State of the Environment Report title
2 0 0 4

2004 Report



Palerang

Land degradation

Indicator description

Results for this indicator are also available for  

What the results tell us for Palerang

During the current reporting period the majority of land in Palerang Council Area was under landuse types compatible with the land capability class. Salinity problems were apparent within the council area, but no new data were available on the extent of soil erosion or soil acidity over the same period.

Soil erosion at Woolcara Lane, near Captains Flat; Credit: Rosemary Purdie

Soil erosion at Woolcara Lane
near Captains Flat

Drought, wildfire, forestry activities and land uses not suited to land capabilities had the potential to cause erosion in the council area during the current period, although no data were available on their actual impact. Vegetation vigour in the council area was the lowest in November 2000 following a period of the seventh lowest recorded rainfall for Bungendore area.

Sustainability of landuse

See also: Landuse

The majority of land in Palerang Council Area was under landuse types compatible with the land capability class (see Table 1). About 2% of the council area had mapped landuses which were not suited to land capabilities and thus had the potential to cause erosion.

Of the 39% of the council area under grazing (the dominant landuse), some 96% of the land was within its capability to be used for that purpose. The remainder of the grazing lands were in areas with a high erosion risk if cleared, but may support limited clearing; the Department of Natural Resources (DNR—formerly Department of Land and Water Conservation) recommends that these areas remain timbered or revegetated in order to reduce the high risk of soil degradation.

Of the 0.2% of the council area under cropping, some 58% of the land was not suitable for regular cultivation. Poor suitability of these lands for regular cultivation may be partially due to climatic variables as well as erodibility. Potential impacts of this may include low crop yields or, in more steeply undulating terrain, erosion.

Of the 3% of the council area under rural residential uses, about 2% of the land was not within its capability to be used for that purpose. The area of these lands under land capability class VII has a high erosion risk if cleared; the Department of Natural Resources recommends that these areas remain timbered.

Of the 2% of the council area under private timber plantations, about 6% of the land was within land capability class VII. The area of these lands under land capability classes VII has a high erosion risk if cleared, and although much of the timber production forests within the state occur on these lands, they are not necessarily suited to forestry operations; the Department of Natural Resources recommends that these areas remain timbered.

Table 1: Area (ha) of landuse types within each land capability class in Palerang Council Area, 30 June 2004
LanduseLand Capability Class
Lands suitable for regular cultivationLands suitable for grazing—occasional cultivationLands suitable for grazing—no cultivationOther lands
IIIIIIIVVVIVIIVIII
Cropping865820400.2
Estimated grazing7,7496,48291,55927,28260,7815,8831,436
Horticulture20.2314
Other plantations133,0471,3626,7827490.1
Rural residential415257,2644,1163,546317
Totals (hectares)7,8787,020101,93032,78071,1546,9501,436

Source: see About the data

Types of land degradation

Erosion

The only data available on erosion extent in Palerang Council Area are derived from surveys carried out between 1985 and 1992 (see tables 2 and 3). These surveys indicated about 1,030 kilometres of gully erosion and about 380 kilometres of streambank erosion were present in the council area at that time (see Table 2), as well as extensive areas of severe to minor sheet erosion (see Table 3).

Just under 37% of the gully erosion measured between 1985 and 1992 was classed as severe to extreme, and most gullies were less than 3 metres deep (Table 2). It is considered that most erosion gullies in Australia would have formed soon after the native vegetation was removed, and although their length has since stabilised, they are continuing to contribute sediment loads to streams (Hughes and Prosser 2003), i.e. they are continuing to deepen. In NSW overall, Edwards and Zierholz (2001) estimated that accelerated erosion rates were 10–50 times the natural rates.

