3.2.4 Assessing potential impacts for landscape classes and assets

The BA approach for assessing potential impacts for landscape classes (ecosystems) and water-dependent assets is discussed in companion submethodology M10 (as listed in Table 1) for analysing impacts and risks (Henderson et al., 2018). The zone of potential hydrological change focuses the attention of the analysis on areas where there may be changes in surface water and/or groundwater that are attributable to additional coal resource development.

The principal focus of the BA’s impact analysis is on water-dependent assets that are nominated by the community, or are recognised as being significant at state- or national-level (e.g. listed as a matter of national environmental significance under the Commonwealth’s Environment Protection and Biodiversity Conservation Act 1999). These assets may have a variety of values, including ecological, sociocultural and economic values. The water-dependent asset register (companion product 1.3 for the Galilee subregion (Sparrow et al., 2015); Bioregional Assessment Programme, Dataset 8) provides a simple and authoritative listing of the assets within the assessment extent. The register is a compilation of assets identified in databases compiled by several natural resource management groups in the Galilee subregion, as well as Australian and Queensland government databases. Additional assets were also supplied during several Galilee subregion BA assets workshops with various experts and organisations with local knowledge, held in September 2014 (in Longreach and Richmond), and October 2014 (in Brisbane). The identified assets compiled from all sources were assessed by the Assessment team for fitness for BA purpose, location within the assessment extent and water dependency. Assets that satisfied the requirements were considered in the impact and risk analysis reported in this product.

Landscape classification is fundamental to the impact and risk analysis and was used to discretise the heterogeneous landscape across the Galilee assessment extent into a manageable number of landscape classes for the impact and risk analysis. For BA purposes, a landscape class is an ecosystem with characteristics that are expected to respond similarly to changes in groundwater and/or surface water due to coal resource development. Landscape classes were used to reduce the complexity of assessing potential impacts on a large number of water-dependent assets by focusing on the hydrological drivers and interactions relevant for regional-scale assessment. Although some degree of inherent heterogeneity invariably exists, individual landscape classes are nevertheless considered by the Assessment team to share a greater level of biophysical attributes (in comparison to different landscape classes), and hence are regarded as appropriate for the regional-scale focus of the BA for the Galilee subregion.

The landscape classes provide a meaningful scale for understanding potential ecosystem impacts and communicating them through their more aggregated system-level view. The landscape classification for the Galilee subregion is described in Section 2.3.3 of companion product 2.3 (Evans et al., 2018) and the methodology that underpins it is described in companion submethodology M05 (as listed in Table 1) for developing a conceptual model of causal pathways (Henderson et al., 2016).

Potential hydrological changes were assessed by overlaying the extent of a landscape class or asset on the zone of potential hydrological change due to additional coal resource development. For the landscape classes or assets that lie wholly outside the zone, hydrological changes (and hence any potential ecosystem or asset-level impacts) are very unlikely, and are thus ruled out in terms of further analysis. Section 3.4.2 identifies landscape classes in the Galilee subregion that can be ruled out from potential impacts on this basis.

Where an asset or landscape class wholly or partially intersects the zone of potential hydrological change, there is the potential for impact. This does not necessarily mean there will be an impact, but rather, based on the magnitude of the hydrological change, the possibility of an impact cannot be ruled out and further investigation is required. The nature of the water dependency of the landscape class can also be important at this stage of the analysis. For example, if the water dependence of a landscape class relates to overbank flows to support seedling establishment, but the significant hydrological changes in the nearby stream relate only to low-flow variables (i.e. flows that are contained within the streambanks), then it may be possible to rule the landscape class out of further consideration because it is unlikely to be impacted.

