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TitleLand disturbance within saltmarshes sub-index
CustodianWater and Marine Resources Division, Department of Primary Industries, Parks, Water and Environment
CreatorSteve Carter, Environmental Dynamics
DescriptionAn index which rates the relative condition of saltmarshes according to land disturbance impacts (i.e. road/tracks and landfill) within saltmarshes.
Input data
Lineage
The land disturbance within saltmarshes sub-index was established using an expert rule system which included input variables that described the extent of landfill within and roads/tracks within saltmarshes (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. These input variables were assessed by inspecting aerial photograph and were scored between 0 (disturbed) and 1 (pristine) according to the details in Table 1.
Table 1. Summary of variables assessed using aerial photographs for land disturbance within saltmarshes condition variable.
Variables | Unit | Other comments |
Roads or tracks | 1 – absent, 0.5 – little, 0.25 – moderate, 0 – extensive | |
Landfill | 1 – absent, 0.5 – little, 0.25 – moderate, 0 – extensive | Apparent landfill associated with industrial, agricultural, housing or other developments inside the saltmarshes was recorded. |
The weighting for each input variable was landfill within > roads/tracks within. The method for assigning a land disturbance within saltmarshes sub-index score to the saltmarsh spatial units is provided below.
Date createdNovember 2004
Scale and coverage1:25 000; Statewide
Column headingSM_LDWIN
Type of dataContinuous but has been converted to categorical format (see Table 3).
Number of classes3
Assigning values to ecosystem spatial units
An land disturbance within saltmarshes sub-index score (0 = poor condition – 1 = good condition) was assigned to saltmarsh spatial units as SM_LDWIN using the expert rule system shown as a definition table in Table 2 (e.g. if the saltmarsh has a HIGH score for roads/tracks adjacent to saltmarshes, LOW score for urban development adjacent and HIGH score for landfill adjacent to saltmarshes, then assign a score of 0.5). 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 2. Expert rules system definition table for the land disturbance within saltmarshes sub-index for saltmarshes.
Roads/tracks within saltmarshes (SM_RDWIN) | Landfill within saltmarshes (SM_LFWIN) | Land disturbance within saltmarshes score (SM_LDWIN) |
H | H | 1 |
L | H | 0.4 |
H | L | 0.2 |
L | L | 0 |
The saltmarsh spatial data layer has the continuous impacts within saltmarshes sub-index data categorised according to Table 3. The categorical data was used for reporting and mapping purposes.
Table 3. Land disturbance within saltmarshes sub-index categories for saltmarshes.
Category | Min to max values |
1 | 0 to <0.2 |
2 | 0.2 to <0.8 |
3 | 0.8 to 1 |
CFEV assessment framework hierarchy