Safeguarding our stopbanks

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Good weather days means good news for the project team and our contractors.

This issue provides more detail on the Stage 2 finishing works and the Stage 3 investigations, both of which are happening now.

We also have an important reminder about when to apply for a Bylaw Authority for those who have had the SOS work completed (Stage One and Two), and to let us know how you’d like to receive cut and carry notifications.

A quick recap on why this work is happening

Stopbanks are only as strong as their weakest link and are vulnerable to damage.

Over the years non-approved structures, trees and gardens have been established on public land. This can create weakness in the stopbank, which can cause water to flow through and lead to the stopbank failing.

This work involves removing some of the vegetation and structures to enable the repair and strengthening of the stopbank.

Stage Two: What’s happening?

To recap, Stage 2 is 95% complete with finishing work being done now in conjunction with Stage 3 works. There are two parts: Removal of the tree stumps next to the Rowing Club, and tidying and maintenance around the concrete floodwall along Henderson Street.

Earlier this month, the stumps were removed. This involved tracing their roots back to the size of a thumb, extracting them from the area, and then rebuilding the stopbank. This image shows the work in progress, where the stumps have been removed and the compacting work to repair the stopbank has begun. The work has been completed since these photos were taken.

The floodwall tidy up will be complete in the next few weeks.

Stage Three: Geotechnical work – Why are we doing this?

Unlike the previous stages, we have limited geotechnical data on file for us to access. This is why we are doing thorough testing in the area. This testing includes hand augers at every second property, and boreholes and Core Penetration Tests (CPT) around the start and end of the Stage 3 section.

A CPT is used to determine the properties of soils. This is done by pushing a steel cone (about 32mm wide) into the ground, and generally up to 20m below the surface (or until the cone reaches a hard layer). The steel cone contains an electronic measuring system that records tip resistance and sleeve friction. As the cone goes into the ground, measurements are constantly sent back to the rig and recorded on a computer. Once complete, the holes are refilled.

This data helps inform the design of our work programme for Stage 3.

After Labour Weekend, you can expect to see some activity on and around the Riverside Drive stopbank as the contractor starts on access and preparatory works for Stage 3 of the SOS project.

Fencing policy for SOS

At our September SOS Community Reference Group meeting, there was discussion around fencing as part of the SOS project and who is covering the costs.

Here’s a summary:

• We have a Rivers and Drainage Fencing Policy, which was updated in 2022. This policy covers all rivers and drainage schemes.
• We have used this policy as a guide, but adapted it to be fit-for-purpose for rear boundaries in the SOS project area.
• As such, for landowners in the SOS project area, Regional Council is covering the cost of a conventional wire mesh, timber railed or timber paling fence type (e.g. pictured), to a maximum of 1.8m high (we will also include a pedestrian access gate to the stopbank if requested).
• Where an owner chooses to construct a fence of a different material or style, we will ONLY contribute the cost of a conventional wire mesh or timber paling fence to a maximum of 1.8m high.
• We will NOT contribute to any additional feature components that the owner wants included as part of the fence construction – such as shaped posts, end caps or trellis work, painting, mowing strips etc.
• In practice, this means we use a quoted cost for the standard fencing as the basis for any contribution to alternative style fencing. Note, any private fence construction requires a Bylaw Authority (which the landowner will need to arrange).

Cut and carry: Contractor notifications

Previously, our cut and carry contractors have been putting notices in residents’ letterboxes to let them know when the work is due to happen. However, this hasn’t always worked well as the contractor’s schedule can change (largely due to wet weather).

To ensure communications are more timely and efficient, we will be moving to an email and text notification system for those neighbours who would like notification of pending cut and carry operations. The email and text notifications will replace the letter drop notices.

Residents who would like to receive the notification, please email riversanddrains@boprc.govt.nz, and give us your email address and cellphone number.

DIY’ing? Remember, you might need a Bylaw Authority

Thinking of getting stuck into a bit of DIY this summer? Before you dig, plant or build on your property, check if you need a Bylaw Authority for your activity.

What is a Bylaw Authority? A Bylaw Authority may be required if your property is near a Regional Council flood defence (such as stopbanks, floodwalls, drains and pump stations). It is written permission from us to carry out your planned works, with conditions in place to make sure that what you’re wanting to do doesn’t affect the condition of these flood defences.

It’s not to stop you doing work – just making sure that whatever work you do doesn’t accidentally affect the integrity of our flood protection and drainage infrastructure (which is critical to helping keep the community safe in floods).

Some activities that may need a Bylaw Authority include:

• Planting and/or removing trees and shrubs
• Building and/or removing fences and garden sheds
• Building and/or extending a house, shed or deck
• Constructing or removing retaining walls
• Landscaping earthworks
• Installing, upgrading or removing an in-ground swimming pool

If you live in the SOS project area (i.e. your property borders the base of the stopbank), you are in a Bylaw Applicable Area and, therefore, most works will need a Bylaw Authority.

