Figure 1. Flow-chart outlining data used in the karst condition assessment to derive a Naturalness score (N-score). Note: where indicated variables were combined using expert rule systems.Find further information on the Conservation of Freshwater Ecosystem Values (CFEV) Program and its data at www.dpipwe.tas.gov.au/cfev.
TitleKarst naturalness score
CustodianWater and Marine Resources Division, Department of Primary Industries, Parks, Water and Environment
CreatorSteve Carter, Environmental Dynamics
DescriptionAn index which rates the relative ‘naturalness’ or condition of karst based on a selection of input variables.
Input data
Lineage
A condition assessment was undertaken for karst systems that considered impacts associated with their proximal and distal catchments. These included changes in hydrology, sediment flux and water chemistry. Figure 1 illustrates all the inputs that were either directly or indirectly used to generate an overall biophysical Naturalness score (N-score) for karst. Some of the variables (including the final N-score) were calculated using expert rules systems as indicated. Information on expert rules systems can be found in Appendix 3 of the CFEV Project Technical Report., as illustrated in Figure 1.
The interconnectivity of karst systems with the ground above means that activities on the surface often translate to impacts beneath the ground. Hence, impacts associated with certain land use practices within the karst catchment largely flow through to underground karst systems via fluvial systems. Large rivers flowing through karst areas are believed to have a smaller influence on karst condition and as such, a weighting was applied to the condition variables of abstraction index, regulation index and sediment flux to reflect this.
Figure 1. Flow-chart outlining data used in the karst condition assessment to derive a Naturalness score (N-score). Note: where indicated variables were combined using expert rule systems.
The last step in the karst condition assessment is described in more detail here. An overall N-score was generated for karst areas using an expert rules system with the inputs of the hydrology sub-index, sediment flux and water chemistry (see ‘Assigning values to ecosystem spatial units’).
The hydrology and sediment flux sub-indices were both weighted greater than the water chemistry sub index. Physical sensitivity (exposed or covered karst) and catchment size were included in the expert rule system to provide a context for the N-score.
Date createdJanuary 2005
Scale and coverage1:25 000; Statewide
Column headingKT_NSCORE
Type of dataContinuous but has been converted to categorical format (see Table 3).
Number of classes3
Assigning values to ecosystem spatial units
An N-score (0 = poor condition – 1 = good condition) was assigned to karst spatial units as KT_NSCORE using the expert rule systems shown as a definition tables in Tables 1 and 2. Table 1 shows the definition table for when the karst’s catchment size is small (i.e. KT_CATCH = 0) while Table 2 presents the rules to apply when the karst’s catchment size is big (i.e. KT_CATCH = 1). An additional context was set to take into account the physical sensitivity of the karst area (i.e. whether the karst is exposed or covered). An example of applying the rules is that if the karst’s catchment size is small, and it has a HIGH score for sediment flux, a HIGH score for water chemistry and a LOW score hydrology, then assign a score of 0.6 if the karst area is exposed, otherwise assign 0.8). 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 naturalness score for karst, for when catchment size is small (KT_CATCH = small (0)).
Sediment Flux (Catchment disturbance) (KT_CATDI) | Water Chemistry (Catchment disturbance) (KT_CATDI) | Hydrology (KT_HYDRO) | Naturalness score (KT_NSCORE) where Physical sensitivity (KT_PHYSSEN) = 0 (exposed) | Naturalness score (KT_NSCORE) where Physical sensitivity (KT_PHYSSEN) = 1 (covered) |
H | H | H | 1 | 1 |
H | H | L | 0.6 | 0.8 |
H | L | H | 0.7 | 0.85 |
L | H | H | 0.6 | 0.8 |
H | L | L | 0.4 | 0.5 |
L | H | L | 0.2 | 0.4 |
L | L | H | 0.4 | 0.5 |
L | L | L | 0 | 0 |
Table 2. Expert rules system definition table for the naturalness score for karst, for when catchment size is small (KT_CATCH = big (1)).
Sediment Flux (Catchment disturbance) (KT_CATDI) | Water Chemistry (Catchment disturbance) (KT_CATDI) | Hydrology (KT_HYDRO) | Naturalness score (KT_NSCORE) where Physical sensitivity (KT_PHYSSEN) = 0 (exposed) | Naturalness score (KT_NSCORE) where Physical sensitivity (KT_PHYSSEN) = 1 (covered) |
H | H | H | 1 | 1 |
H | H | L | 0.65 | 0.7 |
H | L | H | 0.8 | 0.8 |
L | H | H | 0.65 | 0.7 |
H | L | L | 0.4 | 0.5 |
L | H | L | 0.3 | 0.4 |
L | L | H | 0.45 | 0.5 |
L | L | L | 0.2 | 0.3 |
The karst spatial data layer has the continuous naturalness data categorised according to Table 3. The categorical data was used for reporting and mapping purposes.
Table 3. Naturalness categories for karst areas.
Category | Min to max values |
Low | 0 to 0.6 |
Medium | >0.6 to 0.85 |
High | >0.85 to 1 |
CFEV assessment framework hierarchy