Source: Environment Canterbury Regional Council
Riverbed management
Rivers have many functions. They carry millions of tonnes of sediment, are home to natural habitat, are teeming with biodiversity and provide mahinga kai and recreational values for those who connect with them.
Historical imagery shows a reduction in open gravel area and general increase in weeds on previously active riverbeds across the region meaning they require active intervention to manage food risk. Weeds tend to slow flood flows, raise water levels, encourage deposition of sediment, and potentially force floodwaters around obstructions.
Flooding does a good job of flushing sediment out of river systems but as the flow is reduced, particularly in larger braided river systems, the sustained flow that historically carried sediment and gravel out to sea even when not in flood, has reduced.
In some rivers across the region there is a gravel aggradation issue and in some places the bed is building up. We encourage gravel extraction in those areas as much as we can.
Gravel extraction generally compliments other flood protection measures such as maintaining vegetated buffers, construction of flood protection works (such as stopbanks and rock erosion control), land use planning and emergency preparedness. Flood protection schemes are designed and maintained to certain levels of flood flow and there will be flood events that exceed those capacities. In these instances, we expect that out of river flooding may occur.
Community input
Ensuring those who live alongside rivers have a say in developing solutions for flood protection is critical to the work we do. We must also balance the ability of the community to pay and ensure continued protection while any change is investigated and implemented.
We are currently reviewing the regional planning framework for Canterbury. This process seeks to align our planning framework with national direction such as the National Policy Statement for Freshwater Management 2020 (NPS-FM), including Te Mana o te Wai.
This includes the current ‘Our Future, Canterbury’ campaign, which is gathering community views on what we should prioritise. It will inform the 2024 Long-Term Plan and then the drafting of our Regional Policy Statement.
Header image: Rakitata/Rangitata River.
