Abstract
The dataset was derived by the Bioregional Assessment Programme from multiple source datasets. The source datasets are identified in the Lineage field in this metadata statement. The processes undertaken to produce this derived dataset are described in the History field in this metadata statement.
Hunter Zone of Potential Hydrological change including input and derived layers.
The final Zone of Potential Hydrological Change (ZPHC) is a union of the groundwater ZPHC and suface water ZPHC, which in turn were derived from groundwater and surface water impact modelling. The groundwater component of the ZPHC is where the the probability 5% or greater of equalling or exceeding 0.2m drawdown and is derived from the 95th Quantile layer.
The surface water component of the ZoPHC is derived from the reaches that are deemed impacted from the surface water modelled (sometimes referred to as Step 1 reaches) as well as additional non modelled reaches that are deemed to be potentially impacted due to interactions with the GW drawdown layer (aka Step 2) or proposed mine operations at the surface (aka Step 3). How these are derived is expanded on in the History section of the metadata.
The SW ZoPHC is created from AU cells that intersect any of the impacted stream lines (from steps 1-3 above) as well as those which intersect GDE landscapeclass singlepart polygons withing 150m of the impacted stream lines.
Some manual post processing edits were undertaken to remove anomalous AU cells. Mostly these occurred in the Macquarie-Tuggerah region of the ZoPHC to exclude AU cells selected due to intersecting upslope rainforest and wet schlerophyll forest GDE polygons in narrow valley areas.
The dataset contains the HUN_ZoPHC_source_AU_master_20171115.shp. It is the same as the previous one except that it has the additional field "RIM_reason" which identifies an AU as to what RIM analysis is subject to (eg "forested wetlands"). As before, it also contains the input component layers that were used to define the SW ZoPHC. They being
1) the bits of SW_Modelling reaches (above) that showed modelled or assumed change plus the additional rch_200 and rch_300 reaches
2) GDEs used to identify riparian AUs not intersected by the streamlines above but to be included in the SW ZoPHC.
Importantly the ZoPHC_source_AU_master contains the reach id to which an Assessment Unit (AU) is allocated.
Important note: an AU is only allocated to a reach if it is within the SW ZoPHC
This accounts for why there are some AUs that have a modelled reach passing through them but have a NULL "allocreach" value. It is because they are not in the SW ZoPHC. This will usually be because the reach shows modelled "no change" or there is presumed no change due to the reach not being hydrologically connected to any ACRD activity. However there are some AUs that have been deemed by expert judgement to be not in the SW Zone because existing Baseline activity has nullified the potential ACRD impacts.
Dataset History
GW ZoPHC
A CON statement in ArcGIS Spatial Analyst was used to extract the area of the 95th quantile (HUN_dmax_acrd_quantile_95.asc from the input dataset) raster layer where drawdown was >= 0.2m. The resulting integer zone grid was vectorised into a shapefile. An anomalous zone on the SW boundary of the subregion that was an artefact of the modelling was deleted. The result is the GW ZoPHC
SW ZoPHC
the outputs of the processes below can be found in the "Input_Component_Layers" folder of this dataset.
Step 1
Potentially impacted reaches were extracted from HUN_SW_Modelling_InterpolatedReaches_Network_20170220_v02.shp (source dataset: HUN_SW_Modelling_Reaches_and_HRV_lookup_20170221_v02). These are line features where "SW_ZoPHC" = 'yes' or 'part'. From these extracted "impacted" reaches, the line features classified as "part" were manually edited (cut) according to the description in the HRV (Hydrological Response Variables) LUT spreadsheet (HUN_SW_Modelling_Reaches_HRV_lookup_20170221_v02.xlsx in source dataset: HUN_SW_Modelling_Reaches_and_HRV_lookup_20170221_v02). This typically involved trimming the line back only to that in or downstream of the GW ZoPHC extent. Also some "part" impacted line features were cut where they intersected existing (i.e. baseline) open cut pits (OC). These excisions were done onscreen by eye, with reference to OC pit polygons used for modelling and existing mine workings shown in Google Earth imagery. The result after this trimming of selected features is the shapefile Step_1_SW_Model_ImpactedReaches_modified_for_SWZoPHC_defiition.shp
Step 2
Streams other than "highly intermittent ephemeral" in the Hunter Perenniality layer, that where inside or downstream of the GW ZoPHC were selected and underwent the same Baseline open pit excision process as above. This became the Step_2_NonEphemeral_Streams_affected_by_GW_drawdown_modified_for_SWZoPHC_defiition.shp shapefile. Note that some streams identified by Step 2 are already described in SW model (i.e. are included in the Step 1 features)
Step 3
"highly intermittent ephemeral" streams from the Hunter Perenniality layer that were inside or downstream of ACRD open cut pits (based on the GW model ACRD OC footprint polygons) were selected. This became the Step_3_Ephemeral_Streams_crossing_ACRD_pits_modified_for_SWZoPHC_defiition.shp shapefile.
Using the three "impacted" stream layers derived above in conjunction with a singlepart shapefile, the final Zone of Potential Hydrological Change (ZPHC) is a union of the groundwater ZPHC and surface water ZPHC, which in turn were derived from groundwater and surface water impact modelling.
Dataset Citation
Bioregional Assessment Programme (2017) HUN ZoPHC and component layers 20171115. Bioregional Assessment Derived Dataset. Viewed 13 March 2019, http://data.bioregionalassessments.gov.au/dataset/d839f3b4-b6b6-438b-acc4-f909067e4135.
Dataset Ancestors
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