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Report: TR 2015/49
Authors: H. Jones, M. Kimberley, R. Hill, D. Borman
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.
Riparian characteristics of pastoral waterways in the Waikato region, 2002-2012 (PDF, 3 MB)
| 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 |
