Stream bank vegetation

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Why we monitor stream bank vegetation •
Regional riparian characteristics survey •
Results - data and trends •
How we monitor •
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Why we monitor stream bank vegetation

Waikato Regional Council monitors stream bank vegetation to quantify what proportion of the region’s riparian margins requires further stream bank vegetation planting.

The demands on the region’s rivers and streams continue to increase as the result of land use intensification. The long-term management of these resources is a high priority to ensure freshwater quality and aquatic biodiversity within the Waikato region are preserved for future generations.

Riparian management techniques such as fencing, and planting of riparian zones are an effective way of improving water quality and increasing aquatic and terrestrial biodiversity.

Regional riparian characteristics survey

The regional riparian characteristics survey provides a repeatable and quantitative assessment of riparian fencing, vegetation, and stream bank erosion through pastoral land in the Waikato region. In addition to supporting catchment management zone works the survey information potentially supports our biodiversity, biosecurity, and environmental education strategies and programmes.

The survey provides a benchmark on stream bank vegetation and, through ongoing monitoring, can provide a gauge of the effectiveness of Waikato Regional Council’s riparian policies.

Read the full technical report relating to the 2022 survey

Results - data and trends

Riparian vegetation has been surveyed along 500 m lengths of waterways (430 sites were sampled in 2022) and the vegetation classified into woody and non-woody vegetation.

The stream bank vegetation indicator shows:

The amount of woody vegetation (as a proportion of bank length fenced) across the region has not changed significantly over the 2002–2022 period (26 per cent in 2002 and 27 per cent in 2022).
There was no difference in the proportion of bank length occupied by woody vegetation between dairy and drystock land uses.
The woody vegetation is predominantly comprised of woody exotic vegetation. However, the proportion of bank length with woody native vegetation has increased from 5 per cent in 2002 to 11 per cent in 2022. The non-woody vegetation is predominantly comprised of pastoral grass cover.
Survey results suggest that there is a positive association between effective fencing and woody vegetation (i.e. effectively fenced bank length has a higher proportion of woody vegetation than bank length that is not effectively fenced).

The amount of woody vegetation across the regions bank length has not changed significantly over the 2002–2022 period (26 per cent in 2002 and 27 per cent in 2022). However, over the past 5-year period (2017 – 2022), there was a significant increase in the proportion of bank length with woody vegetation driven by statistically significant increases in both native and willow species.

The long-term trend from 2002 to 2022 shows a general decrease in grass and weed species, as well as woody exotic vegetation. In contrast, there was an increase in the coverage of woody native species and flax/sedge rush, reflecting the impact of riparian restoration efforts.
The pattern of change in the proportion of bank length occupied by woody vegetation for both dairy and drystock land uses over the past twenty years was generally similar to that observed across the region as a whole.
Vegetation type is reported by catchment management zone in the graph below.

Streams in the Coromandel, Lake Taupō and Upper Waikato management zones had the highest proportions of bank length covered by woody vegetation, at 59 per cent, 48 percent and 44 per cent, respectively, with proportions being significantly greater than for other management zones.

Over the previous 20-year (2002–2022) monitoring period, a statistically significant increase in woody vegetation was observed for the Coromandel; while for other zones, no significant changes were observed. More recently, from 2017–2022, there were statistically significant increases in the proportion of bank length occupied by woody vegetation in the Central Waikato (5 per cent), Waihou-Piako (3 per cent) and West Coast (6 per cent) management zones. Changes in woody vegetation in these zones are associated primarily with increases in the amount of native and woody willow vegetation.

The Excel spreadsheet below contains the source data to this indicator's graphs and any additional data.

Download the data file
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How we monitor

Monitoring sites

Randomly selected 500 m lengths of waterway from all pastoral land were selected for the monitoring. The sites are stratified by management zones, land use, and waterway size (as measured by Strahler stream order).

Monitoring frequency

The monitoring occurs every five years.

Monitoring history

The regional riparian characteristics survey was completed for the first time in 2002. It has been repeated in 2007, 2012, 2017 and 2022.

Measurement technique

The regional riparian characteristics survey employs a sampling approach to provide scientifically robust estimates of the state of observed riparian characteristics (e.g. the proportion of bank length fenced). A sample site is an approximately 500 m long stretch of waterway in pastoral land at which the riparian characteristics (such as fencing, vegetation, and stream-bank erosion) are observed along both banks. Sites and observations are spatially referenced by GPS and the data are recorded using hand-held computers.

Data capture

The length of each sample site (approximately 500 m) is walked, adjacent to the waterway, and the riparian characteristics on both banks are observed and the data captured using a hand-held computer with built-in GPS. Changes in characteristics from those observed at the start point are recorded together with the spatial location of the change. The resulting stream segment information allows for the length and proportion of total stream length or bank length with certain characteristics (e.g. effective fencing) to be calculated.

Data storage

The raw data is stored in Excel spreadsheets and saved in Waikato Regional Council’s electronic document management system. The GPS data is stored in GIS layers.

Learn more about the Priority Catchments for Stock Exclusion GIS Layer
Statistical analysis

The raw data are collected using hand held computers with built-in GPS and transferred to Excel spreadsheets. The data held in Excel spreadsheets are imported into specialised statistical analysis software (e.g. R) for analysis.

Proportions of bank and stream length (with associated confidence intervals) were calculated, categories compared, variables correlated, and change over time determined using appropriate statistical analysis techniques.

Quality control procedures

There are no technical documents showing how the indicator data is quality assured but calibration of field observations and checking procedures for data accuracy is built into the methodology.

Data presentation

Survey results in terms of the state and trend in riparian characteristics 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). Proportions of bank length have been presented here as graphs.

Limitations

This indicator is not an actual measure of stream bank vegetation at every length of stream. It is a stream length sample method that provides estimates for management zones and the region as a whole.

More information

When this indicator is updated

The indicator is updated every five years. Data has been collected in 2002, 2007, 2012 and 2022.

Preparations for the next regional riparian characteristics survey, including any refinements to the survey method and design, will get underway in 2026/27. Data collection for the next survey is due to be undertaken during the summer/autumn period of 2027/28.

Last updated August 2025

Planting, waterways and wetland management Rivers and streams Aquatic plants and animals

Stream bank vegetation

Why we monitor stream bank vegetation

Regional riparian characteristics survey

Results - data and trends

How we monitor

Monitoring sites

Monitoring frequency

Monitoring history

Measurement technique

Data capture

Data storage

Statistical analysis

Quality control procedures

Data presentation

Limitations

More information

When this indicator is updated

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