What a winter in the Waimakariri!
Waimakariri District Council media release: 7th September 2022
We’re now in Spring and with the beginning of the new season we want to take time to reflect on what has been a very eventful winter of record setting weather.
Council has been busy cleaning up after the extreme weather events of the past couple of months and we are looking at ways we can better prepare for these events as well as how we can help you to better prepare for them too.
We had the wettest July on record
We all know that July was a wet month – we saw four times more rain in July that the average for this time of the year. The final band of rain on Thursday 30 July plunged Canterbury into the wettest July on record.
In the Waimakariri District, forecasts warned us of up to 70mm of rain to fall over the two days between Monday 25th July and Tuesday 26th July. The average rainfall across the District that actually occurred was 50 to 150mm - depending on the location.
Across the District there were reports of surface flooding on roads, drains being near capacity and a small number of properties had flood waters enter their homes.
When the Council gets heavy rain warnings, we aim to give people as much time as possible to prepare and we provide guidance on ways to do this.
Rain itself is expected and manageable – especially during winter - but during prolonged heavy rainfall it's a trickier hazard to manage and requires everyone to take precautions.
This is because the flooding that occurs is dependent on more factors than just the amount of rainfall itself. Some of these include the direction and duration of the storm, blockages from debris and leaf fall, preceding rainfall, soil saturation and groundwater levels, river levels, tree fall, bank slips, tides (considering that all streams and rivers go out to sea) and storm water surges.
What’s normal rainfall and what’s not?
After a month of heavy rain, surface flooding should be expected.
Surface flooding is more common when the ground becomes saturated. There will always be pockets of land where water can’t drain away, it backs up and sits.
Most people will see this occur on some road sides and even some low-lying properties will have their own spots where water regularly pools.
These are normal channels for rainwater and should be expected.
Flooding becomes a problem however, when it looks like it will make its way inside buildings and homes. It is important to remember roads are designed to carry flood flow and ponding and surface water should be expected on roads during storm events. Drivers should be extra vigilant especially on rural roads and drive to the conditions or avoid travel during these extreme events.
It is also natural and expected that streams and rivers will flood beyond their banks during these events. Our District is built on a flood plain and flooding of land and roads should be expected and we should all be prepared for future flooding events.
What you can do to prepare for extreme weather
The rain on the 25 and 26 July came hot on the heels of a heavy rain event from the week prior. We still had quite saturated ground and this exacerbated issues.
When an emergency happens, Civil Defence, emergency services and Council staff will be busy helping people who need them the most.
This is why it’s important that we all take personal precautions with regards to our own safety and the safety of our homes and families.
The first thing to do is get to know the potential hazards in your area of the Waimakariri District and how they could affect you.
This can include thinking about tsunami surge, flooding, landslides, storms etc.
A great place to start is the Natural Hazards map of the District Plan.
Before a weather event, it’s also important to discuss and plan with your family, friends and workplace about how you will respond.
Civil Defence has a great website full of resources to help you do this.
If it’s all a bit late for that, some of the basic steps people can take to minimise flood risk on their properties include, cleaning out gutters and drains and preparing sandbags if you know your home is prone to flooding or if you live in low lying areas.
Make sure you stay home in adverse conditions where possible. But if you need to travel, always drive to the conditions and expect surface flooding. Assume any flood water is deeper than it looks.
If your property is likely to be at risk of water getting inside or if you’re feeling unsafe you can choose to self-evacuate and stay with friends and family. If water ever starts to come into your house phone 111.
What the Council does before and during wild weather
Before any large rain event Council staff and contractors travel the District ensuring our infrastructure is in great working condition and best placed to deal with the hazard. We deploy pumps in some urban areas known to flood and have sucker trucks on standby to relieve overloaded sewers.
During an extreme weather or natural disaster Council’s Civil Defence team opens an Emergency Operations Centre (EOC), Council Chambers become the hub.
This is where decisions are made about how to respond to the risks and information is shared with emergency services and residents. Council staff step into new roles in an EOC, often working throughout the night, gathering intel, looking after operational requirements such as surveying our roads and monitoring rivers, providing support to residents in need and coordinating with emergency services.
At the peak of the July weather events, Council received more than 1650 calls resulting in 600 requests for support or additional infrastructure.
Although we try, it is impossible to get someone to every single service request on the night. That is why, with a triage system in place we can respond first to where we are needed most and work our way down.
Our Civil Defence team and Council staff work through these events to ensure our infrastructure is functioning, any issues are identified, and signage is up in busy areas where extreme caution is required – all so any risks to residents is minimised where possible. It is important to be aware that all roads can be subject to flooding and that we do not put signs up everywhere it floods, drivers should expect flooding and potholes on roads during and after storm events and drive accordingly.
In the aftermath of July’s weather event Council staff have now turned their attention to processing the 685 drainage and 130 sewer service requests which involve on-site visits, discussion with property owners, looking at Council infrastructure and putting in place improvements where possible.
What happens afterwards
This latest month of heavy rain comes on the back of another couple of events. The 805 requests for service that arose from the July event are added to the total tally of about 1400 under investigation from prior events in May 2021, December 2021 and February 2022.
The Council had established a Flood Team to work through these requests. Based on the scale of additional service requests from July, the team has been expanded and will continue for longer. It is anticipated that it will take the team at least 6 months to work through these investigations. Normally people can expect a response to service request from council staff within weeks of them contacting us. At the moment, depending on the prioritisation of the issue, it may be several months before staff can meet on site with property owners as part of our investigations.
Many requests involves on-site visits, discussion with property owners, looking at Council infrastructure and putting in place fixes, or improvements where possible. While every attempt is made to improve drainage where possible, events of this nature can cause major damage which can take months to implement upgrades. Also in some situations the issues identified may not lead to any actual work by Council, however we can provide some advice to property owners regarding the nature of flooding in that area. Many of the issues identified will eventually be prioritised and put into the Council’s Long Term Plan for improvements across the District.
Please remember to let us know of any issues, problems and damage that occurs as soon as possible. We’re here to help and can only look into problems we know about. Your experience and records from wet weather and storms are important to us in helping understand the causes and extent of drainage and flooding issues in specific areas.