Our environment is hurting too

When Hawke’s Bay Regional Council (HBRC) scientists tested the quality of water in the Eskdale River in early April, they found one lonesome bug. 

“This means the river is pretty well lifeless,” says Science Manager, Dr Anna Madarasz-Smith.

When Cyclone Gabrielle slammed into Hawke’s Bay unleashing rainfall levels 500% above normal, and river flow averaging more than 1000% above normal, it set in motion a chain reaction of events that are still unfolding in our landscapes and natural environments.

Here’s another example. Waitangi Park and the adjacent Waikahu wetland on our Hawke Bay seafront were ravaged by the cyclone. Even in early April, the area looked like a bomb site with flax and grasses contorted backwards, dried silt and mud jostling for room with piles of wood debris, and bits of jack-knifed railway track lying about.

In 2018 Ngāti Parau hapū and iwi, Forest and Bird and other organisations worked alongside HBRC to create the 15-hectare Waikahu wetland focused on restoring the mauri of the awa by providing new habitat for mahinga kai and taonga species.

Although it’s thought the wetland is recoverable, the cyclone has nonetheless wiped out years of patient restoration work, and it’s not just the plants that are suffering.

Ngaio Tiuka, director of the Ngāti Kahungunu Taiao Unit, wonders about the special spawning grounds created for fishes, and inanga (whitebait) in particular, to migrate into the wetland.

With the wetland lying two metres above the Tūtaekurī River, a fish pass mimicking a small stream was built with resting pools for the fish to pause on their journey.

Inanga normally spawn on a king tide laying their eggs in grassed areas where water transitions from salty to fresh. A month or so later, and on the next king tide, the eggs hatch and the juveniles all go out into the river and then out to sea. 

“But the storm has modified their habitat,” says Tiuka. “The river banks have been scoured out and are now too steep for fish to get up. Inanga spawning is likely to suffer.” 

If these things are happening at one wetland and one river, what is the ecology like across HB’s many streams and estuaries? Are there plenty of macroinvertebrates like crabs, bivalves, worms, amphipods to keep the water healthy? 

HBRC’s Pieri Munro says understanding the impact of the cyclone event on our rivers, lakes, estuaries and coast, as well as on our land, will take many months of data collection and analysis. 

“It is also likely that these effects will last for many more months,” he says, “as sediment deposition in rivers and estuaries continues to impact ecosystems.” 

HBRC’s science team is working with top scientists from NIWA, GNS and New Zealand universities to measure and understand the impact of cyclone Gabrielle on our environment. Slips, landslides and areas of soil erosion are being mapped, measured and tested for their stability, and laser technology is being used to understand how river channels might have changed with the floods and therefore potentially behave differently in the future. 

Professor James Brasington, director of the Waterways Centre for Freshwater Management at Canterbury University and working with NIWA and HBRC, has developed 3D models of flood affected regions of Hawke’s Bay and Gisborne using high resolution helicopter laser scanning. With this data he had been able to map, by early April, the distribution of silt (sediments) deposited in the Eskdale Valley and said then “we estimate the flood deposits from Cyclone Gabrielle [in the Esk] are about 8,500,000 tonnes”. 

The recently-formed Silt Recovery Taskforce comprising HBRC and Hastings District Council (HDC) staff says it will likely take many months, if not years, to remove silt deposited on orchards, farms, roads and residential properties across the Hastings district – depending on how much is recoverable. 

But let’s pause here. Is it sediment? Or silt? Or both?

Associate Professor Peter Almond, from Lincoln University’s soil and physical sciences department, says ‘silt’ is being used as a generic term for the sediment that has ended up on floodplains in Hawke’s Bay and Tairāwhiti. 

And local soil scientist, Phillip Scofield says the sediment that came down our rivers is made up of various proportions of silt, sand and clay depending on the rate of water flow that distributed them. Each has a different mixture of soil particles:

• Clay – less than two microns in size. Soft and sticky, and shiny and smooth on the surface.

• Silt – the particles between two microns and 50 microns. Soft and smooth. Silky between the fingers. Has ripples and patterns to it.

• Sand – bigger particles again from 50 microns to 2 mm – then it’s called gravel.

“Silt, sand, and clay is about half of what a really healthy soil is,” says Scofield who is Chair of the HB Future Farming Trust. “The rest is mainly air, water, and organic matter.”

He is hopeful that sediment that is only about half a metre deep can be remediated by getting life living in it again as soon as possible, “getting roots in it, aerating it and rebuilding it”.

We know sediment has damaged some 4,000 hectares of arable HB land and 47% of crops, and wreaked havoc on people’s lives and homes.

