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Soil Stability in the Waikato Region 2007

TR 2009/24

Report: TR 2009/24

Author: A. B. Thompson, Thelton Environmental Limited

Executive summary

This report summarises data and discusses results from a survey of soil stability (intactness and disturbance) undertaken for Environment Waikato (EW) in the year 2009.  The survey has been carried out in accordance with the National Land Monitoring Forum’s procedure for point sampling.  A previous survey was conducted for the Waikato region in 2003.  Both surveys have been undertaken primarily to provide information about soil stability (intactness and disturbance) for state of environment reporting.

The monitoring was defined by the boundaries of the area that EW has statutory responsibility for.  Within this area, soil stability was assessed at 6122 sample points, distributed at 2 kilometre intervals on the map grid, using digital orthophotos taken for EW in 2007-08.  Data recorded were land use, associated vegetation, soil stability, soil disturbance (if present), and area freshly disturbed (where present).


Soil Stability in the Waikato Region 2007
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Table of contents

  Acknowledgements i
  Executive summary vii
1 Introduction 1
2 Methods 1
2.1 Background 1
2.2 Brief and specifications 2
2.3 Survey concepts and definitions 3
2.4 Description of survey methods 4
2.5 Technical conclusions 4
3 Report structure 4
3 Region wide results 5
3.1 Soil stability throughout the Waikato region, 2007 5
3.1.1 Stable surfaces 6
3.1.2 Erosion- prone surfaces 6
3.1.3 Eroded and eroding surfaces 6
3.1.4 Extensively disturbed surfaces 6
3.1.5 Unclassifiable surfaces 7
3.2 Soil disturbance throughout the Waikato region, 2007 7
3.2.1 Disturbance by land use 8
3.2.2 Disturbance by natural processes 8
3.2.3 Regional totals (land use related and natural processes) 9
3.2.4 Land uses in Waikato region 9
4 Horticulture and cropping 11
4.1 Overview 11
4.2 Soil stability 11
4.2.1 Stable surfaces 12
4.2.2 Erosion- prone surfaces 12
4.2.3 Eroded and eroding surfaces 12
4.2.4 Soil disturbance 12
4.2.5 Disturbance by land use 13
4.2.6 Disturbance by natural processes 13
4.2.7 Summary of disturbance 13
5 Dairy farms 14
5.1 Overview 14
5.2 Soil stability 14
5.2.1 Stable surfaces 14
5.2.2 Erosion- prone surfaces 14
5.2.3 Eroded and eroding surfaces 15
5.3 Soil disturbance 15
5.3.1 Disturbance by land use 16
5.3.2 Disturbance by natural processes 16
5.3.3 Summary of disturbance 16
6 Drystock farms 16
6.1 Overview 16
6.2 Soil stability 17
6.2.1 Stable surfaces 17
6.2.2 Erosion- prone surfaces 17
6.2.3 Eroded and eroding surfaces 17
6.3 Soil disturbance 18
6.3.1 Disturbance by land use 18
6.3.2 Disturbance by natural processes 19
6.3.3 Summary of disturbance 19
7 Forest plantations 19
7.1 Overview 19
7.2 Soil stability 20
7.2.1 Stable surfaces 20
7.2.2 Erosion- prone surfaces 20
7.2.3 Eroded and eroding surfaces 21
7.3 Soil disturbance 21
7.3.1 Disturbance by land use 22
7.3.2 Disturbance by natural processes 22
7.3.3 Summary of disturbance 22
8 Natural forest 22
8.1 Overview 22
8.2 Soil stability 23
8.2.1 Stable surfaces 23
8.2.2 Erosion- prone surfaces 23
8.2.3 Eroded and eroding surfaces 24
8.3 Soil disturbance 24
8.3.1 Disturbance by land use 25
8.3.2 Disturbance by natural processes 25
8.3.3 Summary of disturbance 25
9 Natural scrub 25
9.1 Overview 25
9.2 Soil stability 26
9.2.1 Stable surfaces 26
9.2.2 Erosion- prone surfaces 26
9.2.3 Eroded and eroding surfaces 26
9.3 Soil disturbance 27
9.3.1 Disturbance by land use 27
9.3.2 Disturbance by natural processes 28
9.3.3 Summary of disturbance 28
10 Exotic scrub 28
10.1 Overview 28
10.2 Soil stability 29
10.2.1 Stable surfaces 29
10.2.2 Erosion- prone surfaces 29
10.2.3 Eroded and eroding surfaces 29
10.3 Soil disturbance 30
10.3.1 Disturbance by land use 30
10.3.2 Disturbance by natural processes 31
10.3.3 Summary of disturbance 31
11 Tussock and mountain vegetation 31
11.1 Overview 31
11.2 Soil stability 32
11.2.1 Stable surfaces 32
11.2.2 Erosion- prone surfaces 32
11.2.3 Eroded and eroding surfaces 32
11.3 Soil disturbance 33
11.3.1 Disturbance by land use 33
11.3.2 Disturbance by natural processes 34
11.3.3 Summary of disturbance 34
12 Wetland and coastal vegetation 34
12.1 Overview 34
12.2 Soil stability 34
12.2.1 Stable surfaces 35
12.2.2 Erosion-prone surfaces 35
12.2.3 Eroded and eroding surfaces 35
12.3 Soil disturbance 36
12.3.1 Disturbance by land use 36
12.3.2 Disturbance by natural processes 37
12.3.3 Summary of disturbance 37
13 Summary 37
13.1 Soil stability, soil disturbance and bare soil region-wide 37
13.1.1 On stable and erosion- prone land 38
13.1.2 On eroded and eroding land 38
13.1.3 On extensively disturbed land 38
13.2 Soil disturbance region wide 39
13.3 Pressure on soil - impacts of land use 40
13.3.1 On land in rural use 40
13.3.2 On land in conservation use 41
13.3.3 On land in other use 41
13.4 Pressure on soil - impacts of natural processes 41
13.4.1 On land in rural use 42
13.4.2 On land in other use 42
  References 43
Appendix 1: Data recording codes and procedures used for Environment Waikato’s point sample 2009 44
Appendix 2 Technical conclusions 47