3.2 Significant Issues of the District Print E-mail

3.2.1 Natural Hazards

  • The District is subject to a wide range of natural hazards and there have been several significant natural events in recorded history which have caused loss of life, damage to property and environmental damage.

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  • A considerable amount of effort has been put into remedying flood hazard and in general, the flood protection schemes along major rivers within the District provide a high level of protection. However, stopbank breaches or overtopping still present a significant hazard in the rural areas.

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  • Hazards from slips, landslides and erosion are important concerns in the hill country of the District, particularly on the steep slopes of Mt Te Aroha and along the Kaimai Range. Erosion along stream and river margins also needs to be addressed. Peat soils have been identified due to the subsidence that occurs and the fire and flood risks associated with them.

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  • Forest fire is a natural phenomena with the potential hazard greatly exacerbated by human settlement patterns and activities. In particular, hazard would significantly increase if intensified development is permitted in forested hill country areas, particularly the Kaimai Range.

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  • Wind hazard is a particular problem in areas adjacent to the Kaimai Ranges and in known wind tunnelling areas. Wind zones can be identified, with building standards and locations controlled according to the predicted level of risk.

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  • Earthquake and volcanic hazards are known to affect the District, however, at present the understanding of the extent, severity or location of these risks is poor. Further work is warranted in this area to clarify the extent of risks. However, in the interim, it is possible to identify suspected higher risk areas along fault lines or on unconsolidated ground, where a precautionary approach to development is warranted.

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  • The District Plan implements rules to avoid or mitigate the effects of natural hazards in line with the Regional Policy statement.


3.2.2 NATURAL HAZARDS
Outcome Sought
(Objectives)		 Solutions
(Policies)		 Implementation
(Methods)
Refer to the following sets of controls and reasons for chosen methods		 Explanations and Reasons
for Objectives and Policies
1. FLOODING
O1 To minimise the risks of flooding affecting people and property in the District. P1 To ensure that all future development does not increase the flood risk for existing buildings and activities. The Resource Management Act obliges Council to address the cause and effects of flooding within the District and avoid, remedy or mitigate the hazards.

Policy P1 seeks to minimise the cumulative effects of increased flood loads.

Policies P2-P4 seek to avoid additional hazards by directing development away from known flood areas and providing pathways and ponding areas for flood waters which avoid potential personal and property damage.

Policy SP1 recognises that vegetation retention in catchment areas is a proven technique for reducing rural runoff. By providing practical incentives for bush retention, land practices which contribute to hazards can be avoided.
P2 To avoid building development below a known risk factor of 1% annual return flood levels.
P3 To ensure new developments and subdivision take cognisance of overland flow paths in their design to avoid adverse effects.
P4 To utilise public open space as natural floodways and ponding areas where this does not adversely affect protected natural environments and heritage features.
SP1 To provide incentives to promote replanting and bush retention in catchment headwaters.
ANTICIPATED ENVIRONMENTAL RESULTS
  1. Negligible additional runoff from new development [typical performance measure: runoff calculations pre and post development should be similar]
  2. Concentration of building development above a 1% flood level risk [typical performance measure: building permits check]
  3. Establishment of identified flooding and ponding areas within public open space
  4. Increase in extent of catchment headwater vegetation cover
  5. Negligible net increase in stormwater loads generated by development in flood prone areas.
2. FIRE HAZARD
O1 To minimise fire hazard for people and property in the District. P1 To avoid new dwellings being erected in high risk bush and forest areas of the District. The Resource Management Act obliges Council to address the cause and effects of natural hazards and avoid, remedy or mitigate the hazards.

Forest fire is a natural phenomena with the degree of hazard being significantly increased by human activities. Objective O1 and Policies P1 and SP1 seek to avoid exacerbation of the natural hazard by directing development elsewhere and imposing public access restrictions as necessary. The policies also recognise that forest fire would have significant negative multiplier effects in terms of increased runoff, erosion and flooding hazard.
SP1 To ensure that rural fire and emergency services are adequately resourced.
3. WIND HAZARD
O1 To minimise wind hazards for people and property in the District P1 To avoid new dwellings being erected in known, specific design wind risk areas such as exposed ridges or sites subject to known wind tunnelling effects. Objective O1 and Policies P1 and P2 recognise that some parts of the District are subject to particular wind hazard created by topographical features or particular weather phenomena. The prudent response for avoiding wind hazard is to avoid development in high risk areas and control building standards as necessary elsewhere.
P2 To manage activities so as to avoid increasing wind erosion or hazard.
ANTICIPATED ENVIRONMENTAL RESULTS
  1. Concentration of building development away from high fire and wind hazard areas such as bush tracts, forested hill country and exposed ridges.
  2. No increase in the net cost of damage to persons and property through incidence of forest fire or severe wind events.
  3. No new habitable development in known high flood, wind, forest fire or land stability risk areas where mitigation cannot be readily or economically achieved.
4 LAND MOVEMENT
O1 To minimise hazards for people and property caused by erosion, slipping, slumping and land instability. P1 To ensure that future development does not aggravate instability or erosion problems. The Resource Management Act obliges Council to address the cause and effects of land movement hazard within the District and avoid, remedy or mitigate the hazard.

 

The objectives and policies recognise that a variety of land movement hazards exist within the District.

 

The most effective management technique available is to avoid development in high risk areas completely. High risk areas can be effectively replanted or allowed to revert to bush with additional amenity and environmental benefits.

 

Where avoidance is not possible or practicable, specific geotechnical investigations are warranted in suspected risk areas.
P2 To avoid development in areas subject to high risk of land movement.
SP1 To encourage WRC to provide incentives for bush retention and replanting of steep land and alongside erosion prone stream and river margins.
SP2 To encourage the retirement of high risk land to regeneration by covenant protection, public purchase and subdivision where feasible.
ANTICIPATED ENVIRONMENTAL RESULTS
  1. Concentration of building development away from high land movement hazard areas such as steep exposed land, soft sediments and along eroding waterway margins.
  2. No increase in the nett cost of damage to persons and property through incidence of land movement.
  3. Increase in extent of bush regeneration and planting on erosion prone land.
  4. Increased awareness of the extent of earthquake and volcanic hazard affecting the District.
5. EARTHQUAKE HAZARD
O1 To minimise the risks of earthquakes affecting people and property in the District as far as practicable. P1 To take a precautionary approach to development in suspected risk areas until further information on the extent and nature of earthquake risk becomes available. Parts of the District are expected to be subject to particular earthquake risks. Volcanic hazards from several parts of the central North Island also need to be considered. These are natural phenomena and research is not sufficiently advanced to permit detailed land use management and planning controls to be implemented to mitigate against the risk of an earthquake or volcanic event. In any case it will never be possible to completely avoid the effects of a major event.

Accordingly it is appropriate that Council adopts a precautionary approach to development in suspected risk areas near fault lines or on unconsolidated ground until further work to quantify the extent of hazard is completed. Council should also support the various agency initiatives taking place to gain a better understanding of the hazard in this regard.
SP1 To support initiatives aimed at designing and establishing public works and infrastructure which is more earthquake resistant.
SP2 To support initiatives for improved earthquake prediction and monitoring at district, regional and national levels.
ANTICIPATED ENVIRONMENTAL RESULTS
  1. Increased awareness of the extent of earthquake and volcanic hazard affecting the District.

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