Canterbury Floods: Drone Footage Reveals Ecosystem Damage & Long-Term Risks

Canterbury Floods Leave Ecosystems Damaged, Eel Fisheries Vulnerable

Drone footage is revealing the extensive damage caused by recent floods across Canterbury, New Zealand, with experts warning of long-term impacts on the region’s ecosystems. The footage, captured by 1News, shows widespread inundation approximately 45 kilometers south of Christchurch, transforming the typically clear blue waters into a muddy brown.

Maitu Prebble, of the local Wairewa Rūnanga, stated that “potentially hundreds, if not a thousand or more” tonnes of sediment have washed into Wairewa/Lake Forsyth. The murky water is now spilling into the coastline, leaving a visible stain along the water’s edge.

According to Prebble, the discoloration is due to clays originating from the surrounding landscape. The sediment has been carried down from various rivers, hill country, and cliffsides. A significant contributor is loess, a type of wind-blown silt capping the Banks Peninsula, which is particularly vulnerable to erosion during heavy rainfall.

The influx of sediment is already impacting aquatic plants that were previously introduced to improve the lake’s water quality. “There will be no light penetrating the water’s surface, so being photosynthetic plants, they’ll be suffering under these conditions and probably dying back,” Prebble explained.

The floods also pose a threat to Wairewa’s significant eel population – the highest density of eels in any New Zealand catchment. Many eels likely migrated out to sea when the lake was opened following the flooding, leaving the eel fishery “pretty vulnerable for this season,” Prebble said.

Environment Canterbury (ECan) is currently collecting samples to assess the nutrients washed down from the surrounding soil. Elaine Moriarty, ECan’s water and land science manager, indicated that there will be “no quick fix” for the lake. She explained that wind will continue to suspend nutrients, leading to a gradual release of nitrogen and phosphorus, potentially causing long-term problems like toxic algae blooms.

Toxic algae can be dangerous to both animals and humans in the area, and conditions will be closely monitored by the rūnanga and ECan in the coming months.

Despite the challenges, Prebble expressed confidence in the community’s ability to adapt. “It’s embedded and inherent in the name of the lake, which is called Wairewa, which means water’s rising rapidly,” she said. “We know from the past that this ecosystem here changes massively, but what we do also know is that our people for our time have adapted to those changes.”

The wider Canterbury region has been significantly impacted by the recent destructive weather system, prompting a state of emergency. Aerial footage has revealed the scale of the flooding and the isolation of communities across the area.