Reducing the Risk Proposed River Clearance and Maintenance
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Reducing the risk Proposed River Clearance and Maintenance Programme for the Waitotara Catchment Taranaki Regional Council Private Bag 713 Stratford February 2006 Doc# 28555-v1 Executive summary • The purpose of this document entitled Reducing the Risk –Proposed Channel Clearance and Maintenance Programme for the Waitotara Catchment is to set out a proposed river control programme to assist in addressing the effects of flooding and other storm related damage on people, their communities and the environment in the Waitotara catchment. The proposed programme is presented within the context of a range of other response options that have been or are being considered and agreed to proceed, or rejected by both the Taranaki Regional Council and South Taranaki District Council as appropriate options for integrated flood response management in the area. • As part of the reforms of the civil defence emergency management sector, central government has expressed a strong desire for a holistic approach to civil defence and emergency management. This includes: – greater focus on identifying and reducing the risks posed by hazards – integrated planning and promoting inter-agency co-ordination – promoting a risk management approach to hazards. • Flooding and other storm related damage is a major issue in the Waitotara catchment. Over the last 15 years there have been four major storm and/or flood events that have caused significant and widespread damage in the Waitotara catchment. These effects have included damage to buildings and properties, the siltation of flats after flooding, widespread slipping, channel and bank erosion and damage to the roading, telecommunication and electricity infrastructure. • This Plan details eight management options that have been considered by both the Taranaki Regional Council and South Taranaki District Council – the upgrading of flood warning systems, promoting soil conservation on farmland, the removal of part or all of the Waitotara township, additional district plan and building controls, the construction of a flood protection scheme, channel clearance and maintenance works, upgrading stormwater drainage systems and no mitigation measures. • On reviewing cause and effect issues arising from the 2004 flood event, the Taranaki Regional Council has determined that a staged programme of channel clearance and maintenance works would be beneficial in mitigating future flood damage. A works programme, including funding arrangements, is proposed and set out in section 4.3 of this document. The South Taranaki District Council is undertaking maintenance and upgrading works of the stormwater drainage system in the Waitotara township; developing a District Plan change to create a flood hazard zone for the Waitotara township; controlling new building consents through the Building Act provisions; and is currently investigating a future district-wide strategy for flood affected townships. i ii Table of contents Executive summary ...................................................................................................................i Table of contents ......................................................................................................................iii List of figures............................................................................................................................iii List of tables..............................................................................................................................iv 1. Introduction....................................................................................................................... 1 1.1 Purpose .........................................................................................................................1 1.2 Scope and structure..................................................................................................... 1 2. Background........................................................................................................................ 3 2.1 Physical characteristics and land use........................................................................ 3 2.2 People and infrastructural assets at risk .................................................................. 4 2.2.1 Population............................................................................................................ 4 2.2.2 The economy, network utilities and infrastructure ....................................... 5 2.3 History of storms and flooding ................................................................................. 6 3. Response options .............................................................................................................. 9 3.1 Upgrade flood warning systems ............................................................................... 9 3.2 Promote soil conservation and erosion control..................................................... 10 3.3 Remove all or part of the Waitotara township...................................................... 11 3.4 Planning and building controls............................................................................... 12 3.5 Flood protection scheme for the Waitotara township.......................................... 13 3.6 Channel clearance and maintenance works .......................................................... 14 3.7 Urban stormwater drainage systems...................................................................... 15 3.8 No further mitigation measures.............................................................................. 15 4. Proposed channel clearance and maintenance programme ..................................... 17 4.1 Background ................................................................................................................ 17 4.2 The Trials .................................................................................................................... 17 4.3 The proposed programme........................................................................................ 18 4.3.1 The programme................................................................................................. 18 4.3.2 Duration of the programme ............................................................................ 18 4.3.3 Implementation of the programme................................................................ 18 4.3.4 Cost of the programme .................................................................................... 21 4.4 Who benefits – who pays ......................................................................................... 21 4.5 Funding mechanisms................................................................................................ 22 4.6 Local programme ownership and advocacy ......................................................... 22 4.7 Review......................................................................................................................... 23 Appendix I: Photo record of the February 2004 storm event ........................................... 25 Appendix II: Comprehensive farm plans prepared in the Waitotara catchment (as at 30 June 2005)................................................................................................................................. 27 List of figures Figure 1: The Waitotara catchment ............................................................................................ 3 Figure 2: Network utilities and infrastructure in the Waitotara catchment ......................... 6 Figure 3: Implementation of the Waitotara River Clearance and Maintenance Programme .................................................................................................................................. 19 iii List of tables Table 1: Vegetation cover in the Waitotara Catchment........................................................... 4 iv 1. Introduction 1.1 Purpose The purpose of this document entitled the Reducing the Risk – Proposed Channel Clearance and Maintenance Control Programme is to set out for discussion a proposed catchment management programme to reduce the probability of flooding and other storm related damage in the Waitotara catchment. This document also sets out work which has been and is currently being undertaken by the South Taranaki District Council. 1.2 Scope and structure Flooding and other storm related damage is a significant and reoccurring problem in the Waitotara catchment. As part of the reforms of the civil defence emergency management sector, central government has expressed a strong desire for a holistic approach to civil defence and emergency management. This includes: ¾ greater focus on identifying and reducing the risks posed by hazards ¾ integrated planning and promoting inter-agency co-ordination ¾ promoting a risk management approach to natural hazards such as flooding and landslides. This document has been prepared for discussion purposes and sets out options and a proposal for managing the effects of flooding and other storm related damage in the Waitotara catchment through the management of land, river systems, and flood mitigation measures. This document is divided into four sections. Section 1 introduces the purpose, scope and structure of this document. Section 2 sets the context and risks of flooding and other storm related damage in the Waitotara catchment – encompassing its physical characteristics, the people and infrastructural assets at risk, and the history