Wai i te reporepo, wai i te wao: what nature tells us about how to understand and prepare for flooding
The Nature-based Solutions study will model nature-based methods to find out how they may lessen the effects of flooding and enhance biodiversity. The results will benefit the entire region.
This project aligns with our draft Strategic Climate Action Plan, the Hill Country Erosion programme and work being done by our Natural Hazards team.
The Otago Regional Council has been partnering with Kāti Huirapa Rūnaka ki Puketeraki to enhance the mauri and health of the Te Hakapupu / Pleasant River system in East Otago.
Together, we are on a journey to create a catchment restoration action plan to inspire us to sustain the awa. The plan aims to enhance the wider ecosystem, improve water quality by reducing the amount of sediment and nutrient input to the rivers and estuary, and use the best of Kāi Tahu mātauraka (knowledge) and modern science to sustain our efforts.
and restore biodiversity
As a regional council we are always looking for new and better ways to protect people, livelihoods and infrastructure. The Toitū Te Hakapupu Restoration project has built relationships and developed a knowledge base which make this catchment ideal for a pilot study modelling the use of nature-based solutions.
The year-long Nature-based Solutions Study, is fully funded by the Ministry for the Environment’s (MfE) Essential Freshwater Fund and will use work already done in the catchment to explore the potential of Nature-based Solutions or ‘green Infrastructure’ like wetlands and planting to help manage flooding, clean our water and support biodiversity in the region. We have engineering, water, planning and climate change experts helping us out and we’ll be combining local knowledge with international best practice to come up with ideas that could work.
Our partners have existing relationships in this area, so it makes sense to use this location as a pilot and get to work on a Feasibility Study which will be completed this year, to help us understand what might work and where.
An Engagement study, looking at perceived barriers and people’s willingness to adopt these ideas, will be finished in 2025. The results from both of these studies will help inform future decision making.
Known globally as Nature-based Solutions (NbS) these are practical ways to use nature's own processes to solve challenges and include things like wetlands to soak up floodwater and filter pollutants from stormwater run-off, and native planting to provide habitat for threatened species. These measures could be a win-win for the environment, industry and the local community, helping us play a part in reaching Aotearoa New Zealand’s environmental goals, while reducing the impacts of flooding and climate change on people and infrastructure.
Rather than engineering or built structures, natural solutions rely on green infrastructure - such as wetlands - to soak up floodwater and filter pollutants from stormwater runoff and native planting to prevent erosion, improve air quality and increase biodiversity.
- Once we have got a list of ideas, we will test these with mana whenua, industry and land user groups, like forestry, farming and lifestyle block owners in Te Hakapupu / Pleasant River before we finish the Feasibility Study.
- Once this report is complete, we’re planning to test some of the ideas more widely, with land users around Otago.
- At the end of the project, we’ll have two documents – a Feasibility Study focusing on possible designs for the Te Hakapupu catchment, as well as an Engagement Study about the opportunities and roadblocks to adopting nature-based solutions in the wider Otago catchments.
- From there we’ll be better placed to make a case around if and how Nature-based solutions could be rolled out in this region in future.
The feasibility study is investigating the opportunities, barriers, and practical viability of nature-based solutions within the Te Hakapupu | Pleasant River Catchment that could contribute to flood mitigation.
As climate change intensifies and flood risks rise, the search for sustainable solutions to protect people, infrastructure and biodiversity becomes more important. Nature-based solutions (NbS) are practical, cost-effective ways to use nature's own processes to solve challenges - think wetlands to soak up floodwater and filter pollutants from stormwater run-off, and native planting providing habitat for threatened species.
To evaluate how NbS may be applied to reduce flooding hazards within the Hakapupu catchment, a hydrology assessment and hydraulic flood modelling has been conducted. This modelling characterises how the current catchment will likely respond during an extreme rainfall event, in this case a one-in-100-year rainfall event (100-year annual return interval) with the added effect of climate change. The model simulates how rain, captured in the steeper inland areas of the upper catchment, flows through the main channels of Pleasant River, Trotters Creek, and Watkin Creek into the flatter areas of the lower catchment, causing flooding of farms, homes, and roads.