Table 2: Gully and streambank erosion in Palerang Council Area (prior to the current reporting period)
Erosion typeDepthKilometres
Extreme gully erosion3 to 6m deep53
1.5 to 3m deep36
less than 1.5m deep52
Extreme gully erosion total141
Severe gully erosion3 to 6m deep30
1.5 to 3m deep97
less than 1.5m deep108
Severe gully erosion total235
Moderate gully erosion3 to 6m deep13
1.5 to 3m deep69
less than 1.5m deep231
Moderate gully erosion total313
Minor gully erosion3 to 6m deep5
1.5 to 3m deep50
less than 1.5m deep285
Minor gully erosion total340
Streambank erosiongreater than 6m deep3
3 to 6m deep8
1.5 to 3m deep109
less than 1.5m deep256
Streambank erosion total376

Source: Department of Infrastructure, Planning and Natural Resources data from 1985 to 1992

Table 3: Types of erosion (excluding gully erosion) in Palerang Council Area (prior to the current reporting period)
Major erosion typeDegree and typeArea (ha)
Mass movementslump4
soil debris avalanche6
Rill erosionextreme rill erosion484
severe rill erosion57
moderate rill erosion120
minor rill erosion14
Sheet erosionextreme sheet erosion956
severe sheet erosion3,328
moderate sheet erosion31,525
minor sheet erosion215,199

Source: Department of Infrastructure, Planning and Natural Resources data from 1985 to 1992

Some erosion may have occurred within the council area during the current reporting period due to the 2002–04 droughts.

Salinity

See: | Map of salinity |

About 610 hectares of salt affected land were mapped within Palerang Council Area by DNR between 1985 and 1992, and about 21 kilometres of erosion gullies with some salting also recorded. Salinity mapping within NSW, undertaken by the DNR between 2000 and 2005, indicated Palerang Council Area had about 1,560 hectares of land affected by salinity (see Table 4). The majority of this area comprised land identified in the early phases of dryland salinity. This apparent increase in salt affected area may reflect improved data collection methods rather than a real change on the ground.

Table 4. Salinity within Palerang Council Area mapped between 2000 and 2005
Salinity typeHectares
Dryland salinity outbreak affected by severe to extreme rates of rill and sheet erosion.210
Dryland salinity outbreak affected by low to moderate levels of sheet erosion.458
Early phase of dryland salinity outbreak indicated by presence of salt tolerant plant species.873
Total Area1,560

Source: Department of Infrastructure, Planning and Natural Resources data 2000 to 2005

Soil acidity

See: | Map of acidity |

About 67% of surface soils within the Palerang Council Area were classed as strongly acid (pH 3.5-5.5) in 2002 by the Department of Land and Water Conservation (now the Department of Natural Resources) (DLWC, 2002b). These soils occur throughout the shire, apart from areas along the Shoalhaven River, Araluen Creek, Taylors Creek and Butmaroo Creek. Although many soils in high rainfall areas are naturally acid, the level of acidity in agricultural areas may be partially due to application of nitrogenous fertilizers, removal of produce, and build up of soil organic matter (Upjohn et al. 2005). In addition, about 48% of soils within the council area were classed with a high to critical risk of soil acidification (DLWC, 2002a). This included soils in agricultural areas along the Shoalhaven River and Araluen Creek that were classed as slightly acid but had a high to critical risk of soil acidification.

Impacts of soil acidity can include reduced crop yields, poor establishment of or failure of perennial pastures, permanent degradation of soil if acidity leaches to deeper soils, increase in soil erosion and siltation and recharge of aquifers leading to dryland salinity (Upjohn et al., 2005).

Causes of land degradation

Climatic conditions, natural events such as wildfires, and human activities all influence levels of land degradation. Drought conditions accompanied by overgrazing or cultivation may lead to loss of effective groundcover, leaving soil vulnerable to erosion by wind and water. Drought breaking rain may also cause erosion and can make up about 90% of the total soil loss in an area in a 20–30 year cycle (DPI 2005). Logging and fire in forested lands can significantly alter erosion rates in the short term. Atkinson (1984) measured rates up to 62 tonnes/hectare/year after bushfires, while Wallbrink et al. (2002) measured 101 tonnes/hectare/year after forest harvesting.

Drought and vegetation condition

| Change in vegetation vigour from 1997 to 2004|

The majority of Palerang Council Area falls within the Braidwood Rural Land Protection Board area. The council area suffered drought between September 2002 and June 2004 (see Table 5).