Our team are here to help you through the process.

Find out more or contact our team on riversanddrains@boprc.govt.nz

2023-09-04 - September 2023 update

Welcome to spring and the official start of our construction season. This means the return of our regular SOS newsletter and, as we prepare to start Stage 3, we’re returning to our six-weekly distribution.

This issue outlines some of the work that’s due to begin and minor ‘finishing’ work that needs to be done to complete Stage 2. We’ve also included a reminder on bylaw property maps and the next Community Reference Group meeting.

If you’d like to have a chat about the project or have any questions about this update, you are welcome to contact us by email at riversanddrains@boprc.govt.nz or phone 0800 884 880.

Read the latest issue.

2023-06-15 - June 2023 update

Winter marks the traditional end of the construction season, so our teams are now making finishing touches to Stage 2, which primarily involves hydroseeding repaired areas of the stopbank and completing fencing work. The ongoing wet weather has made this work challenging so we’re keeping our fingers crossed for a decent run of sunshine to get things tidied up.

Over the next few months, the team will focus on gearing up for Stage 3. Physical works are planned to kick off in October. While the Stage 3 planning and preparation work is being done, we’ll reduce the frequency of these newsletters, with the next one planned for August. We’ll get back to our regular six-weekly distribution in September.

Keen to join your community reference group?

A community reference group, which includes residents impacted by the Safeguarding our Stopbanks work, was established late last year. The reference group provides a forum for sharing information, input on Council communications to residents, and feedback to the project team on what’s working well and opportunities for improvement. If you’d like to learn about the reference group or get involved, please contact Kirsty Brown, Rivers and Drainage Asset Manager via email riversanddrains@boprc.govt.nz

Please don’t dump rubbish and greenwaste on or near stopbanks

Illegally dumped greenwaste is expensive to remove and can cause damage to the gear our contracting teams use to maintain stopbanks – tree branches, flax leaves and mowers don’t mix.  Thanks!

Geotechnical inspections testing on public land

Over the next month or two you may notice some testing activity on the stopbank and berm area adjacent to the Riverside Drive stopbank. This work is part of preparation for Stage 3 of the project. The testing involves a hand auger that bores a small hole to sampling depths (the holes are filled once the sampling is complete). The analysis of the sampling information helps the team make decisions on what specific engineering work is required to remediate areas of the stopbank. You can expect to see a number of geotechnical specialists and engineers in the area from July onwards.

Sign up to your River Scheme

The schemes are areas of land where we maintain and upgrade flood defences, manage riverbank erosion risks and do drain maintenance. The Safeguarding our Stopbanks project is just one piece of work that we’re doing in the Whakatāne-Tauranga Rivers Scheme. To find out more on what’s happening across the scheme you can keep up to date via our website by subscribing to boprc.govt.nz/whakatane-tauranga-rivers-scheme Another way to see how this project relates to Council’s other work maintaining $442m worth of flood defences (floodgates, floodway and spillways) and the bylaws in place to protect them is to check out boprc.govt.nz/flood-defences

About your river scheme - Whakatāne-Tauranga

The Whakatāne-Tauranga Rivers Scheme covers the Tauranga River (previously known as the Waimana River), which has a 440km2 catchment and the Whakatāne River with a 1100km2 catchment. It stretches from Whakatāne town, Tāneatua and Waimana, south to Ruatāhuna and the Huiarau Ranges, and includes the Te Rahu, Waioho and Wairere tributaries. It is one of five major River and Drainage Schemes that were established in the 1970s by Regional Council (then known as the Catchment Commission) to effectively manage and maintain flood defences.

Why does the Matahina Dam ‘spill’ in heavy weather?

While relating to the Rangitāiki-Tarawera Rivers Scheme, our team is often asked “why does the Matahina Dam spill when it pours?” Here’s a quick rundown on the what, why, and how this happens.

In anticipation of, or during, heavy rain in the Rangitāiki River catchment, we will instruct Manawa Energy to ‘spill’ from Matahina Dam. This means they are required to release a controlled amount of water to lower the dam level in readiness of increasing river flows into the dam.

We do this to reduce the risk on communities below the dam by using the storage created in the dam to reduce peak river flows. This ensures downstream river levels are reduced from what they could be if this was not undertaken. In turn, this takes pressure off the flood defences and ensures everything is working together to help protect the community. During this time, water levels in the Rangitāiki River will remain higher than normal for a few days but will reduce slowly as the inflow into the dam reduces.

The river levels are closely monitored by our Duty Flood Manager during a heavy rain event until spilling is no longer required from the dam.

