Volume One 11. Natural Hazards [D] Policy 11.2.7 – Where stormwater is to be discharged into a surface waterbody or drainage channel, there must be sufficient capacity within the waterbody to accommodate the likely rate of discharge without overtopping the banks or causing any scour. Where land disposal of stormwater is not a viable option, it is likely that the collected stormwater will be discharged into a surface waterbody/drainage channel. To ensure that this discharge does not cause a flooding hazard downstream, it is important that there is sufficient capacity within the waterbody/drainage channel to accommodate the discharge. If this is not the case, the discharge will cause overtopping of the banks. Breakout can also occur when the discharge velocity causes scour of the bed and/or banks of the waterbody/drainage channel. Methods of implementation The methods listed below are to be implemented by the Council unless otherwise specified. [D] 11.M.1 Zoning Zoning will be used as a means to ensure that the scale and/or intensity of residential, commercial or industrial development recognises the inherent risk of natural hazards. Environments more prone to natural hazards will not be zoned to explicitly provide for such land uses in recognition of the potential threat to life, property and infrastructure. A Floodway Zone will be used to identify river channels and land on Council-managed berms to reduce the risk of flooding on adjoining land. The use of the zone will allow the application of regional and district rules, as set out below, to avoid people undertaking activities that might impair the hydraulic efficiency of the floodway or the effectiveness of any flood defences. [R, D] 11.M.2 Overlay Areas subject to flooding and tunnel gully erosion hazards will be identified on the MEP maps through overlays. This will allow the application of regional and district rules, and other methods, (as set out below) to avoid and mitigate these natural hazards. [D] 11.M.3 Designations Floodways and floodway land will continue to be designated for river control works. This will enable the Council to undertake necessary maintenance work (where that is covered by Section 9(3) of the RMA) and to control activities on land that it does not own that might impair the functioning of the floodway. [R] 11.M.4 Regional rules Resource consent will be required to erect or place houses and other structures on land covered by Level 2 and Level 3 flood hazard overlays. This will allow the policies of this chapter to be applied to determine whether it is appropriate to establish these structures within areas subject to natural hazards. A permitted activity standard will be used to establish an appropriate setback for structures from rivers as an additional means of avoiding or mitigating flood hazards. This recognises that where there is no flood hazard overlay, there is still a risk of flooding when building in close proximity to rivers. In addition, a setback acts to maintain the integrity of the river channel and the stability of the river bank. 11 – 13