Part B: River engineering for flood control: instream ecological effects and how to monitor and manage them

Communities and regional authorities around New Zealand actively manage river corridors to protect lives and property from flooding and erosion. There are a variety of methods to control and manage the impacts of flooding, with key actions including stop-banks, gravel extraction and managing vegetation within the active channel. In addition, various forms of bank protection are routinely employed to prevent erosion, such as rock walls, groins or managed willows. While these techniques can be effective at reducing flooding and erosion risk, they can have negative impacts on river health. Impacts include altered hydrology, reduced habitat complexity and reduced connectivity with floodplain habitats (e.g., riparian areas and floodplain wetlands). Collectively, these effects can reduce fish and macroinvertebrate habitat quality with flow-on consequences for overall river health.

This webinar will discuss the potential ecological impacts of river engineering (for flood control) and pair these impacts with potential actions to minimise and / or mitigate instream ecological impacts. This session will draw on the general river management literature and reflect on my recent experience in the Hawkes Bay region. Here I was involved in developing an ecological monitoring plan, with HBRC, to help manage the potential ecological effects of gravel management in the braided rivers of the Heretaunga plains.