Riparian characteristics of pastoral waterways in the Waikato region, 2002-2012

TR 2015/49
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Report: TR 2015/49

Authors: H. Jones, R. Hill, D. Borman (Waikato Regional Council) & M. Kimberley (Scion)

About this report

Riparian margins are the strips of land directly adjacent to waterways (e.g. streams or rivers) and water bodies (e.g. lakes). The careful management of these riparian margins is important in order to maintain or improve freshwater quality and ecosystems. As part of Waikato Regional Council’s State of the Environment monitoring, the regional riparian characteristics survey monitors the state of riparian fencing, vegetation, and stream-bank erosion (among other characteristics) at waterway sites on pastoral land across the Waikato region. Survey results help to gauge the impact of efforts to promote improved riparian management in the region and may be used to help inform policy development and the prioritisation of future efforts. Results of the 2012 survey, undertaken during the summer/autumn of 2012/13, are presented, and changes over the previous 5- and 10-year monitoring periods described. Data collected at 385 waterway sites across the region during the 2012 survey were analysed to provide a picture of the state of the riparian characteristics observed and compared with the data collected during previous surveys (2002 and 2007) to describe the changes in those characteristics over time. Survey results are presented for the region as a whole (i.e. region-wide), by management zone, land use (dairy and drystock), and stream order (a representation of stream size). A key finding of the report is that the amount of riparian fencing across the Waikato region has increased from 34% of bank length in the 2002 survey to 51% in the 2012 survey. The emphasis placed on improving stock exclusion on dairy farms by the Dairying and Clean Streams Accord appears to have had a positive impact on the amount of riparian fencing observed at dairy sites in the Waikato region. However, further work toward encouraging, supporting, and facilitating the fencing of unprotected stretches of waterways in pastoral land in the region is required. 

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Riparian characteristics of pastoral waterways in the Waikato region, 2002-2012 [PDF, 3.5 MB]

Contents
  List of figures iii
  Executive summary viii
1 Introduction 1
2 Methods and materials 5
2.1 Survey design 5
2.1.1 Management zones 6
2.1.2 Land use type 8
2.1.3 Stream order 8
2.2 Sample site selection and sample sizes 9
2.3 Field data collection 11
2.3.1 Approach and equipment 11
2.3.2  Characteristics observed 13
2.3.3 Post data collection: routine spatial correction and automated data extraction 16
2.4 Data analysis 17
2.4.1 Analysis of state (2012) 17
2.4.2 Analysis of change over time 20
2.4.3 Methods for the analysis and review of the survey design 21
3 Results and discussion 22
3.1 Riparian fencing 22
3.1.1 State 22
3.1.2 Change over time 26
3.1.3 Summary of key riparian fencing results 30
3.2 Stock access and exclusion 31
3.2.1 State 31
3.2.2 Analysis of Dairying and Clean Streams Accord qualifying sites 34
3.2.3 Summary of keystock access and exclusion results 36
3.3 Riparian vegetation 37
3.3.1 State 37
3.3.2 Change over  time 42
3.3.3 Summary of key riparian vegetation results 46
3.4 Riparian buffer width 47
3.4.1 State 47
3.4.2 Summary of key riparian buffer results 52
3.5 Stream crossings 53
3.5.1 State 53
3.5.2 Summary of key stream crossing results 56
3.6 Stream-bank erosion 56
3.6.1 State 56
3.6.2 Change over time 62
3.6.3 Summary of key stream-bank erosion results 66
3.7 Drivers of stream-bank erosion 67
3.7.1 Correlation analysis 67
3.7.2 Simple regression analysis 69
3.7.3 Multiple regression analysis 71
3.7.4 Summary of key drivers of stream-bank erosion results 72
3.8 Analysis and review of survey design 73
3.8.1 Effect of varying sample size 73
3.8.2 Effect of varying sampling unit length 74
3.8.3 Potential improvements in survey design efficiency 76
3.8.4 Recommendations for design of future surveys 78
3.8.5 Summary of key analysis and review of survey design results 78
4 Summary, conclusions and recommendations 80
4.1 Region-wide state and trend 80
4.2 Land use differences 81
4.3 Management zone differences 81
4.4 Stream order differences 82
4.5 Survey design review 82
  References 83
  Appendices 87
  Appendix 1 87
  Appendix 2 91
  Appendix 3 93
  Appendix 4 95
  Appendix 5 106