and conservation needs at national and regional scales. However, to provide the wider context, we show how this can nest within a wider six-level hierarchy. Detail at levels IV to VI is best developed for specific management needs at the local scale using the description of structural and compositional habitat features. Geomorphic class, Level III of the hierarchy, sees hydrosystems defined as single type units/systems (or classes), each with associated characteristics. The classification recognises 11 geomorphic classes that are different enough from each other in their properties and the way they respond to natural and anthropogenic forcings that they need to be considered separately for management purposes. To keep the total number of classes small but at the same time recognise that some have a wide variety of characteristics that have different management implications, some classes have subclasses. Composite systems occur where a system contains subsystems representing different geomorphic classes. Whether a composite system is classified as a single class or a collection of several classes depends on the management question. The geomorphic classes are representative of types of systems that have been largely unmodified by anthropogenic activities such as reclamation, dredging, road/rail causeways and river-channel diversions. They exclude systems that have been totally created by humans such as small coastal lakes and flooded pits created by