Table 5. Drought conditions for Palerang Council Area, July 2000—June 2004
MonthsSeasonal ConditionsPortion of RLPB
July 2000—June 2001SatisfactoryEntire council area
July—August 2001Satisfactory
Marginal
Majority of the council area (about 85%)
eastern part of council area (about 15%)
September 2001—July 2002SatisfactoryEntire council area
August 2002MarginalEntire council area
September 2002—November 2003In droughtEntire council area
December 2003In drought
Marginal
Majority of council area (about 95%)
Northern part of council area (about 5%)
January—June 2004In droughtEntire council area

Source: Department of Primary Industries, NSW (2006)

The vigour of vegetation in Palerang Council Area during the reporting period (see Figure 1) was lowest in mid November 2000. During the six months leading up to April 2003, about 47% of the council area experienced conditions as bad as the worst 5% of years on record with respect to vegetation vigour (i.e. a 1 in 20 year drought). In the six months leading up to October 2004, about 41% of the council area suffered these conditions. This coincides with drought declarations for the council area (see Table 5).

In the six months leading up to October 2002, about 29% of the council area experienced rainfall in the lowest 5% of years on record. Overall the 2002–03 financial year was the seventh driest 12 month period since 1890 for Bungendore, and for Braidwood was in the driest 10% of years since 1888. The lack of rainfall during this period and the resultant decline in vegetation vigour in the following months may have exacerbated land degradation within the council area.

Figure 1. Vegetation vigour index for Palerang Council Area, July 2000 to June 2004*

graph showing the change in vegetation vigour for the local government area

* Vegetation vigour index: 0 = worst; 1 = best. The index was measured three times a month (i.e. early, mid and late); Source: see About the data

Wildfire

At least 6,000 hectares of land (just over 1% of the council area) within the council area were affected by fire during the reporting period, of which about 990 hectares was wildfire and the remainder prescribed burns (very low severity). Wildfires occurred within Deua and Morton National Parks and on private lands in the east of the council area, mostly in steep wooded terrain. Although no data were available on the actual impacts of these fires on land degradation within the council area, the following points are relevant.

Forestry

About 7% of Palerang Council Area is covered by timber production forests, primarily state-owned forests. This includes about 12,000 hectares of predominantly agricultural land converted to pine plantations during the current reporting period. It is not known what impact forestry operations within the council area had on land condition during the current reporting period, but the following points are relevant.

Other causes

During the reporting period seven substances emitted to land (between July 2000 to June 2004) were reported to the National Pollutant Inventory (NPI) from one facility (Googong Water Treatment Plant). One of these substances has the ability to contaminate groundwater, five are toxic or potentially toxic to aquatic biota, two bioaccumulate in fish and shellfish and one is highly persistent in the environment. Only two of these substances were reported in all four years, one was reported in three out of four years and four were only recorded in one out of four years.

Three confirmed and eight potentially contaminated sites were listed within Palerang Council Area (see Contaminated Sites). None of these sites were remediated during the current reporting period. It is unknown what impact these areas have on land degradation.

What is being done to improve land condition?

Palerang Council Area is located within the Southern Rivers and Murrumbidgee Catchment Management Authority (CMA) areas established under the NSW Catchment Management Authorities Act 2003. Catchment blueprints were prepared by the catchment management boards which preceded the CMAs. These blueprints support the improvement of salinity, soil health and land degradation. The Murrumbidgee Catchment Blueprint (Murrumbidgee Catchment Management Board 2003), completed during the current reporting period, includes a range of management actions to restore and improve the sustainability and viability of soil and land management practices and reduce the impacts of salinity in the catchment area. The South East Catchment Blueprint (South East Catchment Management Board 2002), also completed during the current reporting period, includes a range of management actions to reduce soil loss, improve the sustainability of soil and land management practices and facilitate the identification, control and remediation of exposed acid sulfate soils in the catchment area.

