Target Land

"TARGET LAND" is a mechanism enabling:

  • identification of land most in need of erosion control treatment.
  • a tool to rank tenders.

Labelling the Land

Land use capability (LUC) units are used to classify the land. An LUC rating is an assessment of:

  • rock type - mainly mudstone, argillite and grewacke in Gisborne East Coast;
  • soil;
  • slope, - has groupings a-h where a is 0-3 degrees and h is > 42 degrees;
  • present erosion severity;
  • vegetation - there are five broad classes: grass, crops, scrub, forest and herbaceous;
  • climate - broad factors are recognised such as at higher elevations cooler growing conditions prevail, rainfall generally exceeds 1800 mm/yr, soils are more strongly leached and important nutrients are less freely available;
  • past land use;
  • erosion potential.

and the ability of these to provide sustainable agricultural production.

The individual LUC units are divided into eight broad classes (I-VIII) expressing the total degree of limitation to sustained use. Class I has negligible limitations (such as the Poverty Bay Flats) and Class VIII has extreme limitations (such as the Tarndale Slip).

Each Class is sub-divided expressing the dominant type of limitation on sustainable use. There are four sub-class limitations:

  1. e - erosion
  2. w - wetness
  3. s - soils
  4. c - climate

Prevailing on the East Coast, the dominant type of limitation to land sustaining agricultural production is erosion.

Finally, there is most detailed category the unit. The unit defines the assemblage of physical factors. Specifically, a LUC unit groups land that "responds similarly to the same management; adapts to the same kinds of crops, pasture or forest species; requires the same kind and intensity of soil conservation and other land management measures; yields to similar potentials"

LUC unit groups

Land use capability units are unique to their region. For example VIe2 in the Waikato region is specific to that region and differs from VIe2 in the Gisborne-East Coast region.

Land use capability units are grouped into three categories and further divided into sub-categories.

Category Sub-Category LUC Unit
1 a All of Class I, Class II, and Class III
1 b All of Class IV, Class V, and Class VI
2 a & b All remaining Class VII
3 a VIIe15, VIIe16, VIIe17,
3 b VIIe18, VIIe21, VIIe23, VIIe25
3 c VIIe19, VIIe22, VIIe24
4   All Class VIII

History of "Target Land"

In 1992 there was no targeting mechanism for the ECFP. Grants were paid on all Class VII land content in accepted tenders.

Following the inaugural year of the ECFP, it was accepted that with no targeting mechanism land that could be used sustainably in agriculture might go into trees under the ECFP, which was not an objective. It was, therefore, that in 1993 "Target Land" was introduced to focus the erosion control treatments primarily on land that could not be sustainably utilised in agriculture.

From 1993 to 1999 the "Target Land" was classified as severely eroding category two land and category three land.

Nineteen ninety-nine saw the completion of the review of the ECFP. One of the outcomes of the review was to re-classify "Target Land". Today "Target Land" is category 3b and 3c land and some category four land that does not have a closed canopy cover.

Target Land

Unit Predominant Erosion Unit Description
VIIe18 Earthflow Rolling to strongly rolling* slopes on crushed argillite and sheared mixed lithologies where rainfall is >2000mm, and with a potential for very severe earthflow erosion (mainly north-west of the Waiapu River valley). At larger scales (1-2ha) the unit is characterised by poorly drained broken/hummocky ground with active/fresh shear lines along the boundary of more relatively stable land, and where pastures are modified by dense rush vegetation. This unit isn't to be mistaken with wet boggy springs/patches that exist simply due to topographic position.
VIIe19 Earthflow This unit is similar to VIIe18, on crushed argillite and sheared mixed lithologies, except that it is not restricted to areas where annual rainfall is >2000mm. This unit has slightly steeper slopes, and have more pronounced fully erosion, where the gullies are more severe the VIIe24 unit is used.
VIIe21 Gully and soil slip Strongly rolling to moderately steep slopes on unstable frittered (so called 'loose jointed') mudstone hill country. This unit is characterised by an eroding watercourse destabilising steepened sides causing soil slips and some earthflows along the gully edge.
VIIe22 Gully Moderately steep to very steep slopes on crushed greywacke, mainly in the Raukumara Range and foothills. This unit is characterised by long slopes, closely dissected by quite shallow gullies, with associated earthflows and slumps. Earthflows become important where annual rainfall is >2000mm.
VIIe23 Soil Slip, Gully Steep to very steep slopes, in bedded, frittered, or massive mudstone hill country that is mostly severely eroded by numerous slips. These have largely coalesced (joined together) to expose considerable areas of bare ground, sometimes forming very steep-sided gullies with eroding channels at their base.
VIIe24 Gully Steep to moderately steep slopes in mainly crushed argillite hill country, usually with actively eroding amphitheatre-like (large) gullies. Use VIIIe9 where the entire area of the fully form is without associated uneroded hill country.
VIIe25 Earthflow Strongly rolling to moderately steep slopes in bentonite hill country. This unit occurs in 'melange zones', found between boundaries of different major rock types. This unit is characterised by very poorly drained soils and slopes with creeping earthflows and slumps.
VIIIe3-9   These units are recognised as having potential for very severe to extreme erosion, e.g., VIIIe9 is recorded in the Tarndale slip, Bartons Gully (Wairongomai) etc. they also include very steep to precipitous slopes in gorges or riverside cliffs, and very steep to precipitous slopes on mountain land.

Source: Table and photos as courtesy of the Gisborne District Council, Soil Conservation Section, Conservation Quorum Spring 2000.

 

Last Updated: 13 January 2011

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