Based on historic rainfall data, the one-in-100-year rainfall event simulated in the flood model is projected to receive rainfall depths of 176mm to 190mm across the catchment. To put this in perspective, the flooding that occurred across North Otago in July 2022 was caused by between 110mm to 150mm of rainfall.
As part of our Nature-based Solutions study, we are carrying out a Feasibility Study investigating the practical viability of Nature-based Solutions within the Te Hakapupu | Pleasant River Catchment and whether they could contribute to flood mitigation.
A hydrology assessment and hydraulic flood modelling has been conducted, looking at how the current catchment will likely respond during an extreme rainfall event, in this case a one-in-100-year rainfall event with the added effect of climate change.
Next step: creating modelling looking at the same event, if Nature-based Solutions were in place.
The depth model above, in blue, illustrates the simulated depth of flood waters during an extreme rainfall event (one in 100 years), with flood depths ranging from 0 and 5m, to show where surface flooding is expected to occur.
The velocity model illustrates the flow speed of flood waters during a 1 in 100-year flood event, with flow speeds between 0 and5.6m/s, to show where flood water is pooling and where it is swiftly moving.
The ORC plays a crucial role in protecting and managing Otago's natural resources, including land, water, and air. We’re always on the look-out for new and better ways to work with others to make improvements.
Natural-based Solutions (NbS) are being used globally and in Aotearoa New Zealand to address environmental issues like flooding, climate change, biodiversity loss and water quality.
They are part of the central Government’s plan to address climate change and biodiversity issues and ORC’s new Land and Water Plan acknowledges NbS as a key method to achieve our objectives and overcome these challenges in our region.
This project is completely funded by the Ministry for the Environment’s Essential Freshwater Fund through the Government’s Jobs for Nature programme to create jobs while enhancing nature.
Nature-based Solutions (NbS) could be a game-changer, helping to address flooding and resilience, climate and biodiversity issues in one stroke.
Many of our lowest cost, highest impact natural hazard and climate change response solutions can be found within healthy, functioning natural systems.
Working with nature instead of against it brings a range of benefits – NbS can be cost effective, build greater resilience against flooding and climate change hazards, all while improving water quality and protecting biodiversity.
Practical actions like planting native trees and restoring wetlands can remove carbon from the air, build resilience to flooding and other climate impacts, and support a thriving natural world.
Globally, we’ve also seen the cost benefits to farmers and communities and opportunities in new areas, like restoration, sustainable farming and eco-tourism.
- Restoring wetlands and native forests: This helps to soak up carbon dioxide, filter water, and provide habitat for native species.
- Planting trees and vegetation: This can help to reduce soil erosion and flooding impacts, as well as improving air quality.
- Creating ecological corridors: This allows native species to move more freely across landscapes, which is important for their survival.
- Using natural materials for infrastructure: For example, using timber instead of concrete in construction can help to reduce carbon emissions.
- Promoting Economic Opportunities: NbS can create new economic opportunities through green jobs, eco-tourism, and sustainable agriculture.
Otago's diverse landscape faces various challenges, from flood risks and biodiversity loss to coastal erosion and climate change. Fortunately, NbS could offer promising options for tackling these issues simultaneously.
For this project we are focusing more on flood mitigation and water management and we’re looking into restoring and / or creating wetlands and planting.
Healthy wetlands are able to naturally absorb and store floodwaters, reducing peak flows and protecting communities from flooding.
Planting native trees and shrubs along riverbanks can slow down water flow and prevent erosion while providing habitat for native species.
The Feasibility Study will help us understand the benefits and impacts of different NbS in our region.
Scientists and ecologists are currently studying Te Hakapupu catchment and modelling how it could respond during flood events, both today and in the future, to understand the types of NbS we could look at.
We will be assessing the feasibility of potential NbS within the catchment to understand what solutions will be effective, practical to implement and sustain, and provide the greatest co-benefits for biodiversity, farming, and the wider community.
We will be talking to local iwi, and farmers and growers throughout the project to help shape the development of design options for NbS in this catchment.
