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TitleRiver sediment input sub-index
CustodianWater and Marine Resources Division, Department of Primary Industries, Parks, Water and Environment
CreatorSteve Carter, Environmental Dynamics
DescriptionAn index which rates the impact of sediment input on rivers according to catchment disturbance, urbanisation and mining sedimentation.
Input data
Lineage
A set of rules were developed to relate changes in anthropogenic influences to in-stream geomorphic condition. Sediment input was calculated as a sub-index using an expert rule system (see ‘Assigning values to ecosystem spatial units’ below). Information on expert rules systems can be found in Appendix 3 of the CFEV Project Technical Report. The primary inputs to this expert rule system were records of catchment disturbance (primarily vegetation clearance) and urbanisation. Impacts associated with historical mining sedimentation provided a context for the sediment input scores. Urbanisation was weighted in the expert rule system as having more of a local influence on sediment input than catchment disturbance.
The method for assigning a sediment input sub-index score to the river spatial units is provided below.
Date createdNovember 2004
Scale and coverage1:25 000; Statewide
Column headingRS_SEDIN
Type of dataContinuous but has been converted to categorical format (see Table 2).
Number of classes5
Assigning values to ecosystem spatial units
A sediment input sub-index score (0 = poor condition – 1 = good condition) was assigned to river spatial units as RS_SEDIN using the expert rule system shown as a definition table in Table 1. A context was set to take into account the presence of mining sedimentation (i.e. RS_MINES is 1 = absent or 0 = present). An example of applying the rules is that if the river section has a HIGH score for urbanisation and a LOW score for catchment disturbance, and mining sedimentation is present, then assign a score of 0.2). Using fuzzy logic enables input data and output results to be continuous rather than categorical as implied here (i.e. inputs and output data can range on a continuous scale between 0 and 1, and the process of executing the expert rule system will determine its membership as being HIGH or LOW) (refer to Appendix 3 of the CFEV Project Technical Report for more information on expert rules systems).
Table 1. Expert rules system definition table for the sediment input sub-index for rivers.
Urbanisation (RS_URBAN) | Catchment disturbance (RS_CATDI) | Sediment input score (RS_SEDIN) with Mining sedimentation (RS_MINES=1) | Sediment input score (RS_SEDIN) with Mining sedimentation (RS_MINES=0) |
H | H | 1 | 0.4 |
H | L | 0.4 | 0.2 |
L | H | 0.2 | 0.1 |
L | L | 0 | 0 |
The rivers spatial data layer has the continuous sediment input sub-index data categorised according to Table 2. The categorical data was used for reporting and mapping purposes.
Table 2. Sediment input sub-index categories for rivers.
Category | Min to max values |
1 | 0 to <0.2 |
2 | 0.2 to <0.4 |
3 | 0.4 to <0.8 |
4 | 0.8 to <1 |
5 | 1 |
CFEV assessment framework hierarchy