Sediment budgets for river Networks (SedNet)

Purpose

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.

Description

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 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

Scope

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

Accessibility

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)
Documentation	User guide available for download from website http://www.toolkit.net.au/Tools/SedNet/documentation

Technical Considerations

Programming Language	Microsoft .NET
Analytical Techniques	GIS
Model Structure
Keywords	sediment, nutrients, nitrogen, phosphorous, erosion, budgets, deposition, scenarios, land use change
Links	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

Associated Case Studies