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  Council » Policies and Plans » Hazard and catchment management » Level of Service and Funding Policy » 17 Differential Rating Systems » 17.1 Lower Waikato Flood Protection Differential Rating System

17.1 Lower Waikato Flood Protection Differential Rating System

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Based on the cost allocations set out in sections 2.6 and 15.4 and the draft report prepared by the classifiers, the following is a summary of the proposed Lower Waikato Flood Protection Differential Rating System.

The classification is essentially an analysis of the direct benefits that the scheme works provide to the land, property and communities.

The classification was undertaken by registered valuers with experience in the classification of similar schemes.

Direct Benefits of flood protection works, as set out in the Rating Powers Act, are as follows:

  1. Reduction in the likelihood, frequency, depth and severity of flooding and erosion; and
  2. reduction in the likelihood, frequency, and extent of damage to land and improvements to the land; and
  3. improvement of drainage;
  4. the need for water management generally - in relation to the actual and potential uses of the land and by reference to the advantages accruing from the works concerned and the responsibility for their care and maintenance.

The proposed new classification would replace that put in place when the scheme was completed. The existing classification has some severe limitations and is currently used to varying degrees by the different agencies involved in the scheme.

For the purpose of the new classification, the scheme works have been broken down into three primary layers. Typically for each layer, land has then been classified within a range of up to twelve classes reflecting the differing levels of benefit received. The three primary layers are:

  1. Main Waikato River Channel Works.
  2. Community Works.
  3. Local Protection Works (Formerly the original scheme Section A, B, and D works).

The Main Channel Works are all those works undertaken within the Waikato River to maintain the hydraulic capacity and performance of the channel.

The Scheme Community Works are those that control the operation of the scheme ponding areas, i.e. Lake Waikare and the Whangamarino Wetland. The Community Works provide storage of floodwaters from local catchment areas and in large floods, from the Waikato River and greater catchment. They are so called because they involve structures which benefit the whole lower floodplain area, and do not relate to any specific local protection works. They include:

  • The Rangiriri Spillway.
  • The Te Onetea Stream sluice gate.
  • The Lake Waikare Outlet control gate.
  • The canal between the Lake Waikare outlet and the Whangamarino Wetland,
  • The Whangamarino Control Gate.

Local protection works are the stopbanks, floodgates, pump stations and channel improvements that were aimed at protecting specific local areas or compartments. These areas have all been classified on the same basis, however for the purpose of funding a further subdivision has been undertaken in to specific ‘cost centre’ areas. Within specific cost centre areas, funding will be undertaken separately, using the required mix of differential rating over the benefit area for that cost centre, plus zone, catchment and regional rate contributions. The separate cost centre areas proposed within the Local Protection Works Layer are:

  • Waikato District Rural works (Part of the original Section B works).
  • Franklin District Rural Works excluding Aka Aka. (Part of the original Section B works).
  • Aka Aka Drainage Area Works (Part of the original Section B works).
  • Managawara Valley Protection Works (The original Section D works).
  • New Works - Deroles, Lake Whangape.

The proposed Mercer West works are currently under review due to changes in spoil availability for stopbanks. Implementation of capital rating and associated local protection maintenance rating would be subject to the scope of works finally implemented.

Additionally, two separate cost centre areas are proposed within the Main Channel works Layer. These are:

  • Main Lower Waikato Floodplain.
  • Mangawara Valley.

While the primary benefit from the Main Channel works occurs in the Lower River floodplain, an additional Mangawara Valley Cost Centre has been included to recognise the fact that some limited benefit from the Main Channel works does accrue within the Mangawara Valley. The costs of the Main Channel works have been divided 85 percent to the Main Cost Centre and 15 percent to the Mangawara.

While the differentiation into layers and cost centres adds a degree of complexity to the system, it is necessary because the range of different services provided by different agencies in individual areas requires this separation.

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