A classification of New Zealand's coastal hydrosystems
Creator
Water, Ministry for the Environment
Publisher
Water, Ministry for the Environment
Date
2016-12-20
Date
2017-01-27
Description
Coastal hydrosystems describe coastal features that span a gradient from near coast freshwater lakes/wetlands (lacustrine/palustrine environments) to marine. The term 'coastal hydrosystem' avoids the common error of referring to all such features as estuaries, mislabelling the numerous types that are non-estuarine and have different behavioural characteristics and management sensitivities from any truly estuarine environment. It also encompasses the coastal systems that do not represent end-of-river environments (e.g., some pocket beaches and embayments) or are so large and complex as to be fed by several freshwater drainage features (rivers, streams, wetlands) but which are dominated by none (e.g., some harbours, fjords, sounds and coastal-lacustrine systems). It also incorporates the multiple aspects of each system, including beaches, spits, barriers, river mouths, wetlands, saltmarshes and other geomorphic, ecological and hydrological features.
The New Zealand Coastal Hydrosystem classification (NZCH) is a classification of coastal hydrosystems within New Zealand including some offshore islands. The coastal hydrosystems classification is based on a hierarchical view of the abiotic components that comprise the environments of coastal hydrosystems. This classification presents detail at the geomorphic class level because this level is particularly important for coastal management and conservation needs at national and regional scales.
The primary GIS is the point layer. Supporting files (attached) include: a CSV database of environmental variables; GIS polygon layer; and Google Earth (.kmz) point and polygon exports.
The database, GIS and Google Earth files should be used in conjunction with the Classification of New Zealand's Coastal Hydrosystems report (Hume et al. 2016) (also attached) which documents a full description of the database, the calculation procedures and limitations to the variables.
The spreadsheet comprises a database of 500 New Zealand coastal hydrosystems and their associated environmental variables developed for the report.
The GIS point file comprises 500 New Zealand coastal hydrosystems and their associated environmental variables developed for the database. The environmental variables are mapped at 1:50,000 scale. NOTE: Within the point attribute file -9999 represents the environmental variables with no data as shown in the spreadsheet as a blank cell. Make sure to exclude these values from analyses.
The polygon files comprise 420 New Zealand coastal hydrosystems depicting their general shape of the water body basin at high tide and upstream limit.
The .kmz files are derived from the NZCH GIS point and polygon layers for use with Google Earth.
The report provides a classification of coastal hydrosystems within New Zealand including some offshore islands. The coastal hydrosystems classification reconciles and clarifies coastal hydrosystem terminology and produces a hierarchy and classification of coastal wetland, riverine, estuarine and marine types. This report identifies and provides a list of environmental variables that describe the characteristics and properties of about 500 discrete coastal hydrosystems that can be used to provide national and regional statistics on coastal hydrosystems. An Identification Key is provided to guide the determination of the classes.
Source
Data mining and computation using numerical and analytical models and GIS were used to derive the NZCH database. Variables were derived from NIWA’s digital elevation model (DEM) (30 m cell size) of New Zealand, the 1:50,000 Digital Topographic Database, the New Zealand Land Resource Inventory (NZLRI) and Land Cover Database (LCDB) and the New Zealand EEZ Tidal Model, digital files of the RNZN hydrographic charts, and various publications and reports. Computation using numerical and analytical models and GIS was also used to derive the variables.
A full description of the database and calculation methods is provided in:
Hume, T., Gerbeaux, P., Hart, D., Kettles, H., Neale, D. 2016. A classification of New Zealand's coastal hydrosystems. Report prepared for the Ministry for the Environment. Niwa Client Report 2016-062. 120pp. October 2016.
This database comprises information from two sources. The first is the database developed for over 400 estuaries in the Estuarine Classification Database of Hume et al. (2007): Hume, T., Snelder, T., Weatherhead, M., Liefting, R. (2007) A controlling factor approach to estuary classification. Journal of Ocean and Coastal Management 50, Issues 11–12: 905–929. http://dx.doi.org/10.1016/j.ocecoaman.2007.05.009
It provides the following variables: Council region; Geomorphic class (NZ coastal hydrosystem classification); Coordinates of mouth (NZTM2000); Width of mouth (m); Shoreline perimeter length (m); Surface area at spring high tide (m2); Intertidal area (% of high tide area); Mean depth at spring high tide (m); Total volume at spring high tide (m3); Spring tidal range (m); Spring tidal prism (m); Catchment area (km2); River inflow volume during a tidal cycle, 12.4 hr (m3); Coordinates of mouth (NZMG).
It is important to note that this database was compiled over 2003-2006 and that there is now more up-to-date information available for some of the variables via the NZ River Environment Classification (REC2) and in particular, updates to the LCDB and Google Earth imagery. This has not been incorporated into the NZCH database.
The second source is data compiled as part of this study to incorporate environmental variables for damp sand plain lakes, waituna-type lagoons, hāpua-type lagoons, beach streams and freshwater river mouths systems. For these systems the dataset of variables is more limited because for instance waituna-type lagoons, hāpua-type lagoons, beach streams and freshwater river mouths have no tidal incursion and therefore no tidal prism or intertidal area.
Disclaimer - This dataset was created for the purpose of developing and testing a classification for New Zealand coastal hydrosystems. Its accuracy and integrity reflects that purpose. We recommend that users exercise their own skill and care with respect to their use of the data and that users carefully evaluate its accuracy, currency, completeness and relevance of it for their particular purposes. MFE does not guarantee, and accepts no legal liability whatsoever arising from, or connected to, the use of this dataset.
