Geo-environmental review on impacts of Christchurch earthquakes...

Dr Amanda Black has reviewed the research on impacts on the environment from the 2010-11 earthquakes.

While our research focuses on the affects of the disaster on Maori communities, Amanda’s report serves as a reminder of the tremendous changes wrought on our landscape with 580,000 tonnes of silt and sand brought to the surface – the liquefaction we all noticed - and substantial damage to infrastructure (above and below ground), ruptured land surfaces and changes in hydrological patterns.

Our urban waterways were inundated with sediment and sewerage (20,000 m3 of sewage per day entering the Heathcote River), resulting in dramatic impacts on water quality and biological communities (i.e. fish, macroinvertebrates, and algae).

Amanda cites research by Lincoln PhD candidate Naomi Wells who found that the hydrological changes and mass sewage discharge had a catastrophic initial impact but 6 months after the February event, and following repairs to the wastewater system, there were no significant differences detected in water chemistry or nutrient (primarily nitrogen) cycling between those severely impacted reaches (Opawa and further east) and minimally impacted sites (west).

Within Christchurch city the Heathcote River/ Ōpawaho study area spanned an impact gradient from minimally affected headwaters in the west through severely affected reaches in the east (minimally, moderately, and severely affected from both sewage and liquefaction zones indicated with shading). The river drains into the Avon-Heathcote Estuary/ Ihutai to the east, where the Bromley Sewage Treatment Plant (STP) is also located.

While the recovery of benthic invertebrate populations has lagged behind that of organisms at lower trophic levels, this is a typical response in the recovery of streams and rivers and demonstrates their reliance on a specific range of water chemistry values and the presence of a food source.

This observation reinforces the importance of having relatively un-impacted areas (i.e., conservation areas) to re-seed ecosystems that are abruptly disturbed by natural disasters.

The report can be read in full through the following link:

A review of the environmental impacts from the Ōtautahi/Canterbury Earthquakes (Dr. Amanda Black)