Four receptor impact models were built, representing three landscape groups in the Galilee subregion (Table 8). These were used to quantify the potential impact of the predicted hydrological changes on a selected receptor impact variable within the receptor impact model (companion product 2.7 for the Galilee subregion (Ickowicz et al., 2018)). Meaningful hydrological response variables and receptor impact variables (Table 8) were elicited from experts (listed in Table 3 in companion product 2.7 for the Galilee subregion (Ickowicz et al., 2018)) during qualitative and receptor impact model workshops and subsequent correspondence. A full description of receptor impact modelling is described in companion submethodology M08 (as listed in Table 1) (Hosack et al., 2018), with its application to the Galilee subregion in companion product 2.7 (Ickowicz et al., 2018). This includes Table 4 in Section of companion product 2.7 which summarises some of the assumptions made for the receptor impact modelling, the implications of those assumptions for the results, and how those implications are acknowledged through the BA workflow and ultimately within this product. Examples of the main assumptions include the simplification of complex ecological systems, the segregation of the system into discrete classes that are assumed to respond similarly to hydrological changes, and the assumption that areas of landscapes classes remain constant over time (see Table 4 in companion product 2.7 for the Galilee subregion (Ickowicz et al., 2018) for the complete list of assumptions). The specific implications or flow-on effects of these assumptions are further explained in the respective sections for individual landscape classes in companion product 2.7 (Ickowicz et al., 2018). It is also important to note that the outputs from receptor impact modelling (which translate potential hydrological change into potential change in ecosystem indicators) are only one line of evidence used in this impact and risk analysis, and these outputs need to be considered in the context of the assumptions made and the availability and quality of local data.

Table 8 Landscape groups, receptor impact variables and relevant hydrological response variables for receptor impact modelling for the Galilee subregion

Landscape group

Receptor impact variable

Receptor impact variable description and sampling area

Hydrological response variables

Streams, GDE and Streams, non-GDE (combined)

Offadens sp. (Baetidae) (aquatic)

Density of aquatic nymphs of Offadens sp. (Baetidae) (a type of mayfly), sampled in riffles, 3 months after the wet season. Sampling is focused on a 2.0 x 0.5 m area of stream.



Streams, GDE

Percent foliage cover (terrestrial)

Target species include Eucalyptus camaldulensis and Melaleuca spp. The sample unit is a 100 m length transect along the stream reach extending from the stream channel to the top of the bank. The width is at least 10 m increasing to 15 m in areas where more than a single row of river red gum is present during the reference period. This sample frame is invariant for predictions in future periods.




Floodplain terrestrial groundwater-dependent ecosystems

Percent foliage cover (terrestrial)

Target species include Eucalyptus coolabah, E. brownii, E. populnea and Acacia cambagei. Species excluded are E. tereticornis and E. camaldulensis. The sample unit is 1 ha.



Non-floodplain, terrestrial groundwater-dependent ecosystems

Percent foliage cover non-floodplain (terrestrial)

Annual average percent foliage cover of non-floodplain tree species in a notional 50 x 50 m quadrant.



LQD = the number of days per year with low flow (<10 ML/day), averaged over a 30-year period, LME = the maximum length of spells (in days per year) with low flow, averaged over a 30-year period, dmaxRef = maximum difference in drawdown under the baseline future or under the coal resource development pathway future relative to the reference period (1983 to 2012), tmaxRef = the year that the maximum difference in drawdown occurs, across all years. tmaxRef is negative if before the end of the relevant period or positive if after the end of the relevant period. The short-term period is 2013 to 2042 and the long-term period is 2073 to 2102, EventsR2.0 = the mean annual number of events with a peak daily flow exceeding the threshold (the peak daily flow in flood events with a return period of 2.0 years as defined from modelled baseline flow in the reference period (1983 to 2012)). This metric is designed to be approximately representative of the number of overbank flow events in future 30-year periods. Each hydrological response variable is typically reported as the maximum change due to additional coal resource development.

Potential impacts as determined from this BA are reported in Section 3.4 for landscape classes and Section 3.5 for assets. Given the large number of assets, the focus of Section 3.5 is on identifying those assets that are considered to be ‘more at risk of hydrological change’. These are the assets that overlap with areas in the zone of potential hydrological change that have at least a 50% chance of a hydrological change larger than the threshold hydrological response variable values used to define the zone. Local information is necessary to improve upon the regional-scale risk predictions made by this BA at any given site.

In addition to the analysis presented in this product, impact profiles for landscape classes and assets are available at www.bioregionalassessments.gov.au. Each profile summarises the hydrological changes and potential impacts that pertain to that landscape class or asset, for example, an increase in groundwater drawdown in the ‘Floodplain terrestrial groundwater-dependent ecosystems’ landscape group in the zone of potential hydrological change. Users of the BA products can aggregate and consider potential impacts for their own scale of interest.