An Australia-wide intergovernmental agreement on a National Action Plan for Salinity and Water Quality was introduced in December 2000. Following on from this NSW signed a bilateral agreement with the Commonwealth in May 2003 to pave the way for the development of salinity and water quality action plans in priority regions around the state. Total expenditure on land salinity and soil condition under the National Action Plan for Salinity and Water Quality within the Murrumbidgee Catchment since the commencement of funding under this program (April 2001) to March 2004 totalled about $1,760,400 for the catchment (Commonwealth of Australia 2005). A further $2,932,250 was budgeted for regional investments in land salinity and soil condition, but none of this had been spent as at March 2004. The expended funding was targeted to (Commonwealth of Australia 2005):

Total expenditure on turbidity in aquatic environments under the National Action Plan for Salinity and Water Quality within the Southern Rivers Catchment since the commencement of funding under this program (April 2001) to March 2004 totalled about $6,250 for the catchment (Commonwealth of Australia 2005). A further $65,000 was budgeted for regional investments in soil condition, but none of this had been spent as at March 2004. The expended funding was targeted to the Southern Riparian Partnership Project (Commonwealth of Australia 2005).

It is not known what proportion of the above funding was expended, or which of these activities were undertaken, within the council area.

The NSW Salinity Strategy, prepared in August 2000 (DLWC 2000), aims to provide guidance to slow the rate of increase in salinity in the period 2000–2010. Tools to do this include developing salinity targets for end of catchments and undertaking research regarding salinity processes, impacts on ecosystems, social and economic impacts and landuse systems which minimise or allow the use of affected lands (DLWC 2000). As part of this strategy, salinity hazard mapping was undertaken for the state during the current reporting period. Over the same time in the Murrumbidgee catchment, data were collected to assist in developing benchmarks for salinity control and carbon sequestration, biodiversity benchmarks were trialed, and a catchment scale salt balance model was applied to the catchment (DIPNR 2005) (see Salinity).

Community groups, council and/or other organisations undertook various projects during the reporting period that enhanced land condition in the council area; a selection of these projects is shown in Table 6. Other nationally funded activities undertaken during the reporting period in the Murrumbidgee Catchment Management Authority area (DIPNR 2004) may also have enhanced land condition in the council area.

Table 6. Projects* improving land condition in Palerang Council Area, July 2000 to June 2004
Project areaPurposeSource of grant**
Braidwood granitesRevegetation of land vulnerable to erosionNatural Heritage Trust 2001–02, Natural Heritage Trust Envirofund, 2002–03
Stony, Snowball and Big BenSalinity remediationNatural Heritage Trust, 2001–02
MerricumbeneTrack and firebreak rehabilitation following 2002 Deua bushfiresNatural Heritage Trust Envirofund, 2002–03
Environmental Trust, 2003–04

*For more information about these projects, see the NHT website and the Environmental Trust website; ** Council, community groups or other organisations may have contributed additional funding.

Other activities undertaken to enhance native vegetation and riparian condition may also help to enhance land condition.

About the data

The Department of Natural Resources (DNR—formerly Department of Land and Water Conservation) provided the following data.

The Office of the Commissioner for the Environment intersected the land capability data (provided by DNR) with the spatial landuse mapping developed for the Australian Capital Region state of the environment report to assess potential conflicts between landuse and land capability within the council area.

Normalised Difference Vegetation Index (NDVI) data were provided by Agrecon as a measure of vegetation vigour across the council area. In addition to these data, Agrecon provided data on the percentage of the council area less than the 5th percentile with respect to rainfall and NDVI in 6-month periods between April and October within the reporting period. These months were chosen to reduce any noise associated with snowfall in the winter months.

Monthly drought maps were sourced from the Department of Primary Industries (DPI—formerly Department of Agriculture) website http://www.agric.nsw.gov.au/reader/drt-area?picQuant=100. DPI prepares the drought maps from information provided by the 48 Rural Lands Protection Boards around NSW, rainfall details from the Bureau of Meteorology and reports from DPI's regional staff. Drought classification of an area takes into account a review of the area's historic rainfall records, pasture availability, climatic events such as frosts, and seasonal factors such as pasture growing seasons (DPI 2006).

