Central Waikato River Stability Management Strategy

This document is the Central Waikato River Stability Management Strategy, (the strategy) which has been developed through a collaborative process between Environment Waikato, Hamilton City Council, Waipa District Council, Waikato District Council, Waikato Raupatu Land Trust and Mighty River Power. These organisations have committed to continuing with the implementation of this strategy in the future.

There are a number of challenges for strategy partners who are charged with the management of the Central Waikato River including:

• balancing competing uses and values of the river
• recreation and visual amenity
• cultural and historic values
• natural hazards
• environmental quality
• high financial and environmental cost of protection works.

This document presents a management strategy to sustainably manage the stability of the Waikato River system between the dam at Karapiro and the confluence with the Waipa River at Ngaruawahia. It provides a vision for what we want the river to look like in 50 years time and actions that will guide development close to the river through appropriate design and policy to ensure that the vision is achieved.

It should be noted that there has been no public consultation in the development of this strategy. It is anticipated that the proposed vision and actions will be discussed with the community as part of the Long Term Council Community Plan processes and district plan variations. Community consultation may identify an immediate community need to undertake particular actions which may change the priority of some actions contained in this strategy.

Within 12 months of the Crown resolving the Waikato River Claim, the strategy will be reviewed for the purpose of ensuring it is aligned with the provisions of the Waikato River settlement. Waikato-Tainui’s involvement in the development of this strategy is without prejudice to its Waikato River Claim.

Environment Waikato and Territorial Local Authorities (TAs) within the study area have statutory responsibilities for river management under the Resource Management Act (1991), the Local Government Act (2002) and the Civil Defence Emergency Management Act (2002). These responsibilities include the control of the land to minimise the risk of hazards, and the avoidance and/or mitigation of the effects of
natural hazards.

Through an investigation initiated through Project Watershed into the effects of the dam at Karapiro, it was identified that degradation of the river bed was actively occurring with a predicted lowering of the river bed by 1.5m at Hamilton within the next 50 years. Removing the dams or introducing physical structures in the river to stop degradation were not considered feasible for social, economic, cultural and environmental reasons¹. Hazard lines have been identified indicating areas judged to have a high risk of bank instability². These areas have been identified to assist decision makers in planning future land use. Site specific investigations of bank slope instability will be required to
accurately define these lines. The technical reports and hazard maps which have been developed through the investigation phase of the project are listed in Appendix 1 and are available on request.

Although the investigation into the degradation of the river bed was the catalyst for developing a management strategy, it is acknowledged that there are a number of other influences on the river system which also need to be managed under an overarching river stability strategy.

The current and potential issues and challenges which may arise in the management of the Central Waikato River over the next 50 years have been identified as:

Environmental

• The river bed and water levels are lowering through a process of degradation caused by the dam at Karapiro.
• River banks in general are typically unstable for a range of technical reasons including bank slope and materials, groundwater flow, soil moisture, tree root prising and wind throw, land uses, river flow effects, vegetation cover, bank height and river bed degradation. The relative importance of each instability factor varies throughout the river reach.
• River bank protection works can detract from the natural character and amenity values of the river.

Economic

• The Waikato River is an essential source of hydropower. There is a need to recognise the presence of the hydro system and the contribution it has to regional and national social, environmental and economic wellbeing. 
• River bank protection works are very expensive and ongoing development of the riverbanks could result in substantial costs to the community.
• The effects of bank instability may threaten important infrastructure lifelines such as roads, rail and pipelines. Within the Central Zone, for example, there are 15 bridges and numerous public and private boat ramps and water and wastewater pipelines at threat.

Cultural

• Waikato-Tainui consider they have a duty to themselves and future generations to protect the Waikato River. Waikato-Tainui wish the River to be protected, and restored to its former health and strength.
• The need to be consistent with the principles of the Waikato-Tainui River Claim currently being negotiated with the Crown, being;
  • Te Mana o te Awa – The Waikato River is the ancestor of Waikato-Tainui representing the tribes mana, prestige and mauri. The Waikato River is regarded as one body and must be treated as such to ensure her mana remains intact.
  • Mana whakahaere – The claim seeks to achieve integrated management of the Waikato River through a co-management model for the purpose of enhancing and restoring the health and wellbeing of the river.
• Potential loss of significant historic heritage assets adjacent to the river from bank instability. There is little information on the location of such assets within the margins of the Mid Waikato River, which hinders their protection.

Social

• An increasing appreciation that the river, particularly in urban areas is a major amenity and river banks face increasing pressures for development.
• Erosion and bank instability may pose a risk to public safety. Communities may suffer property damage, economic disruption and risk injury or death if the erosion risk is not identified and mitigated.

“To protect the unique values and sense of place inherent to the Waikato River and its surrounds and promote long term availability of the river for all existing and potential uses consistent with the concept of sustainable management.”

This strategy vision has been developed to promote a desired outcome for this section of the river over the next 50 years and beyond. It has been based on community outcomes identified through the respective Council Long Term Council Community Plan (LTCCP) processes and also through consultation with key stakeholders. It is anticipated that the vision and associated actions in this strategy will be further refined through as a result of community responses to the various planning processes.

