Indicator description

Why is it indicative

What does the data show

Data

Acknowledgment

Indicator description

The area of land affected by or prone to water erosion.

Why is it indicative

This indicator is a direct measure of the condition.

What does the data show

The extent, severity and rate of water erosion in Tasmania have not been assessed fully, although the Grice (1995) survey indicates that about 1 million ha of land systems contained some areas of sheet and rill erosion hazard, gully erosion and/or tunnel erosion. This is the same situation as when the first State of the Environment report was published in 1996 as no additional data has been collected.

Data

• There has been no additional Statewide information gathered on the areas affected by water erosion since the previous State of the Environment report in 1997.
   


• The only systematic Statewide survey of water erosion (gully, tunnel, and sheet and rill) was conducted in 1992, which was part of the Statewide soil and land degradation assessment coordinated by Grice (1995). These assessments were conducted on private land only. However, this survey did not include any data on the area affected by streambank erosion.
   


• The maps and tables below show the results from this survey, i.e. the extent and severity of gully, tunnel, and sheet and rill erosion on private land in Tasmania.
   

Land systems containing areas of sheet and rill erosion hazard on private land in Tasmania

Class 1 nil to minor	Class 2 moderate	Class 3 severe	Class 4 very severe	Class 5 extreme
1,836,000 ha	210,500 ha	8,000 ha	6,300 ha	1,200 ha

Source: Grice (1995).

Land systems, which are affected by gully erosion on private land in Tasmania

Class 1 nil	Class 2 minor	Class 3 moderate	Class 4 severe
1,150,800 ha	673,800 ha	224,800 ha	12,600 ha

Source: Grice (1995).

Land systems containing areas of tunnel erosion on private land in Tasmania

Class 1 nil	Class 2 shallow tunnels	Class 3 deep tunnels
1,959,000 ha	76,000 ha	27,000 ha

Source: Grice (1995).

The area of land affected by all the different forms of water erosion in Tasmania, as shown in the maps and tables above, was calculated using land systems as mapping units, which provides an idea or a broad 'picture' of the extent of water erosion rather than the exact area. That is the extent of water erosion in Tasmania maybe over represented as the area was calculated using land systems as mapping units. This means that where degradation within a land system is not uniform individual components of a system were surveyed and the whole system classed at the most severe level of degradation. Also, only small areas of a land system component maybe degraded. However, the whole land system was mapped as being degraded.

Acknowledgment

State of the Environment - Tasmanian Indicator.