FAQs about coastal hazards

We won’t be holding any public drop-in sessions for flooding and coastal hazards before the formal public consultation on the Proposed District Plan starts in October this year. When we notify the Plan, we expect to be out and about in the community to give residents an opportunity for face-to-face discussions on any of the proposed changes, including flooding related.

However, in the meantime if people have any questions that they would like to discuss with a Council planner they can come and talk to us at the Rolleston Council offices or call us on 0800 SELWYN (735 996) or email contactus@selwyn.govt.nz.

All councils in New Zealand are required to identify and manage areas that are at risk from natural hazards. Keeping our communities safe and protecting our environment is part of our job, so it’s important we do this work.

The proposed changes to how natural hazards risks are managed would only apply to new projects. If your building complied with the requirements that were in place at the time it was built, and you are not proposing to change it, then you won’t need to do anything.

It’s important to note that the new proposed provisions would only apply to those areas of your property that are identified as being at risk from flooding. The rest of the property would only have to comply with the usual zone-related rules.

Any new proposed rules will come into effect once the new Proposed District Plan is fully in place, which is expected to be in 2022. Until then, current rules for building and resource consents apply.

Finally, any new Land Information Memoranda (LIM) report for your property will now contain a note that indicates that your property may be susceptible to coastal inundation and/or erosion and/or flooding under certain circumstances. The note will also identify the latest technical information held by the Council. This is a legal requirement. Councils have to include in a LIM all relevant information they hold about a property in relation to natural hazards.

The key difference is that as a result of having to assess the district at risk from flooding in a 200-year flood event, a much bigger area of the district has now been identified as at being at risk from flooding. As for rules, in the new Proposed District Plan we are proposing to manage flood risks with similar restrictions to what’s in the current District Plan.

When investigating areas on the Selwyn coastline that could be susceptible to coastal inundation (flooding by the sea) and coastal erosion, Environment Canterbury (ECan) completed a high-level assessment. This assessment looked at current and future coastal hazards in the district and whether any more detailed assessments were necessary to inform the Proposed Selwyn District Plan.

ECan’s high-level assessment showed that the lower parts of the north Rakaia Huts settlement are susceptible to a combination of coastal hazards and river mouth hāpua (lagoon) hazards. Future sea level rise over the next 100 years is likely to increase this susceptibility. ECan then carried out a more detailed investigation for Rakaia Huts township to better identify the future coastal hazard risk and vulnerability of the area.

For more detail on the technical assessments check out the technical reports:

• ECan report R18/68: - A coastal hazard screening assessment for Selwyn District. The report broadly identifies areas potentially exposed to future coastal erosion and inundation hazards and whether any more detailed assessments were necessary to inform the Proposed Selwyn District Plan. This report can be found on ECan website.
• ECan report R19/126:- North Rakaia Huts future coastal hazard assessment. This is amore detailed investigation for Rakaia Huts township to better identify the potential extent of future coastal hazards. This report can be found on ECan website.
  

The District Plan Review has also been considering tsunami, wildfire and geotechnical hazards such as land instability, liquefaction and fault lines.

For tsunami, we are not proposing any additional rules, because the types of activities that we need to manage already require a resource consent under other rules. Instead, what we are proposing is a policy that requires evacuation procedures to be considered when the resource consent application is prepared and assessed.

On wildfire and geotechnical hazards we did some initial public consultation in late 2018. The feedback has informed the development of more detailed policies and rules, which will be consulted on once the Proposed District Plan is notified for formal public consultation later this year.

Effects of climate change on risk from natural hazards have been considered as this is something that councils must do when reviewing their district plan. When doing computer-based modelling to assess areas prone to natural hazards risk, the most recent climate change predictions were built into the models.

If you wanted to do work in an area that’s in the proposed Plains Flood Management Overlay, a site assessment would determine if, in a 1-in-500-year flood event, either:

• the water depth (measured in metres) times the water velocity (measured in metres per second) is greater than one; or
• the water depth is greater than one metre.

If yes, then your land is in a high hazard area.

If your land is within any of the Coastal Erosion Overlay, Coastal Inundation Overlay or Waimakariri Flood Management Overlay, it would automatically be in a high hazard area.

Any current or new building/resource consents aren’t affected by the proposed rules for managing flood risks until the new District Plan is fully in place. This is expected to be in mid-2022. Until then current rules for building and resource consents continue to apply.

However, for any property that has been assessed as potentially being at risk from coastal hazards, a new Land Information Memoranda (LIM) report will now contain a note that indicates that the property may be susceptible to coastal inundation and/or erosion. The note will also identify the latest technical information held by the Council. This is a legal requirement. Councils have to include in a LIM all relevant information they hold about a property in relation to natural hazards.

The Council maintains the district’s stormwater system, to manage the effects of stormwater in urban areas, through drains, swales, pipes, soakholes and treatment devices (wetlands, basins and proprietary devices) that manage run off from roof and hard-stand areas. This is managed by the Council’s Infrastructure Strategy 2018-2048 and is reviewed under the Long-Term Plan process.

The Council is active in maintaining and improving the stormwater system and is currently carrying out $1.1million worth of upgrades to the stormwater system across the district as per the 2018/28 Long Term Plan.

The stormwater system, including overland flow (run off from properties to the street) is designed to handle up to a 1 in 50 year storm event. The cost to upgrade this system to handle a one in 200 year flood event would be prohibitively expensive.

Environment Canterbury also manages flood protection for the district’s rivers, lakes and coast line through stop banks, groynes and other measures.

The proposed rules for the District Plan also aim to ensure that any new building is protected.

The mapped areas are not a record of where land has flooded in the past. They are a result of an assessment where land may flood during a large or extreme flood event in the future. We don’t have a record of any flood as large as a 200-year flood event.To date the district’s worst storm was in 2013, which was around a 70-year flood event.

We’re expecting to notify the Proposed District Plan for formal public consultation by the middle of this year. At this stage you will have the opportunity to make a submission on any of the proposed provisions, including how the flood areas are mapped.

Any submission during the formal public consultation seeking to change a mapped area will need to be supported by sufficient evidence for such a change to be accepted.

For coastal hazards the following note will be used:

The Council is undertaking a District Plan Review and through this process Council has obtained and holds information showing that this property may be susceptible to coastal inundation and/or coastal erosion. The two reports are outlined below and can be found at www.selwyn.govt.nz/districtplanreview:

• ECan report R18/68 – A coastal hazard screening assessment for Selwyn District. The report identifies rural areas that may be susceptible to coastal inundation or coastal erosion;
• ECan report R19/126 – North Rakaia Huts future coastal hazard assessment. The report identifies areas of the Rakaia Huts township that may be susceptible to coastal inundation or coastal erosion.

For more information please contact the Selwyn District Council: phone: 0800 SELWYN (735 996), email contactus@selwyn.govt.nz or visit 2 Norman Kirk Drive, Rolleston.

The Council cannot advise property owners about what effect this new flood and coastal hazard information may have on your insurance. Different insurance providers will have different policies, and we suggest you contact your insurer directly to discuss your specific policy.

We’re expecting to notify the Proposed District Plan for formal public consultation by the middle of this year. It is at this stage that you will have the opportunity to make a submission on any of the proposed provisions, including how natural hazards risk is managed.