An environment where...

In order to achieve the social, environmental, cultural and economic objectives of this strategy, it is essential the following policies are adhered to:

Development and protection

• Natural river and riverbank processes should be allowed to occur except where essential assets require protection.
• Existing essential high-value built assets and infrastructure should be protected from riverbank instability.
• Undeveloped areas that are at risk from riverbank instability should remain free of capital intensive development so as not to increase the need for new riverbank protection works.
• Development should only occur where it does not require new structural bank protection works to be installed.
• New infrastructure or major capital works on existing infrastructure should be designed and located to take account of the long term effects of riverbed lowering and bank instability. As sites and structures are developed, maintained, retrofitted or renewed in the future, the responsible authorities will need to ensure they are appropriately protected, designed to accommodate predicted changes (e.g. height of stormwater pipes outfall, depth of bridge piles) or relocated if necessary.
• Riverbank development within the Hamilton CBD may involve structural protection works where the overall development reflects council strategies for intensification and appreciation of the river.
• Recognised sites of cultural and historical significance should be protected from riverbank instability.
• Riverbank walkways in areas of instability should be realigned, or protected if realignment is not considered appropriate.
• Remnant areas of indigenous riverbank vegetation should be retained.
• The national social and economic wellbeing derived from the hydro system should be recognised.

Protection methods

• Non-structural approaches to bank protection such as tree planting are preferable to structural approaches wherever they are effective.
• Riverbank planting should involve eco-sourced indigenous species unless effective protection requires exotic species to be used. 
• Structural protection works should follow a consistent design, take into account public access requirements, and should not detract from the natural character or amenity value of the river.
• Vegetation on the riverbanks should be managed in a way that promotes longterm bank stability.

Funding

Funding for future protection works will be in accordance with current regional and local authority policies although a review is being undertaken through 2008/09 of Project Watershed funding policies. The conclusions of the technical investigations will be assessed against the present funding policy for the zone.

The focus of Project Watershed funding is to ensure stability of the river channel and water quality. For instance, funding for flood protection will be provided where a community approach is deemed appropriate. Whereas funding will not generally be provided solely for the purpose of protecting private, Crown or local authority land such as marginal strips or reserves unless there is a clear justification and
purpose, and wider community benefits are involved. In many of these areas it may be more appropriate to allow the natural processes to occur with minimal intervention.

• Environment Waikato has a primary focus of stability of the river channel. With the predicted effects of river stability it is recognised lifelines and valuable community assets may need to be considered for support and funding.
• Asset owners are responsible for maintaining the integrity of their assets and funding will not generally be provided through Project Watershed for direct protection of site specific infrastructure assets.

It is expected that this strategy will help to guide responsible asset management practice to ensure future maintenance works are undertaken recognising the predicted long term river instability.

The management approach which will be taken, will be to adequately protect river banks, accept river changes through ongoing river processes and address the effects of lowering of water levels and bank instability. The aim is to future proof the river environment by acting now to protect existing urban and essential assets, and to adopt a passive-first approach in less developed areas. Ultimately the community faces the choice of either strongly armoured river banks at areas of risk, or the use of soft engineering and retreat back to allow a safety margin whilst allowing the continued enjoyment of the natural beauty of the river. Ultimately this strategy is a blend of these approaches reflecting the extent to which the riverbank has already been developed. A range of actions have been identified and listed in the following section.

Prioritisation of actions

An important part of implementation of these actions is programming and staging to make sure capacity and funding issues are addressed. Simple prioritisation criteria have been devised and actions have been grouped into the following time periods:

H = High - within 1 - 3 years (2008 to 2011).
M = Medium - within 3-10 years (2011 to 2018).
L = Low - beyond 10 years (2018 to 2057).
0 = Ongoing - continuing over the 50-year implementation period. The level of activity is likely reassessed over time.

It is anticipated that these actions may change as a result of the community feedback through the LTCCP process.

Table 1 - Management actions

Relevant technical documents

Smart, G.M (2003) “Degradation of the Waikato River, Karapiro to Ngaruawahia, Review of Existing Knowledge & Recommendations for Future Work”.

Smart, G.M (2005) “Analysis of Stage II Degradation Studies Waikato River, Karapiro to Ngaruawahia”.

Smart, G.M (2005) “Relative Importance of factors causing degradation in the Middle Waikato River Discussion document”.

Beca Infrastructure Ltd (2005) “Middle Waikato Bed Degradation Investigation Stages III & IV. Stage IV: Bed Degradation Management Strategy”.

Beca Infrastructure Ltd (2006) “Middle Waikato Bed Degradation Investigation Stages III & IV. Proposed Middle Waikato River Bed Degradation Management Strategy: Appendices”.

River Stability Hazard Lines : Central Waikato River Stability Management Strategy. October 2006.

URS NZ Ltd. (2007) “Waikato River Erosion Study”.

¹ Beca Infrastructure Ltd (2006) “Middle Waikato Bed Degradation Investigation Stages III & IV. Proposed Middle Waikato River Bed Degradation Management Strategy: Appendices”.
² Ibid.