The surface soil pH and soil acidification hazard mapping was provided by the Department of Natural Resources. This mapping was undertaken in 2002 by the then DLWC for the 2002 NSW State of the Environment Report. Surface soil acidity and soil acidification hazard were mapped for agricultural lands within NSW and was derived from (sometimes limited) point data in some areas and extrapolated for each soil landscape unit. Mapping scale is large and only give a broad representation of surface soil pH and soil acidification hazard at a local government area scale.

Information on pollutants was obtained from the National Pollution Inventory (NPI). NPI holds emission data reported by industrial facilities, and diffuse data collected by participating jurisdictions. Industrial facilities are required to report emissions to the NPI if they use more than a certain amount of one or more substances on the NPI reporting list, or consume more than a specified amount of fuel or electric power, or emit more than a certain amount of nitrogen or phosphorus to water. Diffuse data sources include smaller facilities that are not required to report, and mobile and non-industrial sources such as transport, domestic activities and for water catchments and land use type. The NPI website www.npi.gov.au provides further information on the techniques used to estimate emissions, data standards and how to interpret toxicity.

References

Atkinson, G (1984) Soil erosion following wildfire in a sandstone catchment, paper presented at the A.S.S.S.I. National Soils Conference, Brisbane, 13–18 May 1984, cited in Lu, H, Prosser, IP, Monn, CJ, Gallant, JC, Priestley, G and Stevenson, JG (2003) Predicting sheetwash and rill erosion over the Australian continent, Australian Journal of Soil Research Vol. 41, 1037–1062, viewed 3 May 2006, http://palaeoworks.anu.edu.au/pubs/AustJSS03.pdf.

Commonwealth of Australia (2005) National Action Plan for Salinity and Water Quality and Natural Heritage Trust Regional Programs Report 2003–04, Departments of the Environment and Heritage and Agriculture, Fisheries and Forestry, viewed 18 April 2005, http://www.nrm.gov.au/publications/regional-report/03-04/.

Cooperative Research Centre for Catchment Hydrology (2006) Bushfires and Hydrology: Background—Other Physical Changes Due to Fire, Cooperative Research Centre for Catchment Hydrology, viewed 3 May 2006, http://www.catchment.crc.org.au/bushfire/background_otherchanges.html.

CRCCH—see Cooperative Research Centre for Catchment Hydrology

Croke, J (2004) Forest Harvesting Activities and Water Quality: A New Approach to and Old Problem, in Croke, J, Takken, I and Mockler, S, Erosion in Forests: Proceedings of the Forest Workshop—March 2004, Cooperative Research Centre for Catchment Hydrology, Technical Report 04/10 December 2004, viewed 3 May 2006, http://www.catchment.crc.org.au/pdfs/technical200410.pdf.

Croke, J, Wallbrink, P, Fogarty, P, Hairsine, P, Mockler, S, McCormack, B and Brophy, J (1999) Managing Sediment Sources and Movement in Forests: the Forest Industry and Water Quality, Cooperative Research Centre for Catchment Hydrology, Industry Report 99/11, November 1999, viewed 3 May 2006, http://www.catchment.crc.org.au/pdfs/industry199911.pdf.

Department of Infrastructure, Planning and Natural Resources, NSW (2004) 2003/04 Combined NSW Catchment Management Authorities Annual Report, Volume 1: CMA Activities and Achievements, Department of Infrastructure, Planning and Natural Resources, Sydney.

Department of Infrastructure, Planning and Natural Resources, NSW (2005) Meeting the Challenge: NSW Salinity Strategy Premier's Annual Report 2003–04. NSW Department of Infrastructure, Planning and Natural Resources, viewed 12 May 2006, http://www.dlwc.nsw.gov.au/salinity/pdf/2003_2004_salinity_annual_report.pdf

Department of Land and Water Conservation, NSW (2000) Taking on the Challenge: The NSW Salinity Strategy, Department of Infrastructure, Planning and Natural Resources, viewed 4 May 2006, http://www.dlwc.nsw.gov.au/salinity/government/govt-docs.htm.

Department of Land and Water Conservation, NSW (2002a) Soil Acidification Hazard Mapping (draft), produced for the 2003 NSW State of the Environment Report, Department of Land and Water Conservation, Parramatta.

