River and lake beds

6.6 Managing effects associated with the use of and disturbances to river and lake beds
Background to the issue
People and communities derive considerable economic, social and safety benefits from the use of river and lake beds. Dams and weirs are important for water supply or generating hydro-electric power, while culverts, bridges and fords are important for access purposes. River and flood control works protect people and property from the risks of flooding and erosion. Some river and lake bed uses also provide positive environmental benefits. Culverts, for example, prevent the direct passage of vehicles or stock through a river. Some structures date from early periods in Taranaki's history and may be of considerable historical interest and value.

Taranaki river and lake beds are generally in good condition. However, uses of river and lakebeds, which can range from vegetation disturbance to poorly managed gravel extraction, can cause a number of adverse environmental effects.

Some structures within river and stream channels can cause aggradation of the bed upstream and degradation of the bed downstream. Depending on the size of the structure and the stream, the impact of aggradation or degradation can be significant. Structures may also restrict water flows or change the physical characteristics of the bed causing flooding, erosion of the bed and banks, or both, This can lead to loss of habitat for plants, invertebrates and fish and impact on the natural character and amenity values of some water bodies.

Some structures such as dams, weirs and culverts can severely restrict fish migration, thereby reducing the abundance and diversity of fish species residing in upstream reaches and adversely affecting ecological and fishery values of the water body. Taranaki rivers and streams are home to at least 24 native and introduced fish species. Of the 27 native fish species in New Zealand 18 are found in Taranaki. Of these 18 native fish, 15 are diadromous, which means they have a marine or estuarine stage in their life cycle, and must therefore migrate to and from the sea. Introduced fish species such as brown and rainbow trout populations also benefit from unrestricted access to spawning and habitat areas in the upper reaches of streams and in tributaries.

Poorly managed gravel extraction from river and lake beds has particularly significant adverse environmental effects.

The significant issues in relation to managing the effects associated with the use of and disturbances to river and lakebeds are:

Objective

RLB OBJECTIVE 1

To enable appropriate use of and disturbance within river and lake beds in Taranaki while avoiding, mitigating or remedying any adverse effects of activities on the environment.

Policies
Adverse effects of the use of and disturbance to river and lake beds

RLB POLICY 1  

Gravel extraction

RLB POLICY 2  

Unused structures

RLB POLICY 3  

Explanation of the policies

Policy 1 sets out those adverse effects to be managed when making resource management decisions in relation to disturbances and the use of new and existing structures within river and lakebeds. Policy 1 requires adverse effects to be avoided, remedied or mitigated as far as practicable. This recognises that it may not always be possible to completely avoid, remedy or mitigate all adverse effects of the use of and disturbance to river and lake beds. However, avoiding, remedying or mitigating adverse environmental effects as far as practicable does not necessarily mean that any use and development of resources that avoids, remedies or mitigates adverse environmental effects as far as practicable, will be acceptable - adverse environmental effects must be managed in a way that gives effect to the Act's sustainable management purpose. For example, the functional operational requirements of network utilities or other critical infrastructure may have some minor or other adverse effects that cannot be fully avoided, remedied or mitigated but which are acceptable in the context of the overall sustainable management purpose of the Act.

Gravel extraction directly from river beds can have significant adverse effects on water quality, aquatic life and channel morphology. In Taranaki, extraction of aggregate from river and lake beds is generally restricted to that required for river and flood control purposes. This is because of the observed effects of past over-extraction which has caused severe river bed and bank erosion and because the rate of recovery is slow. Policy 2 has been adopted to ensure that the adverse effects of aggregate extraction from river and lake beds are avoided, remedied or mitigated. The primary means of doing this will be through a regional plan or plans.

Policy 3 recognises that there are a number of structures in river and lake beds, in particular weirs, that are no longer in use and currently restrict fish movement, or cause flooding and erosion. The intention is to promote the removal or decommissioning of such structures where it is appropriate to do so. The circumstances under which a structure is removed will be considered on a case-by-case basis. The destruction of historic structures will be carefully considered and alternatives considered. Where destruction or demolition is unavoidable the structure should be recorded prior to destruction. If the retention of a structure is considered desirable, then the circumstances, including responsibility for the structure, its maintenance and the provision of fish passage, will be determined and agreed on a case-by-case basis.

Related policies

Policies 1, 3 and 4 of Section 6.1 [Surface water allocation]; Policies 3 and 4 of Section 6.2 [Surface water quality]; Policy 2 of Section 9.1 [Indigenous biodiversity]; Policies 2 and 3 of Section 11 [Natural hazards]; all the policies in Section 10.1 [Outstanding natural features and landscapes]; Section 10.3 [Amenity values]; Section 13 [Minerals]; and Section 16 [Issues of significance to iwi].

Methods of implementation

The Taranaki Regional Council will:

Principal reasons for adopting the objective, policies and methods

The Taranaki Regional Council has responsibilities under the Resource Management Act for managing the effects associated with the use of river and lake beds. It also has responsibilities under the Building Act 2004 in relation to dams.

The objective, policies and methods of implementation establish a policy framework for managing adverse environmental effects associated with the use of river and lake beds. Their aim is to maintain the general good condition of Taranaki's river and lake beds.

The policies and methods focus on regulatory methods (complemented by a mix of non-regulatory methods). Regulation, through the inclusion of rules in the Regional Fresh Water Plan for Taranaki and conditions on resource consents relating to the siting and maintenance of river and lake bed structures and the excavation of the bed, is a simple, efficient and effective method of controlling adverse effects associated with the use of river and lake beds. Other methods such as financial incentives are necessary to promote works to remove historical fish barriers, while information provision will also assist in achieving the objective. Together, these methods are considered to be appropriate having regard to their efficiency and effectiveness and their benefits and costs.

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