Tree planting can reduce flood risk, say wildlife and watershed groups

Spring melt is receding on the St. John River and so far there has been no major flooding.

The public safety department reports that the river is well below the flood stage and the five-day forecast calls for a further drop in water levels.

River restoration experts say there is a way to increase the likelihood that future floods will also go smoothly.

Simon Mitchell of the World Wildlife Fund and Natalie Deseta of the Nashwaak Watershed Association say planting trees, shrubs and grasses along the river and its tributaries can help reduce the risk of severe spring flooding and extreme rainfall.

“When we think of floods,” said Mitchell, “our biggest problem is the frequency and intensity of these events.”

Mitchell is a habitat specialist studying the St. John River and vice president of WWF Canada based in the Nackawic area.

“We have to do everything we can to keep the water in the landscape,” he said, “whether it is trees or wetlands that act like a sponge and then slowly release this water.”

Mitchell commends groups like the Kennebecasis Watershed Restoration Committee and the Nashwaak Watershed Association for their work.

Nashwaak Watershed Association staff and volunteers are planting at Neil’s Flats restoration site. (Submitted by Natalie Deseta)

Volunteers and staff have planted thousands of maple trees in the lower 70 kilometers of the Nashwaak River in recent years, along with native grasses and shrubs such as willow and alder.

“The silver maple is a really great candidate for mitigating the effects of flooding,” said Deseta.

She is the restoration and public relations coordinator for the Nashwaak Watershed Association and has an academic background in geology and environmental sciences.

“On a hot summer’s day, a fully grown silver maple can absorb up to 220 liters of water per hour,” said Deseta.

“You really love water.”

“Your entire life cycle is actually about the flooding process.”

Natalie Deseta says homeowners will often find their property quickly deteriorates when trees are removed from the riverside. (Submitted)

Trees are planted in the highlands within the river terrace, Deseta said.

Willows and alders are planted right on the bank where they come into contact with the river.

They are “really great for dealing with the flow of water,” she said.

“They are flexible and can swim with the flow and divert the force of the flood.”

Varieties of native willow shrubs include red tips and sandbars.

Native grasses have very deep roots, she says, and can hold the riverbank together and prevent it from being washed away.

By the beginning of this year, Deseta said, 14,093 trees, 25,998 shrubs and 4,958 acorns had been planted along the 46.6 km long coastline.

An intact silver maple floodplain forest in autumn (Submitted by Natalie Deseta)

The Nashwaak is one of many rivers in the province whose banks have been cleared from trees for agriculture or homeowners who wanted a view.

In the northern parts of the river, bure oak and red oak would be more common in the riparian corridor than silver maple, Mitchell said.

“We have 32 native trees here in New Brunswick and they can help us in the right place at the right time to change the curve of climate change and biodiversity loss.”

Mitchell said WWF is working with other conservation groups and communities on a number of restoration projects.

“We need to do this in many more places across the Wolastoq watershed,” he said.

“We could look at any tributary,” he said, naming the Meduxnekeag, the Kennebecasis, the Tobique, the Oromocto, and the Hammond.

The executive director of the Nashwaak Watershed Association, Marieka Chaplin, and some indigenous redtip willows grown in a greenhouse. (Submitted by Natalie Deseta)

Restoring is not as easy as planting, Deseta said.

Flood plantations require constant maintenance, she said.

The hay has to be mowed year after year so that it does not displace the seedlings.

She hopes that private homeowners will still pay off to take on good stewardship and avoid property damage.

Although there are regulations against felling trees within 30 meters of a river without provincial approval, Deseta said homeowners should reconsider the idea.

Property owners could see damage almost immediately after trees are felled and replaced with something like lawn, she said.

“The soil is no longer able to suck up precipitation or floods. You will be building up quite a lot on your property for the first five years. And over time the river will adjust and potentially wash away the riverbank quite a high rating. “

“In some areas in the watershed, we are talking about a bad year with floods of up to half a foot per year.”

At least five meters of trees and vegetation are required along a river, Deseta said, to mitigate the effects of water quality degradation, erosion and flooding due to forest clearing.

Planting along rivers doesn’t just help people, Mitchell said. It’s also good for everything that lives in and around the water, from river otters to birds to fish.

The vegetation on river banks prevents sediments from entering the water and harming aquatic life, he said, and it also creates shade to keep cold-water species like salmon cool and alive when water temperatures rise.

“We cannot act fast enough,” said Mitchel, “to tackle the combined crisis of climate change and biodiversity loss.”