But what about the sediment that has been spewed out to sea by the Tutaekuri, Ngaruroro and Eskdale river mouths, and there, mixed with among other things, sewerage that has bypassed the biological trickling filter plant at Napier City Council’s damaged sewerage treatment station?

Pieri Munro says because of contaminants from urban and rural land flushed into our waterways, rivers and beaches across Hawke’s Bay remain unsafe for swimming. He says HBRC water quality monitoring is ongoing and BayBuzz understands results will feed into both LAWA (Land, Air, Water Aotearoa) National River Water Quality updates and HBRC’s next SoE (State of the Environment) reporting.

It is also likely, that because of land and stream bank damage, any rain event could remobilise sediment output into our sea.

And in fact, many of our inland streams and waterways have been gouged out with flooding, riparian plants that have died or washed away, and trees fallen or dying a slow death because their roots have been immersed in water for too long.

The once picturesque Karamu Stream walk weaving below Havelock North is an example of this – a ghost of its former self.

Planting at Irongate Stream, which flows into the Karamu at Longlands, “has been pretty well wiped out,” says Tom Cole, tree planting co-coordinator for Forest and Bird’s Havelock Hastings branch.

“The flooding caused the water to pond and some 4,000 trees and over 30 species planted by Forest and Bird in the last two years are gone.”

“It’s disappointing but I guess if you plant on a flood plain this is the risk. We will need to discuss whether to re-plant or change tack for the future?”

Cyclone damage to Te Mata Peak was “significant”, says Mike Devonshire, chair of Te Mata Park Trust.

“We estimate over 100 slips occurred throughout the Park and we lost several hundred young trees due to the slips. Many larger trees were lost, and more were damaged that have since been removed due to safety concerns.”

With trees down across the Bay and bird habitats lost, many say they’ve noticed a reduction in bird numbers and an increase in insects.

“Flooding displaces many pest animal populations from their natural habitat,” explains Pieri Munro. “Add to this widespread debris and spoilt agricultural produce and potentially it fuels an increase in populations.”

Farmer and Gimblett Gravels viticulturalist Bruce Wills says there are “definitely less birds about”, though he doesn’t have hard evidence other than not needing bird nets on his grapes this year!

Wills is Chair of the QEII National Trust and a past National President of Federated Farmers. He has been up in a helicopter surveying cyclone damage on our inland farming landscapes and gives me a birdseye view.

“Some areas have been untouched while others have been wiped off the face of the earth,” he says. “Trees are down everywhere and 100s and 100s of kilometres of fences have been severely damaged or lost, particularly in gorges and steep areas

“Our national practice of riparian planting has been destroyed too with scores of kilometres washed away. In some cases flaxes have been unearthed and have floated down narrow flooded streams blocking them.

“Riparian planting is nice to have and good for keeping stock away from the water. But now there is a whole question around riparian planting. It’s not the golden panacea we thought it was. I talked to one farmer that had seven kilometres of riparian planting on a small but significant stream. He’d spent time and money on this but not a single plant is left now and no fences. What does he do now? We are encouraged by government and council to do this stuff. But is it sensible to go back and repeat?

Also a member and former president of the NZ Poplar and Willow Research Trust and member of the Right Trees, Right Place Trust, Wills says it is estimated that pinus radiata accounts for 80% of Gisborne’s foreshore debris, while wooded debris that’s washed up on Hawke Bay’s foreshore is only about 20% pinus radiata. [A HBRC report that came out after this assessment confirmed that HB foreshore debris consisted of a mixture of pine, willow, poplar and ‘other’. At all but one of the surveyed sites, there was little evidence of slash, indicating that the majority of pine came from erosion of hillsides and streambanks.]

Another new dilemma for Bruce Wills and QEII is what to do with covenanted native plantings that have been destroyed in the cyclone. There are more than 250 covenants on farm lands across Hawke’s Bay. Once land is covenanted it is legally retired for conservation “in perpetuity”.

“How are we going to manage this,?” asks Wills. “If a block of bush has been destroyed should we covenant it? Or do we consider uplifting the covenant? We’re going to have to be pragmatic and make sensible calls. It’s too early to assess exact numbers and damage but it is something we have to consider.” 

Ask Wills to tell us in one sentence what we need to do to protect farmland from future cyclones and he says, “plant trees, keep stones out of the rivers, and shoot deer.”

Conservationist, scientist and chair of Biodiversity Hawke’s Bay’s Trust, Charles Daugherty says deer are contributing to HB and NZ’s carbon emissions. “They undermine biodiversity initiatives big time by causing soil and vegetation loss that makes flooding worse when it happens.”