The BA product suite can also be used to explore the results for landscape groups and assets using the map-based BA Explorer interface at www.bioregionalassessments.gov.au/explorer/GAL/. Information management and processing

A large number of multi-dimensional and multi-scaled datasets were used in the impact and risk analysis for the Galilee subregion, including hydrological model outputs, and ecological, economic and sociocultural asset data from a range of sources. To manage these datasets and produce meaningful results, a consistent spatial framework was needed that permitted rapid spatial and temporal analyses of impacts, without compromising the resolution of the results.

The datasets for this BA were organised into an impact and risk analysis database (Bioregional Assessment Programme, Dataset 9) to enable efficient and effective data management. The purpose of the database is to produce result datasets that integrate the available modelling and other evidence across the Galilee assessment extent. The database is required to support three types of analyses:

  1. Analysis of hydrological changes
  2. Impact profiles for landscape classes
  3. Impact profiles for assets.

The results of these analyses are summarised in each of the following three main sections of this product (i.e. Sections 3.3, 3.4 and 3.5), with more detailed information available at www.bioregionalassessments.gov.au. The impact and risk analysis database is also available at data.gov.au (Bioregional Assessment Programme, Dataset 9). Displaying analysis results

As previously mentioned, the main geographic focus of the impact and risk analysis for the Galilee subregion is on the area termed the zone of potential hydrological change (see Section 3.3.1 for details regarding the development of this zone). This area is near the central-eastern boundary of the Galilee assessment extent, around the seven coal mines evaluated by the numerical hydrological modelling. The area of the Galilee zone of potential hydrological change is about 14,000 km2, which represents less than 3% of the total area of the Galilee assessment extent (about 612,000 km2). One important consequence of narrowing the spatial extent of this BA is that most of the maps presented in this product have been redesigned to zoom into the main area of interest, thereby excluding large parts of the Galilee assessment extent (Figure 17).

Figure 17

Figure 17 Comparison of map extent (yellow box) commonly used in reporting results of the Galilee impact and risk analysis with the much larger Galilee assessment extent

The Galilee zone of potential hydrological change is less than 3% of the area of the assessment extent, which represents the entire area investigated for this bioregional assessment. Consequently, most results presented on maps in the impact and risk analysis product are zoomed to this main area of interest, and exclude much of the broader Galilee assessment extent.

Data: Bioregional Assessment Programme (Dataset 9)

In addition to displaying results on various maps, this product uses two other main data and information presentation methods. The Assessment team considers these are the most appropriate means to communicate the impact and risk analysis results:

  1. Data tables
  2. Cumulative exceedance plots. Data tables

The vast amount of data produced by the impact and risk analysis database are summarised in this product in tabular form (see Section 3.3 and Section 3.4 for specific examples). The probabilistic outputs for selected hydrological response variables (output from either the groundwater or surface water models) are categorised against specified thresholds and reported for the 5th, 50th and 95th percentile results from relevant modelling runs. The thresholds are used consistently across all impact and risk products in the Bioregional Assessment Programme, and have been chosen with regard for existing impact thresholds under either Queensland or NSW legislation (such as groundwater drawdown thresholds of 0.2 m, 2 m and 5 m specified in Queensland’s Water Act 2000), or for clarity in reporting data ranges across the surface water impacts. Cumulative exceedance plots

Cumulative exceedance diagrams are another method of presenting the impact and risk analysis results in this product. Specific hydrological examples are provided in Section 3.3. Similar to the data tables, these results are also shown for the 5th, 50th and 95th percentiles to illustrate the range of predictions. The cumulative exceedance plots are particularly useful in summarising changes in various hydrological response variables for different areas or stream lengths. For example, these plots can provide a clear summary of the total area within the zone of potential hydrological change that may be subject to a certain amount of drawdown due to additional coal resource development (across the range of the probability distribution). Likewise, the total length of stream network potentially subjected to increases or decreases in the number of days of low flow or high flow (respectively) is clearly summarised using cumulative exceedance plots, as reported in Section 3.3.3. Data processing

The datasets used in the impact and risk analysis database (Bioregional Assessment Programme, Dataset 9) include the water-dependent assets, landscape classes, numerical modelling results (groundwater, surface water and receptor impact modelling), coal resource development 'footprints' and other relevant geographic information, such as the boundaries of the subregion, assessment extent and zone of potential hydrological change. All data in the impact and risk analysis database (and the results derived from it) meet the overarching BA requirements for data transparency and accessibility.

