Restoration and management

A wide range of actions can help to enhance the health of large rivers, including reducing point source contaminant inputs, maintaining ecologically-suitable flow regimes, and reducing catchment sediment and nutrient sources. Recent overseas work on large river restoration has focussed on reconnecting hydrological linkages with habitats that have been disconnected as part of flood protection works or to facilitate navigation. These habitats include floodplains, backwaters and side-arms, sometimes referred to as hydraulic retention zones, where reduced water retention times alter ecological processes such as sedimentation, plant growth and nutrient retention. Revegetation and reconnection of areas of floodplain may increase natural function but may provide additional spawning habitat for invasive species so needs to be managed carefully.

Current projects

We have recently worked with Fish & Game to understand factors affecting macroinvertebrates, fish and waterfowl communities in constructed ponds on the lower Waikato River floodplain. This work is currently being written up. In addition, LERNZ researchers are investigating the role of vegetation cover and connectivity as factors affecting the resilience of zooplankton resting stages in floodplain soils. We are also working with colleagues at the University of ConcepciĆ³n to determine whether Chilean rivers can provide a reference template for New Zealand large river restoration.

Contact: Kevin Collier

Completed projects

LERNZ researchers have investigated the effectiveness of side-arm reconnection to create hydraulic retention zones for processing nutrients and trapping sediment, as well as for generating phytoplankton and zooplankton for downstream food-webs. We have also conducted high intensity physical and chemical characterisation of the lower river to identify zones of similar character to guide management. Working with Waikato Regional Council we have conducted hydrodynamic modelling of floodplain lake and delta ecosystems to provide an improved basis for management.

  • Pingram, M.A.; Collier, K.J.; Hamilton, D.P.; David, B.O. In press. High intensity data survey and multivariate statistics reveal ecological zones along the longitudinal profile of a large, temperate, lowland river. River Systems.

  • Ginders, M.A. 2011. The influence of connectivity on the functional role of a natural and re-constructed side-arm in the lower Waikato River. Unpubl. MSc thesis, The University of Waikato, 135 p.