Short Virtual Presentation & Digital Poster 10th Australian Stream Management Conference 2021

Steps towards incorporating geomorphic considerations in farm and catchment management plans in the Waimatā Catchment, Aotearoa New Zealand (#58)

Khendra Harvey 1 , Gary Brierley 1 , Jon Tunnicliffe 1
  1. School of Environment, The University of Auckland, Auckland, New Zealand

Why the work was done

Recurrent log accumulations on beaches reflect pronounced connectivity from the Mountains to the Sea on the East Cape of Aotearoa. This study develops tools to support the development of catchment plans to manage geomorphic processes and connectivity relations in these river systems.


What work was done?

Field investigations, landscape mapping and modelling analyses derive geomorphic understandings to support co-development of scenarios to scope restoration initiatives with members of the Waimatā Catchment Group. 


What was learnt?

High sediment yields in headwater reaches, and efficient sediment delivery pathways, create sedimentation issues in lower reaches of the Waimatā Catchment. Overall, this river behaves like a flume, efficiently conveying flow, sediment, and logs through terrace-confined reaches. Local transfer reaches have high capacity for adjustment, while throughput reaches readily flush sediments to the coast.

Connectivity modelling shows how land use influences the potential for sediment generation and transport, with high connectivity in steep slope and low vegetated areas and low connectivity in low slope or densely forested reaches. Options for management of sediment ‘hotspots identified using a Connectivity Index are developed using the CASCADE Toolbox. 


Why this work matters

Unless geomorphic considerations are incorporated into catchment management plans, prospects for restoration initiatives are unlikely to be effective. Efforts to manage sediment problems at source in this highly connected river system carefully link forestry activities with farm management plans in a catchment scale sediment management plan.

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