It’s a no go for trail and quad bikes on parks and reserves

Whakatāne District Council bylaws prohibit the riding of motorbikes and quad bikes on park and reserve areas. These vehicles can cause serious damage and are potentially dangerous to other users. If you see trail or quad bikes on or accessing the River Trail or riverside reserve, we encourage you to please contact Whakatāne District Council on 07 306 0500. Photographs are very helpful for enforcement purposes.

2023-04-11 - April 2023 update

Despite a wet start to the year, we’ve been making good progress on finalising Stage 2. We’ve included details in this update, what’s planned for Stage 3 and when this work is expected to be underway. We’ve provided an update on what’s happening with the inanga (whitebait) ponds near Stages 1 and 2.

Please don’t dump rubbish and greenwaste on or near stopbanks

Illegally dumped rubbish and greenwaste is expensive to remove and can cause damage to gear our contracting teams use to maintain stopbanks – tree branches and mowers don’t mix.

Stage 2 almost complete

This stage is divided into two parts, A and B. Stage 2 involves 20 properties, from 48 Henderson Street to 80 Landing Road and 2 – 6 Mananui Avenue. Due to consistently bad weather, Stage 2A progressed more slowly than expected, however it’s now complete, with repairs to the stopbank done and some finishing touches being made to grass cover and fencing.

Stage 2B involves work to the section of the stopbank where the floodwall is also located. Two teams have been working, with one removing vegetation and the other focusing on repairs to the stopbank. The teams are working with Whakatāne District Council to reduce the cumulative impact for residents beside the Hinemoa Stream, where a stormwater upgrade project is planned. We appreciate the ongoing support of residents and the positive feedback – thank you!

Stages 3 and 4 involve the stopbank behind Riverside Drive and this work is scheduled for the 2023/24 and 2024/25 constructions seasons (spring, summer and early autumn).

Why aren’t some trees allowed in certain areas on or near a stopbank?

Tree roots can grow through a stopbank and leave holes allowing water (seepage) to flow through it and cause the stopbank to fail. Tree roots can also get underneath floodwalls, lifting wall sections and breaking joints.

Stumps can also cause problems as they rot, leaving holes in the ground and potentially allowing water from sand layers beneath the ground to come up around the stump and impact the integrity of the stopbank.

Here are some photos from Stage 2 highlighting the risk of some trees and tree roots close to the stopbank and floodwall.

Members of the team checking out soil characteristics following removal of a large puriri tree.

Tree roots impacting the base of the floodwall and top of the stopbank.

Whakatāne Project Future Proof: What is it?

You may have heard that further upgrades to flood defences in the Whakatāne area are planned: Whakatāne Project Future Proof. This project will happen over multiple stages and involves upgrading the stopbanks and floodwalls along the town centre stretches of the river (from McAllister St Pump Station through to the Whakatāne Boat Ramp).

In April 2017, the Whakatāne district experienced widespread damage to homes, property, businesses, as a result of the events generated by ex-Tropical Cyclone Debbie. As the climate changes, communities across New Zealand are adapting to meet the challenges of a rising sea level and more frequent, more significant rain events that may cause flooding.

Using data gathered from historical events, as well as what we understand about the changing climate, we know town flood defences need to be upgraded. We have been working closely with the Whakatāne District Council and Te Rūnanga o Ngāti Awa and will be having conversations with the community in the future, to keep you informed about work that is planned.

Bylaw Authority records

The team has had some queries about prior Bylaw Authorities issued for work on a property that may not have been passed on as part of information when the property has been sold.

Any property owner in a Bylaw applicable area can contact the Regional Council to find out if a Bylaw Authority has been issued for the property previously. Council has records for all Authorities that have been issued since the original Flood Property and Drainage Bylaws came into effect in 2002.

It’s worth noting that the Safeguarding our Stopbanks work is being undertaken on public land to remove structures and plantings that present a risk to the stopbanks integrity. This work is being undertaken under a project specific issued Bylaw management plan.

The bylaws aren’t in place to stop people from doing any work on their land, but instead ensure any work carried out doesn’t inadvertently affect the integrity of Council’s flood protection assets.

Helping safeguard native fish species

Where and when it’s practical the Council team tries to include habitat restoration as part of river and drainage maintenance work. The inanga ponds at Ferry Road are a good example of this. Inanga are the most common native fish species caught as whitebait.

The other species that make up the whitebait catch are banded kokopu, giant kokopu, kōaro and shortjaw kokopu.

The work in the Henderson Street area requires fill material to strengthen and repair the stopbanks. Excavation of the inanga ponds along the river edge is a very cost-effective source of fill material which also avoids the need to ‘truck in’ fill through residential streets in close proximity to schools.

The ponds provide important refuge for native fish species that are otherwise vulnerable to predatory fish in the main river channel.

Ongoing planting of native plants around the ponds is being supported by Halo Whakatāne and Trees for Survival, who are working with local schools to assist students to grow native plant seedlings and learn about native fish life cycles and conservation values.