"It's mitigation because the Otamaraho realignment on State Highway 2 saw the stream moved, affecting the ecology and the spawning grounds for eels," Morry Black of Ngāti Kahungunu, said.
"We've had to come together to help fix it up. This is about bringing back the eco-system because the realignment of the state highway made quite a bit of mess. This is also about rebuilding our relationship with NZTA. "
NZTA and Horizons paid to fence off the land, with Horizons supplying the flax and 2000 native plants.
James Kendrick, of Ngāti Kahungunu, said he was thrilled to see so many people turn up to help.
"This is about starting to build the gap between Māori and non-Māori and we're doing something for the next generation."
Logan Brown, the freshwater manager for Horizons, said the project was part of the Tū Te Manawa project.
"We planted 2000 natives today, with 500 flax six months ago. We'll let these plants grow and in three or four years we'll return and plant podocarps such as tōtara," he said.
"When you have riparian shading bugs fall into the water for fish to eat. Stock exclusion also helps."
New Zealand First MP Ron Mark also arrived to help with the planting.
"I love these projects," he said.
"When NZTA began it's realignment they didn't consult with iwi or hapū and a lot of habitat was lost. It was an absolute tragedy. That a government agency was part of the destruction of a habitat . . . It's good to see NZTA accept they need to be part of this. We can't change what they did, but this is about going forward."