To find out more about this, I contemplate the Kaweka and Ruahine Ranges as I sit talking with retired Taradale land management specialist Garth Eyles.

Eyles began his career with the Ministry of Works and has worked in land and soil management and biodiversity programmes all his working life.

“The importance of the Tararua, Ruahine, Kaweka, and Kaimanawa ranges to Hawke’s Bay is not understood by most people,” says Eyles.

“These ranges are where our rivers start and where our water supplies come from. However, the ranges are unstable. They comprise very broken and easily shattered greywacke rock.”

Eyles says HB’s land is young – just a baby – at two and a half million years old with the greywacke at its surface constantly shifting. (By comparison Australia is billions of years old.)

“We think we can stabilise our land, but we can’t. Geologically it’s an active environment.”

The Ruahine and Kaweka with their unstable greywacke are where the highest rainfalls occur both in volume and intensity. And it’s this combination of natural instability and location that make the ranges extremely susceptible to massive erosion during major rainfall events.

“The only natural condition limiting this risk is the quality of the native vegetation that holds the surface together,” says Eyles. 

And here we return to the subject of deer. He has long worried about the fragility of the greywacke and how feral deer in ever increasing numbers chomp down the native forest’s understory exposing rock so that when a cyclone hits “all hell breaks loose” as about 40% mudstone and 60% sandstone greywacke is swept in bulk down into the rivers to become sediment and gravel. 

In January 2022 Eyles wrote a Talking Point in Hawke’s Bay Today arguing that a lack of effective deer control for the past 40 years had severely damaged the vegetation on the HB mountain ranges. 

“At a time of climate change when rainfall intensities are meant to increase, it is ludicrous that the administrations of DoC and HBRC have allowed the potential erosion risk in the ranges to increase,” he wrote. 

“All that is needed is a cyclone hitting the ranges and waves of gravel will once again come down the rivers …”

Eyles was on the metal. The rest is history. 

Now more than ever, he wants to see feral deer wiped out of our ranges. 

“In recent years we have had so much sediment channelled out to sea by our stopbanks,” he says. 

“Now we need bigger stop banks because we don’t look after our mountain land properly.” 

Hawke’s Bay’s taiao, from our mountains to the sea, is hurting. And yet it is this same environment, and the way we treat it, that for many can be part of the road to healing, resilience and to a new future.

Kia whakatōmuri te haere whakamua – “I walk backwards into the future with my eyes fixed on my past” – is relevant here. New thinking in landscape architecture showcased in a viewpoint in Newsroom after the Auckland floods [https://www.newsroom.co.nz/comment/practical-strategies-for-climate-change] suggests if we pay close attention to the underlying indigenous landscapes beneath our urban areas, we may better be able to ‘slow down’ the impacts of flooding.

Garth Eyles notes core sampling from Lake Tutira that shows there have been seven storms bigger than Cyclone Bola in the seven thousand years since it was formed. 

Flooding is deeply embedded in our region’s history. There is a story of missionary William Colenso in his whare at Waitangi Mission Station in Clive, in the mid 1840s, getting out of bed one evening only to find himself wading in water. On opening his front door, he saw a waka and its occupants paddling passed. 

Colenso called the Heretaunga Plain “a dirty great swamp”.

The first big flood recorded in Hawke’s Bay was in June 1867. The next, in 1897, with newspaper stories uncannily similar to ours for Cyclone Gabrielle. 

“Never in the history of Hawkes Bay has there been such a disaster,” The Auckland Star reported on 13 May 1897. “…terrible floods caused great loss of property as well as loss of several lives … just after dark the large embankment at Redcliffe, near the Waiohiki native reserve, at the back of Taradale, burst, being carried away by the great pressure of the flooded Tutaekuri River. Almost at the same time the Ngaruroro River, which flows into the sea at Clive, broke through the railway embankment at Waitangi …” 

A 1938 flood reported 12 feet of silt in some places in Esk valley. In 1980, the Ngaruroro, despite the diversion scheme, broke its banks and 20 kilometres of stopbanks were replaced. There was flooding with Cyclone Bola in 1988 and then in 2018 major flooding and silt again in Esk Valley.

“Why not slowly allow our rivers to return to their original channels and flood plains, as recent floods show they always will?” asks Biodiversity HB’s Charles Daugherty.

“We’ve taken away the rivers’ capacity to deal with, and usually contain, heavy rainfall on the land through wetlands and wide river plains, and their capacity to restore aquifers.”

