2015 FLOODS - LOOKING BACK

In June last year communities in the Horizons Region faced widespread flooding, causing damage and disruption for many in the days, weeks and months to come. 

Perhaps hardest hit was the community of Whanganui. The lower reaches of the Whanganui catchment experienced a large amount of rainfall over the duration of the event, compounded by further heavy rainfall in the lower catchment toward the end of the storm. In Wanganui, at it’s peak more than 5,150 cumecs (cubic metres per second) of water flowed down the river, estimated to be a 1 in 130 year flood event, the largest on record.  Also within the Whanganui District, communities along the Whangaehu River experienced considerable flooding with a 1 in 120 year event.

The impact on our Region has been significant, with an estimated recovery cost of $120 million, not including the cost to the rural sector. Between 350,000 and 400,000 hectares of land were subjected to high intensity rainfall and over 2000 slips recorded on roads alone.

For the Regional Council the damage to assets was on a comparatively smaller scale but not insignificant. Stopbanks along Anzac Parade/Kowhai Park in Wanganui, scheme works along the Rangitikei

Above: Anzac Parade, Wanganui, June 2015

River and a rainfall recording installation on the Whangaehu Catchment were all damaged, with the damage bill for Horizons River Management infrastructure totaling just over $4 million.

Over the past year Horizons have been assessing the damage, taking stock of information systems and identifying ways to continually improve the level of information made available to the community. This edition of Across the Region looks at some of the work that has been done since June 2015.

2015 FLOODS - ONE YEAR ON

The June 2015 floods provided a true test for Horizons scheme assets, measuring sites, communication systems and staff. It had been just over ten years since the floods of February 2004 devastated the Region and the June event provided an opportunity to see if the work that has been done over the intervening period could stand up to a major event.

Improving public information

When it comes to capturing river level information, resilience of the measuring sites and reliable communication systems are key. Since 2004, Horizons measuring sites and communication systems have been upgraded to ensure better flood modelling information based on the data collected. 

In June last year Horizons recording sites stood up to the storm battering with only one recording site washed out and four other sites suffering damage. All of these sites are now repaired. 

Horizons new website now also provides the opportunity for the community to access river level forecasting information. This is something which could be extremely 

Above: Repairing tower at Manga-atua at Hopelands Road hydro site

helpful in conjunction with the automated warning system for river users and property owners to prepare for increasing river heights in periods of heavy rainfall.

Flood plain modelling information for the Whanganui, Rangitikei and Manawatu Rivers is now also available for public to view on the Horizons website. This information provides an indication of areas that may get wet due to flood water from major water courses but does not take into account surface flooding from storm water or other localised effects. While the modelling information provides an indicator for property owners it is important to remember that just because it is not modelled does not mean that it is high and dry.

There are also six more webcams on the Horizons website at various locations around the Region. These webcams allow people to see what is happening on their rivers in real time. 

2015 FLOODS - ONE YEAR ON

Protecting our communities

Over the past year Horizons engineers have been assessing the effects of the flood in order to understand what happened and how to best plan for the future.

In Wanganui, a technical report carried out by Horizons engineers and available here, found the size of the June event to be equivalent to a 1 in 130 year flood, with a peak flow of 5,150 cumecs (cubic metres per second), making it one of the biggest flood events ever experienced in the Wanganui urban area. 

Furthermore, a cross section survey of the Whanganui River, carried out late last year, has also been used to recalibrate the flood model for Whanganui. The report found that although sediment has visibly accumulated in some places the overall effect is not significant and the river can convey the same amount (or slightly more in some places) of water as it did when last surveyed in 1995. This means that sediment build-ups did not worsen flood levels.

Consultation with the community on future flood protection options for the Whanganui River is needed but requires more work to determine what an increased standard of flood protection might look like and what it would cost. This is expected to take place early next year. However, Horizons wish the community to know they will provide guidance as requested and view protecting people's safety and livelihoods a priority.

Above: Installing rope and rail groynes, Rangitikei River

Formal public consultation for the Matarawa Scheme is also scheduled to be held over the next year. In June 2015 the design capacity of the scheme was substantially exceeded, which led to flooding of properties in Wanganui East. Horizons will be looking for feedback from the Whanganui East community on whether the Matarawa Scheme should maintain the lower reach of the Matarawa Stream through urban Whanganui, requiring a part of the Wanganui East community to pay targeted Matarawa Scheme rates.

