Explanation

For areas with known or suspected hazards, the most effective control technique available involves the retention of Council discretion in order to avoid or mitigate hazards. Areas subject to natural hazards can be readily mapped to permit ease of reference, facilitating greater public awareness of natural hazards.

Council has already begun programmes to identify areas in the District which are subject to land instability. The land instability notation has been based on soils information and geotechnical and flooding reports for the Te Aroha township area. In order to impose controls on land subject to slippage without being unduly onerous on land not at risk, it is important that this work be continued. The use of GIS as a mapping tool will speed this identification work. Where land is identified as unstable, it is important from a public safety viewpoint to require appropriate studies and impose appropriate controls. It is the intention of the Plan that general controls on buildings will be applied through the Building Act 1991 and in addition controls on all structures and built forms within identified hazard areas will be applied using the discretionary activity status afforded by the Plan.

Large areas of impermeable surface (pavement, roofing, buildings) generate significantly more stormwater runoff than original permeable ground surfaces such as soil covered by pasture or bush. Increased runoff can boost flood loads in rivers and streams and lead to scour or erosion intensifying downstream hazard.

It is, therefore, appropriate to require technical evaluations of the impact of increased stormwater flow from larger developments such as industrial or commercial buildings, carparks or loading yards and to require increased stormwater loads to be managed or mitigated to avoid downstream effects. This will be particularly important in low lying areas already subject to flood hazard. The coverage area with impermeable surfaces of 1,000m² is similar to that applied in other regions. A range of mitigation options will need to be evaluated on a case by case basis including stormwater retention ponds, volume and velocity control devices. In general, net stormwater discharge from a site should remain largely unchanged after development takes place. This will ensure that no additional hazard is created.

The forested areas of the Kaimai Ranges and western foothills represent both a valuable resource and a potential fire threat to the residents of Matamata-Piako. The fire hazard line has been drawn around those areas which are identified as "high risk areas" within the Council's rural fire plan. The line has been drawn a standard distance of 200m from the area to be protected. The rules and methods included in this plan are intended to protect the forest resource from accidental fires caused by nearby dwellings and to provide a safety factor for homes and public buildings near forest areas should a fire occur. The methods also enable the controlling of access to high risk areas during dry periods, acknowledging that a possible cause of forest fires is uncontrolled access to these areas during these periods.

The Building Act 1991 contains a range of provisions appropriate for seismic hazard and wind hazard management in the District. To avoid confusion it is considered that the best approach with regard to an essentially undefined seismic hazard is to use the provisions of the Building Act 1991, in the interim until more accurate risk assessment data is available.

Wind zones based on accepted national standards provide the simplest technique for defining the relative degree of hazard for different geographical areas of the District. The wind hazard management and mitigation provisions of the Building Act 1991 will be relied on.

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