A classification of New Zealand's coastal hydrosystems
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 gravel and goldmining activities. The key characteristics of each of the geomorphic classes and subclasses are described and illustrated using Google Earth images and schematics. This report identifies and provides a list of environmental variables that describe the characteristics and properties of about 500 discrete coastal hydrosystems. These can be used to provide national and regional statistics on coastal hydrosystems and answer questions such as: How many are there? Where are they located? How many do we have of certain classes? Which are rare in a region? Which is the biggest? Where are the marine versus freshwater dominated systems? While many small damp sand plain lakes and beach stream hydrosystems remain unclassified, the report offers guidance on how to classify these remaining systems. The report finally illustrates the management uses of the classification with examples of the value of using correct terminology, mapping the distribution of types and a multi criteria analysis approach showing how services, values, threats and effects in systems are associated with geomorphic classes/subclasses.
SubjectsField of Research::04 - Earth Sciences::0406 - Physical Geography and Environmental Geoscience::040603 - Hydrogeology
- Science: Reports