The Tutaenui Scheme was also reasonably affected with most dams overtopping. An audit of the scheme is currently being carried out and the current levels of service considered. Once the audit is completed Horizons staff look forward to having detailed conversations with the community on future plans for the scheme.

The Rangitikei Scheme suffered the most significant damage in June 2015, with costs close to $1.9 million. Horizons have recently put forward a claim to the Ministry of Civil Defence and Emergency Management to cover a large portion of these costs. This event and its effects have also prompted Horizons to consider the viability of the Scheme in its current form and will be going out to the community regarding future options for that scheme.

Within the Makino Scheme, the floodgate at Reid Line spillway suffered some operational problems during the event mainly relating to the very high debris load. Horizons are currently implementing a range of measures to improve the operational reliability of this structure.

A REMINDER TO GET READY TO GET THRU 

An anniversary such as this is a good reminder to be prepared in the event of an emergency. To Get Ready to Get Thru it’s a good idea to have essential items on hand at home, in your car and at your workplace and have a chat to your family to create an emergency plan.

Check out www.getthru.govt.nz for further details on how to get prepared or contact the Emergency Management Officer at your city or district council to find out more about local hazards and response arrangements. You can also check out the Civil Defence Manawatu Wanganui Facebook page for the latest updates.

Above: Measuring river flow on the Makino Stream, June 21 2015

TOP TIPS FOR OUR NEW WEBSITE

Horizons has a new website and we encourage you to check it out. We are still at the same web address www.horizons.govt.nz but we hope you find this ‘new and improved’ version easier to navigate while sourcing the information that is important to you.

The Horizons team have put together our top tips to help you find your way around.

1.     Want to catch a bus? Click on the Bus Timetables link at the top of our home page to find bus timetables and detailed maps for Palmerston North, Feilding and Wanganui.

2.     What’s happening in your Region? Click on the Calendar link at the top of our home page to see all upcoming meetings and hearings. In the future the calendar will also include other events such as planting days, Field Days, community events and much more.

3.     What are our councilors talking about? Find out by looking at the Meetings Minutes and Agendas section which can be found either via About Our Region & Council or clicking on the Calendar.

4.     Have you seen our webcams? The webcams are one of our most popular online tools as they provide an interactive way to monitor water levels and weather conditions in the Region. There are now 27 webcams that can be viewed via our website and they can be found by clicking Webcams at the top of our homepage.

5.     Interested in environmental data for our Region? Our website has a wealth of information right at your fingertips. Click on Environmental Data and find information on river heights, rainfall, water quality and air quality and much more.

What's on - Council and Committee Meetings

June 2016

- Regional Council, 28 June, 10am

- Environment Committee, 29 June, 9am

August 2016

- Strategy and Policy Committee, 9 August, 11.30am

- Catchment Operations Committee, 10 August, 9am

- Passenger Transport Committee, 10 August, 9am

- Regional Council, 23 August, 10am

- Audit, Risk and Investment Committee, 24 August, 9.30am

6.     Want to find rates information for a property? The rates search box is under the Property and Rates tab on the home page. This tool is great if you’re looking to purchase a new property and want to budget what your rates would be – just type the address in and hit search.  

7.     Interested in reading our Long-term Plan? Important publications such as our Long-term Plan, Annual Plans and One Plan can be found by clicking on Publications and Consultation on our home page. 

8.     Keen to find out our latest news? Click on the News tab at the top of our home page to see our latest media releases.

9.     Want to receive our newsletters via email? Save the trees and sign up to receive Across the Region or one of our other newsletters via email. Newsletters can be found in the About our Region & Council section of the website.

10.  Still got questions? Click on the FAQS tab at the top of our home page to find the information you need. If you cannot find what you are looking for please call our friendly Customer Services Team on 0505 800 800 or email help@horizons.govt.nz and we can help you.

We hope you like our website and we appreciate your feedback, whether good or bad. Just call us on 0508 800 800 or email help@horizons.govt.nz to tell us what you think.

Other Events

- Horizons Road Safety staff at Mardi Gras, Ohakune, 25-26 June

- Refugee Driver Training Graduation, hosted by Red Cross, 27 June

- Ballance Farm Environment Awards Horizons Region Field Day, 30 June, 10.00am - 2.30pm, Email horizons@bfea.org.nz

- Entries open for Ballance Farm Environment Awards 2017, 1 August. Visit www.bfea.org.nz to find out more