Suspended Sediment Yield Estimator (SSYE)


A New Zealand national GIS ‘layer’ to enable reconnaissance-scale estimation of suspended-sediment yields from New Zealand’s rivers and streams. It has been developed by NIWA in collaboration with Landcare Research. Predicting long-term average suspended-sediment loads in rivers and streams is useful for dealing with a variety of issues. These include sediment entrapment rates in potential reservoirs and the vulnerability of estuarine and coastal marine habitats to sediment influxes from the land.


SSYE uses a raster-based GIS layer of specific suspended-sediment yield (SSY, t/km2/y) from New Zealand’s rivers and streams has been generated based on gauged sediment yields at over 200 river stations and an empirical model. The model relates sediment yield per unit area to mean annual rainfall and to an ‘erosion terrain’ classification, and has been calibrated off the river-gauging data. The erosion terrains were defined by Landcare Research on the basis of slope, rock type, soils, dominant erosion processes, and expert knowledge.

The resulting map of sediment delivery to rivers and streams has been adjusted over the gauged catchments so that the sediment yield predicted by the empirical model matches the gauged yields. The layer can be used to estimate suspended-sediment delivery to rivers and streams from within any defined catchment boundary. It was developed as a series of GRID files within the ARC GIS system.

Latest Version 2007
State of Development Stable Release
Current Development Activity None

Development Contact

Murray Hicks
+64 3 3437872
National Institute of Water and Atmospheric Research (NIWA)
41 Market Place
Viaduct Harbour
Auckland Central 1010
Private Bag 99940
Newmarket, Auckland 1149
New Zealand

Main Developers

  • National Institute of Water and Atmospheric Research (NIWA)


Outcome Areas Environmental
Management Domains Land, Natural Hazards, Biodiversity
Subdomains Contaminant Losses, Erosion/Sediment, Coast, Hazards
Intended End Users Researchers, Regional Coucil staff, environmental consultants
Spatial Resolutions 100-500m
Spatial Extents National
Spatial Dimensions 2D
Temporal Resolutions Not applicable
Temporal Extents Decades
Steady State or Dynamic Steady State
Level of Integration Environmental

Input & Output Data

Key Input Data Select location (river) of interest
Input Data Formats User-selected map location
Key Output Data River sediment yield past selected location
Output Data Formats Image File(s) Screen output


Open/Closed Source Closed Source
Licence Type No Licence

User Information

Operating Systems Web-based
Software Needed Web browser
User Interface Unknown Any PC
Ease of Use Easy

Help page on web-site Pilot version available for download:

Support None
Users Forum None

Technical Considerations

Programming Language NA
Methods included for calibration and validation NA
Methods included for managing uncertainty NA
Analytical Techniques Input/output
Model Structure

Model identifies cachment upstream of selected river reach on River environment Classification channel network, then integrates sediment yield over a yield per unit area surface masked by the catchment boundary.

Keywords sediment, sediment yield, river, stream

NIWA Suspended-sediment yield estimator -

Key References

Hicks, D.M.; Shankar, U.; McKerchar, A.I. (2003): Sediment Yield Estimates - a GIS tool. Water and Atmosphere 11(4)

Hicks, D.M.; Shankar, U.; McKerchar, A.I.; Basher, L.; Lynn, I.; Page, M.; Jessen, M. (2011). Suspended sediment yields from New Zealand rivers. Journal of Hydrology (New Zealand) 50(1): 81.