Department of Land and Water Conservation, NSW (2002b) Surface Soil Acidity Mapping (draft), produced for the 2003 NSW State of the Environment Report, Department of Land and Water Conservation, Parramatta.

Department of Primary Industries, NSW (2005) Soil Management Following Drought, Agnote DPI 355, Third Edition, Department of Primary Industries, viewed 18 April 2006, http://www.agric.nsw.gov.au/reader/pasture-crops-recovery/dpi355.htm.

Department of Primary Industries, NSW (2006) Drought maps—areas of NSW suffering drought conditions, Department of Primary Industries, viewed 8 May 2006, http://www.agric.nsw.gov.au/reader/drt-area?picQuant=100.

DIPNR—see Department of Infrastructure, Planning and Natural Resources, NSW

DLWC—see Department of Land and Water Conservation, NSW

DPI—see Department of Primary Industries, NSW

Edwards, K and Zierholz, C (2001) Soil Formation and Erosion Rates, in PEV Charman and BW Murphy (eds) Soils: Their Properties and Management, 2nd Edition, pp 39–58, Oxford University Press, Oxford, cited in Lu, H, Prosser, IP, Monn, CJ, Gallant, JC, Priestley, G and Stevenson, JG (2003) Predicting sheetwash and rill erosion over the Australian continent, Australian Journal of Soil Research Vol. 41, 1037–1062, viewed 3 May 2006, http://palaeoworks.anu.edu.au/pubs/AustJSS03.pdf.

Hughes, AO and Prosser, IP (2003) Gully and Riverbank Erosion Mapping for the Murray-Darling Basin, Technical Report 3/03, March 2003, CSIRO Land and Water, Canberra, viewed 26 April 2006, http://www.clw.csiro.au/publications/technical2003/tr3-03.pdf.

Murrumbidgee Catchment Management Board (2003) Murrumbidgee Catchment Blueprint, NSW Department of Land and Water Conservation, Sydney, viewed 25 May 2006 http://www.dlwc.nsw.gov.au/care/cmb/blueprints/pdf/murrumbidgee_blueprint.pdf.

Prosser, IP, Williams, L (1998) The effect of wildfire on runoff and erosion in native Eucalyptus forest, Hydrological Processes, 12: 251–265, cited in Cooperative Research Centre for Catchment Hydrology (2006) Bushfires and Hydrology: Background—Other Physical Changes Due to Fire, Cooperative Research Centre for Catchment Hydrology, viewed 3 May 2006, http://www.catchment.crc.org.au/bushfire/background_otherchanges.html.

SCS—see Soil Conservation Service

Soil Conservation Service (1986) The Hidden Cost of Bushfires, Department of Land and Water Conservation, viewed 3 May 2006, http://www.dlwc.nsw.gov.au/care/soil/soil_pubs/pdfs/hidden_%20cost_bf.pdf.

South East Catchment Management Board (2002) South East Catchment Blueprint – An Integrated Catchment Management Plan for the South East Catchment 2002, NSW Department of Land and Water Conservation, Sydney, viewed 5 August 2005, http://www.dlwc.nsw.gov.au/care/cmb/blueprints/pdf/south_east_blueprint.pdf.

Upjohn, B., Fenton, G. and Conyers, M. (2005) Soil Acidity and Liming Agfact AC.19 3rd Edition. NSW Department of Primary Industries, viewed 17 July 2006, http://www.agric.nsw.gov.au/reader/soil-acid/2991-soil-acidity-and-liming-.pdf

Wallbrink, PJ, Roddy, BP and Olley, JM (2002) A tracer budget quantifying soil redistribution on hillslopes after forest harvesting, Catena 47, 179–201, cited in Lu, H, Prosser, IP, Monn, CJ, Gallant, JC, Priestley, G and Stevenson, JG (2003) Predicting sheetwash and rill erosion over the Australian continent, Australian Journal of Soil Research Vol. 41, 1037–1062, viewed 3 May 2006, http://palaeoworks.anu.edu.au/pubs/AustJSS03.pdf.