The data were structured to overcome the slow geoprocessing operations typical of complex queries of very large spatial datasets, such as those required for this BA. This structuring was achieved by:

  • loading as many attributes as possible into relational tables, including some spatial information such as area and length data
  • simplifying and partitioning the remaining spatial data using assessment units while, importantly, retaining spatial geometries below the resolution of the assessment units.

An assessment unit is a geographic area represented by a square polygon with a unique identifier. Assessment units are non-overlapping and completely cover the Galilee zone of potential hydrological change. The spatial resolution of the assessment units is closely related to that of the BA groundwater modelling and is 1 km x 1 km for the Galilee subregion (Figure 18). Assessment units were used to partition asset and landscape class spatial data for the impact analysis. The partitioned data can be combined and recombined into any aggregation supported by the conceptual modelling, causal pathways and model data.

The interpolated modelled groundwater drawdowns (see Section are at the same resolution as the assessment units and contain a single value per assessment unit. However, the surface water modelling generated results at points (model nodes). These are then extrapolated to specific reaches of the surface water network (see Section, and are mapped to assessment units. For assessment units with only a single stream reach, the assessment unit stores the information associated with this stream segment. However, where the assessment unit contains multiple stream reaches (e.g. at the confluence of two streams), it was necessary to prioritise which stream reach was used to inform the value of the assessment unit for representing the surface water modelling results. This process applied expert hydrological judgement and reasoning, and followed a general set of rules for prioritising stream reaches, including:

  • whether the modelled reaches show a hydrological change (i.e. a reach with a potential hydrological change takes priority over a reach predicted to have no significant change)
  • whether the stream reach is represented in the model (i.e. modelled reaches take priority)
  • the stream order of each reach (i.e. a higher order stream, such as a main channel, takes priority over a lower order stream, such as a tributary)
  • reach length (i.e. where two streams in an assessment unit are of equally high stream order, priority is given to the longer of the two).

To manage issues of geospatial quality in source datasets and also technology integration, the impact and risk analysis database performed a series of geospatial operations on the source data geometry. These operations are PostGIS geometry validation, 1 m or less snap-to-grid, and (in some cases) 1 cm polygon buffering. The effect of these operations on area and length calculations is considered small. In general, the larger an individual geospatial feature, the smaller the relative impact and vice versa. For features with area greater than 10 km2 and length greater than 10 km, variation from source data calculations ranges between 0.0% and 0.5%. This variation may approach 40% for smaller geospatial features (e.g. features that may be up to several square metres in area). The geospatial operations necessary for the impact and risk analysis account for all differences in length and area that may be found when comparing data stored and used within a GIS environment, with that used in the impact and risk analysis database.

Figure 18

Figure 18 Assessment units across the zone of potential hydrological change for the Galilee subregion

The inset box (a) provides an example of the interpolation approach used to allocate hydrological response variable data from surface water model nodes to adjacent surface water reaches. In this example, near the proposed Hyde Park Coal Mine, there are three surface water model nodes shown on the main stream (Bully Creek) that flows through the mining project. Surface water model interpolation upstream of node 19 was not possible due to proximity to the proposed mine site. Hence, these stream reaches are classed as ‘unquantified potential hydrological change’ for the purposes of the bioregional assessment for the Galilee subregion. Likewise, the network of smaller non-modelled streams that will be intersected by the mine pits and site infrastructure are also classed as streams with ‘unquantified potential hydrological change’. The other stream reaches shown on Bully Creek are coloured according to the model node used for the interpolation. This inset also depicts the regular 1 km x 1 km grid of assessment units for the zone.

Data: Bioregional Assessment Programme (Dataset 4, Dataset 9)

Last updated:
6 December 2018
Thumbnail of the Galilee subregion

Product Finalisation date