He suggests we need to start planning for managed retreat. “Countries around the world are implementing this, and guidelines are developing. We’re a huge province and we’ve got room to move people away from the coasts and floodplains.

“The odds are we will get more and bigger storms with the warming of the oceans and atmosphere bringing more rain. And with that don’t we all have a responsibility to think differently as we try to fix things in the aftermath of Cyclone Gabrielle?”

One person whose full time job is to think about our rivers and waterways, is Nathan Burkepile. He cut his teeth on a big natural flood plain management scheme with First Nations in the United States. He is a trained ecologist and now NZ Landcare Trust’s Hawke’s Bay regional coordinator supporting catchment and community groups with the aim of improving our water quality and our environment.

Nathan’s call to action is that “we have to hold water on our land”.

“For a hundred-plus years we’ve drained the land to get water off as quickly as possible. If we hydrate the landscape, water would filter naturally through our land, sink into the ground, reduce downstream flooding and reduce the impacts of drought.

“We need to restore our wetlands, streams and rivers, and plant more trees (mainly natives) in our paddocks to hold water on our land.”

Ironically, Burkepile says Hawke’s Bay could be facing a drought next summer and this concept of “holding water on the land” is the same way to mitigate for heat as for floods. “Water held on the land cools it by as much as two degrees.” 

He says we treat our streams like the Karamū and the Taipo as drains pushing water through them instead of letting them connect to the flood-plain and flood regularly. He cites Karituwhenua Stream in Havelock North where he has worked with the Fulford Road Landcare Group placing leaky log weirs into the stream to “slow the water down”.

During Cyclone Gabrielle the Tukaekuri and Ngaruroro breached their stopbanks in 22 places – a total of 5.4 kilometres of broken stopbank, 28 kilometres of weakened stopbank, while 190 kilometres is still intact. The broken bits have largely been fixed now by HBRC and Burkepile is not advocating we get rid of them.

“We have to work with the stopbanks,” he says. “But we need to start buying land back either side of them and start pushing them out so the rivers have more room to breathe and we build bigger bridges over them.” 

I drive with Burkepile out to Maraekakaho where we look across a lumpy paddock – an old flood plain – to the Ngaruroro stopbank. He suggests we start widening our rivers in their upper catchments – like the place he and I are looking at. “See,” he points, “you could lose marginal grazing land here and gain flood protection to stop flooding further downstream.” It would also encourage water to seep down into the groundwater, or water table, and re-charge the Heretaunga aquifer.

“If we lose some productive land in this process of making room for the rivers perhaps we could grow crops on the floodplain,” suggests Burkepile. “And perhaps we could use raupo to create a new fibre.”

Burkepile says we’re stuck with a legacy of alluvial geomorphology in Hawke’s Bay, but “we need to start moving towards natural flood management. We need to do a cost-benefit analysis and reassess.

“It’s time to press the reset button.”

Ngaio Tiuka oversees the aspirations of Ngāti Kahungunu for the use and management of marine and freshwater fisheries within its rohe and is responsible for providing high quality analytical advice and research.

He says in terms of how rivers are managed, including flows and flooding, their ‘mana’ and ‘mauri’, his iwi had already been supporting the concept of ‘making room for rivers’ before the cyclone.

He sees giving true respect to ki uta ki tai (mountains to sea) and the natural processes of our waterways – including protecting and reconstituting natural flood plains, limiting river encroachment, widening stop banks, re-zoning areas unsuitable for housing and certain land uses, indigenous revegetation and creating or enabling more wetlands and estuaries – “are all part of building back better and working with the taiao”. 

“Some people think we want to go back to the dark ages.” He laughs. “We don’t. This is about sustainability, being pragmatic and logical. This is more than a ‘nice to have’ environmental aspiration. Who doesn’t want to look after their drinking water, enjoy our waterways or dare I say, be safe from flooding.”

Te Ao Māori view of the environment is that “it’s not something over there separate from us,” says Tiuka. “We are part of the taiao and we have to look after natural processes and work within limitations. How much we take from our waterways for example, what do we put in them? 

“We can’t just exhaust nature’s resources.”

The Environment Centre Hawke’s Bay agrees. It has put together an advocacy paper asking “how can we create climate resilient communities in Hawke’s Bay after Cyclone Gabrielle?”

“Our immediate reflex will be to rebuild what has been lost, and in the same way,” says spokesperson and CEO, Emma Hogan-Heke

“But the way we have built and planned in the past has made our communities vulnerable to the impacts of climate change. Now is the time to step back and rethink things holistically and intergenerationally, and to restore our communities in a way that is more resilient and supports healthy people and ecosystems.”