Wetlands

Find further information on the Conservation of Freshwater Ecosystem Values (CFEV) Program and its data at www.dpipwe.tas.gov.au/cfev.

Spatial data

TitleCFEV Wetlands

CustodianWater and Marine Resources Division, Department of Primary Industries, Parks, Water and Environment

CreatorGIS Unit, Information and Land Services Division, Department of Primary Industries and Water (DPIW)

DescriptionWetlands of Tasmania

Input data

1. Land Information System Tasmania (LIST) 1: 25 000 hydrographic theme (Subsets: wetland swamp area and wet areas, DPIW
2. Tasmanian Vegetation Map (TASVEG) data layer (Version 0.1 May 2004 (interim data set released prior to the release of TASVEG Version 1.0), DPIW

Lineage

Development of the wetland spatial data layer used the 1: 25 000 LIST Hydrology theme (subsets: wetland swamp area and wet areas) in conjunction with the TASVEG data layer (Version 0.1 May 2004 (interim data set released prior to the release of TASVEG Version 1.0). Wetland vegetation codes (As, CA, ALK, Br, BPB, BF, L, ME, Sm, Pr, Ps, Waf, Was, We, Ws) (described in Appendix 12 of the CFEV Project Technical Report) were selected from the TASVEG data layer ((DPIW 2003)). Wetlands from the LIST hydrographic data layer were initially classified as ‘undifferentiated We’ and combined with the selected TASVEG polygons using the rules outlined below. Where there was significant overlap, TASVEG polygons were given preference. After merging the two data layers, the wetlands were classified as:

1. undifferentiated (LIST ‘undifferentiated We’ + TASVEG ‘We (generic)’)
2. differentiated (all other polygons)

Wetland polygons that shared boundaries or overlapped were dissolved to form one polygon. A dominant TASVEG type was assigned to the dissolved polygon.

Rules for amalgamating TASVEG and LIST wetland polygons

The following rules were used to amalgamate the TASVEG and LIST wetland polygons. An illustration for each rule is given in Figure 1.

1. When TASVEG and LIST polygons abut each other, treat as separate polygons.
2. When TASVEG and LIST polygons overlap each other significantly, create the TASVEG polygon (1) first and then create new polygon with remaining LIST polygon (2).
3. When the LIST polygon is inside the TASVEG polygon, create polygon from TASVEG layer (1) and remove LIST polygon.
4. When TASVEG polygon and LIST polygon overlap each other slightly, create polygon from TASVEG layer (1) and remove LIST polygon.
5. When the TASVEG polygon is inside the LIST polygon (almost being the same size as TASVEG polygon), create polygon from TASVEG layer (1) and remove LIST polygon.
6. When the TASVEG polygon is inside the LIST polygon, create TASVEG polygon (1) first and then create LIST polygon with a hole in it where the TASVEG polygon was.

Figure 1. Diagrams to accompany rules for amalgamating TASVEG and LIST wetland polygons. Red = TASVEG wetland and Blue = LIST wetland.

Data limitations

Wetlands <0.5 ha that could not be assigned with an appropriate wetland vegetation type were deleted from the data set.

Date createdOctober 2004

Scale and coverage1:25 000; Statewide

References

DPIW. (2003). TASVEG 0.1 May 2003. Tasmanian Monitoring and Mapping Program. Department of Primary Industries and Water, Hobart.

Harris, S. and Kitchener, A. (2003). Tasmania's vegetation: a technical manual for TASVEG, Tasmania's vegetation map: Version 1.0. (Draft). Department of Primary Industries, Water and Environment, Hobart.