The Feasibility Study for Te Hakapupu is expected to be complete in mid-2024, and engagement with the wider Otago catchments to come from mid – late 2024.
A project engagement report in the form of an Engagement Study will be complete by early 2025.
We’ve recently been working on another project in the Te Hakapupu catchment, which looks at improving water quality. As a result, we’ve already gathered a lot of knowledge about the area’s history and built strong relationships. This makes Te Hakapupu a great pilot catchment for investigating NbS options.
The catchment is prone to heavy rainfall events and floods that can cause significant damage to land, buildings, and infrastructure. Floods can also increase erosion and sedimentation, affecting water quality and aquatic habitats.
Climate change is projected to increase the frequency and severity of extreme weather events and floods in the future.
The catchment has experienced a significant loss of wetland area and quality over time, due to land clearance, drainage, and pastoral land use. Wetlands provide important ecosystem services, such as water retention, nutrient cycling, carbon sequestration, and biodiversity support. Wetlands also help mitigate flooding by absorbing and storing excess water and reducing peak flows.
We’re going to explore this as part of this work. We want to understand how much funding would be needed to make the rollout of NbS possible in Te Hakapupu and wider Otago, and whether local landowners or users would be interested in working with us - whether that be as part of the maintenance process or installation.
A number of ‘hard’ engineering solutions are currently used to manage flood risks in New Zealand, including things like stop banks, rock reinforcements on stream banks and gabion walls. In some cases, water channels are diverted, straightened, or deepened to increase capacity and reduce flood risk – and larger interventions could include dams and reservoirs. These hard solutions can often come with drawbacks, including high construction and maintenance costs as well as the potential for negative social and environmental impacts. Nature-based Solutions allow us to work more closely with nature, instead of against it.
It’s not a matter of completely replacing ‘hard’ engineering solutions but complimenting them. Hard solutions are found to be much more effective when used in combination with nature-based solutions, which can help to relieve the pressure on such infrastructure during large events.
NbS can help to protect your land and make it more resilient by reducing the impacts of flooding and erosion, improving soil health and water quality. This is an opportunity to work with Council and gain support to implement solutions that are co-beneficial for your land and the wider environment.
Depending on the kinds of NbS being considered – some landowners and users have created recreation and tourism opportunities, as well as economic benefits around planting trees or crops that can be harvested.
In a broader sense - it’s also an opportunity for New Zealand farmers and growers to continue being world-leaders in sustainable land and water care practices.
This project is a pilot in Te Hakapupu to test the feasibility of working with local land users to implement nature-based solutions on their land. As part of this, we’re hoping to work with lots of different members of the community – not just those who own land, but also those who have an interest in planting or caring for natural areas. We want to understand if they would like to work with us in future to help make nature-based solutions thrive here. And that could be anyone from local schools and community groups to highly interested individuals.
The Toitū Te Hakapupu Restoration Project is a separate project that was funded by the Ministry for the Environment back in 2021. The aim of the Restoration Project was to work with local Mana Whenua, community and stakeholders to improve water quality in the catchment.
While the Nature-based Solutions Project has a flood-prevention focus, one of the potential benefits of their installation is improved water quality – meaning there is a lot of cross-over between the groups and individuals interested in both projects. As a result of this cross-over, the Nature-based Solutions Project will draw on the technical findings, engagement learnings, and relationships that were built in this catchment during the Restoration Project and use them as a starting point for their investigations.
To learn more about the project email the project manager Melanie White.
Or follow the links below for more information about:
What the Ministry for the Environment is doing, and case studies of nature-based solutions from around the country, visit: Working With Nature
Previous ORC projects in Te Hakapupu, like the Toitū Te Hakapupu Restoration Project
Hinoka kai tō rohe Projects in your area
Otago, New Zealand's third-largest region, features diverse landscapes like rugged coastlines and majestic mountains. We prioritize sustainability and collaborate with mana whenua and the community on projects. Explore our ongoing initiatives.
Toitū Te Hakapupu: The Pleasant River Catchment Restoration Project
A partnership project with Kāti Huirapa Rūnaka ki Puketeraki to improve the health of the rivers and estuary in the Pleasant River Catchment.
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