Plugin was written by Andrew Freebairn, it is based on Scott Wilkinson's et al paper "Development of a time-stepping sediment budget model for assessing land use impacts in large river basins". It also borrows from the Dynamic SedNet plugin developed at DERM by Robin Ellis (Unlicensed) and Ross Searle (Unlicensed) (now at CSIRO).
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- Load the “dSedNet” plug-in using the 'Plugin Manager'
- Use the dSednetDerivedLayers to derive useful data. This tool removes the need to have a DEM saved within the project file. It also generates many of the spatial parameter layers used to parameterise the dSednet models and to construct the base scenario. Inputs required are, a hydrologically sound DEM, stream threshold (50km^2 is default), the easting and northing of the outlet cell (if one is not given all outlets will be produced at the edge of the data provided) and the file path to save results.
- Define a Source Catchments scenario using the “Geographic Wizard”. When defining the 'Network' use the option to 'Draw Network' and use the layers generated from the above process.
- Define FU areas with the use of a land-use map (raster) which covers 100% of the catchment (This is a prerequisite for using the Spatial Parameteriser)
- Select a rainfall runoff model and assign parameters/calibrate it
- Define constituents (e.g. “Fine” and “Coarse”).
- You may need to define multiple sources of constituents for a given functional unit (e.g. Hill slope and Gully)
- Assign models for constituent generation - (“Hillslope Model – dSedNet” and “Gully Model - dSedNet”) and enter static model parameters
- Assign spatial parameters to selected constituent generation models using the Spatial Parameterisation tool.
- Execute the temporal parameterisers for associated constituent generation models
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| Parameter | Description | Source |
|---|---|---|
| USLE HSDR - Fine | Hill sediment delivery ratio | Default 0.1 (Prosser et al, 2001) |
| R | rainfall erosivity factor | Internally calculated based on rainfall for the given timestep and uses Yang and Yu (1987) method |
| KLSC | Soil erodibility factor, slope length, steepness factor and cover factor (static) | K - Soil erodability (Wischmeier and Smith (1978)) L - Slope length (default, 1) S - Steepness raster generated by dSednetDerivedLayers for steepness factor C - Cover factor (Rosewell, 1993) |
| KLSCdynamic | Soil erodibility factor, slope length, steepness factor and cover factor | Where C is played as a time series to capture the temporal variance of vegetation cover. Perform raster operations, where static KLS are multiplied together to for a single KLS raster. Then for each daily C layer multiple with the KLS raster to produce a daily layers for KLSC. Use the spatial parameteriser the model, using t |
| S | mean summer rainfall | Internally calculated by the temporal parameterisation |
| P | mean annual rainfall | Internally calculated by the temporal parameterisation |
| R Factor Rainfall Threshold | R rainfall threshold | 12.7 mm (If daily rainfall is less than this threshold then the R value is set to 0) |
| Alpha | Rainfall erosivity factor used to calculate R | Calculated at runtime based upon S and P |
| Beta | Rainfall erosivity factor used to calculate R | Default values are set - 1.49, or use the Beta raster generated by dSednetDerivedLayers which uses Yang and Yu (1987) method |
| Eta | rainfall erosivity factor used to calculate R | Default, 0.389 (Yang and Yu, 1987) method |
| DWC | Dry Weather Concentration | User defined from literature |
| Off set from day of year | Number of days that are subtracted from the current day of year | Default, 15 |
| Daily Rain | Rainfall that fell on a single 24hrs measured in mm | This will be assigned at runtime by the system. It is obtained from the rainfall runoff model for the associated FU |
R is based on Yang et al (2015) - Yang Xihua, Yu Bofu (2015) Modelling and mapping rainfall erosivity in New South Wales, Australia. Soil Research 53, 178-189.
Beta base on on Yang et al (2015) - Yang Xihua, Yu Bofu (2015) Modelling and mapping rainfall erosivity in New South Wales, Australia. Soil Research 53, 178-189.
The parameter KLSC (static) (or KLSCdynamic, dynamic) can be provided to the model in a number of different ways.
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| Parameter | Description | Source |
|---|---|---|
| Link Slope | Average channel slope (m/m) | use the Reach slope raster generated by dSednetDerivedLayers) |
| Link Length | Length of main channel (m) | use the Reach length raster generated by dSednetDerivedLayers) |
| Link Width | Width of main channel (m)y | Currently not used |
| Link Depth | Channel Depth | Currently not used |
| Bank Height | Bank Height | Observations |
| Channel Roughness | Channel roughness | Mannings N value |
| Riparian Vegetation Percentage | Riparian Vegetation Percentage | Observations |
| Bank Full Flow | The flow when the stream is full to the top of the bank | Internally calculated by the temporal parameterisation |
| Bank Full Flow Annual Recurrence Interval | Annual Recurrence Interval of the flow when the stream is full to the top of the bank | User defined from literature |
| Max Riparian Vegetation Effectiveness | Riparian Vegetation Percentage - Effectiveness | User defined from literature |
| Soil Erodibility | Soil Erodibility % | Input layer - spatial parameterisation |
| Erosion Coefficient | Adjusted for long-term rates of bank retreat as observed (0.00001) | Observations |
| Soil Percent Fine Particles | Soil Percent Fine Particles % | Input layer - spatial parameterisation |
| Sediment Bulk Density | The weight (tonnes) of 1m3 of sediment | Input layer - spatial parameterisation |
| Long Term Average Daily Flow | Long Term Average Daily Flow raised to the Daily Flow Power Factor | Internally calculated by the temporal parameterisation |
| Daily Flow Power Factor | Used to manually fit data of bank erosion rates | Default to 1.4 |
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