Sediment budgets for river Networks (SedNet)


SedNet identifies sources and sinks of sediment and nutrients in river networks and predicts spatial patterns of erosion and sediment load. SedNet constructs sediment and nutrient (phosphorus and nitrogen) budgets for regional scale river networks (3,000 - 1,000,000 km2) to identify patterns in the material fluxes. This can assist effective targeting of catchment and river management actions at the regional scale, to improve water quality and riverine habitat.


SedNet has been designed for a range of different users with different backgrounds, however modelling sediment and nutrient budgets is a complex activity. GIS and data analysis experience is required for initial construction of a catchment SedNet model. Experience and knowledge of landscape processes are valuable aids in interpreting model operation and results.

SedNet is an Australian model (eWater Toolkit) which is being adapted for New Zealand conditions by Landcare Research (SedNetNZ - SedNet for use in New Zealand).  The model has been trialled in the Manuwatu catchment,Motueka, Waipa catchment and Northland. The research into its application in New Zealand is ongoing.

In the model a budget is an account of the major sources, stores and fluxes of material. SedNet defines a stream network as a series of links extending between stream junctions, and constructs sediment and nutrient budgets for each link. Spatial modelling is used to combine measurements of river discharge, a basic understanding of material transport processes and geographical mapping of soils, vegetation cover, geology, terrain and climate. Details of the technical basis of SedNet are described in the SedNet User Guide.

SedNet allow for creating scenarios that targeting erosion control and other management measures to dominant sources and assess the benefits in reduced sediment and nutrient loads downstream and compare these with outcomes from non-targeted management. With careful data preparation, SedNet can assist planning of catchment management actions by identifying the relative importance of processes supplying sediment and nutrients to the river network, and hotspot areas of each source.

SedNet also accounts for deposition of sediment in the stream network. If the management objective is to reduce catchment export to limit downstream impacts, accounting for deposition is important because not all areas of erosion result in export of sediment from the catchment. Suspended sediment deposits in reservoirs and floodplains. Bedload sand and gravel can accumulate on the bed of rivers and degrade aquatic habitat, particularly along low-gradient reaches of streams when the upstream sediment supply is in excess of the reach's capacity to transport it.

The 'Material budgets' are constructed in SedNet using Configurations and Scenarios. A Configuration contains the stream network and several catchment attributes that do not change. It is the framework on which the budgets are constructed. Each Configuration can contain several Scenarios, each containing the datasets, parameters and results associated with a particular catchment condition, whether historical, present-day or a simulation of possible future condition.

The layout of the SedNet interface can be customised by arranging dockable windows to suit user requirements. The interface contains a Map Frame for viewing maps of input and output data.


 SedNet GUI

SedNet User Interface


The effect of proposed changes in catchment management on sediment and nutrient fluxes can also be simulated to set targets for future loads and to compare the relative effectiveness of different management strategies on long-term supply and yields from river networks.

See the eWater Toolkit website for more information on 'Features and Limitations'


Latest Version V2.0.0 Released Sept 2018
State of Development Released and updated

Development Contact

NZ Contact - John Dymond (


Outcome Areas Environmental
Management Domains Freshwater, Land
Subdomains Erosion/Sediment, Water Quality
Intended End Users
  • Researcher
  • Regional Council Scientist
  • Implementation Staff
Spatial Resolutions 10-100m, 100-500m
Spatial Extents Local (i.e. Catchment or District), Regional
Spatial Dimensions 2D, 3D
Steady State or Dynamic Unknown
Level of Integration Environmental

Input & Output Data

Key Input Data Land Cover, Land Use, Rainfall, Runoff DEM, Drainage network, stream flow and quality
Input Data Formats GIS compatible files
Key Output Data Water quality - contaminant flux and yield
Output Data Formats GIS Compatible Files


Open/Closed Source Closed Source
Licence Type No Licence

User Information

Operating Systems MS Windows
Software Needed GIS
User Interface Graphical desktop
Ease of Use Unknown
Use in Policy Process Review (Issue Identification), Plan (Policy Formulation)

User guide available for download from website

Technical Considerations

Programming Language Microsoft .NET
Analytical Techniques GIS
Model Structure

SedNetodule structure

Keywords sediment, nutrients, nitrogen, phosphorous, erosion, budgets, deposition, scenarios, land use change

 SedNet - eWater Toolkit Website

Key References

SedNet Publications - eWater Toolkit webpage

Markus U. Mueller and John R. Dymond (2015): SedNetNZ modelling of soil erosion in Northland. Landcare Research Contract Report: LC2424