Integrated Catchment Management in Whanganui
The Whanganui River drains one of the largest catchments in the North Island, reaching deep into the central hill country before passing the city and meeting the sea. It is also a river recognised in law as a living whole, which makes a connected, catchment-scale view of water both natural and necessary here.
Soft river-terrace soils, erosion-prone papa hill country upstream, and flood-exposed land near the city all tie land use to river behaviour and water quality. LDE brings an integrated catchment view to the Whanganui and Manawatū area, combining surface-water and flood modelling, erosion and sediment assessment, and land-use and water-quality analysis within the freshwater policy framework.
We help councils, iwi and landowners understand how the catchment behaves from the hills to the coast, and plan for flooding, land use and freshwater health together. For Whanganui clients, that means catchment management that respects the river as a whole system, from headwaters to harbour.
How our Whanganui team delivers integrated catchment management
Catchment management in Whanganui works across a very large river system, from erosion-prone hill country in the headwaters to flood-exposed terraces near the city and the coast beyond. Our team models the catchment and its flood behaviour, assesses how erosion and land use upstream shape sediment and flow, and links that to water quality and the flood risk lower down, so the river is understood as one connected catchment rather than a set of separate reaches.
Bringing the surface-water, flood, erosion and land-use picture together is the core of the work, drawing on our wider integrated catchment management capability and our regional water experience across the Whanganui and Manawatū area.
- Catchment and flood modelling across the Whanganui River system
- Erosion and sediment assessment in papa hill-country headwaters
- Flood-hazard mapping on river terraces and low-lying land
- Land-use and water-quality assessment from the hills to the coast
Freshwater planning in the Whanganui and Manawatū area
Freshwater across the region is managed at the catchment scale by Horizons Regional Council, which sets the catchment limits, freshwater objectives and land-and-water framework, including the recognition of the Whanganui River as a whole, that catchment work has to align with. That framework follows national freshwater direction, so we anchor our modelling and assessment in the relevant policy and good practice.
- Ministry for the Environment and the National Policy Statement for Freshwater Management
- Water New Zealand good-practice guidance for catchment and stormwater management
LDE catchment management in the Whanganui and Manawatū area
LDE applies integrated catchment thinking across the Whanganui and Manawatū area, from the hill-country headwaters of the Whanganui River to the terraces and flood-exposed land near the city and the coast. With erosion upstream and flood risk downstream, much of our work is about modelling how the catchment behaves end to end and shaping land-use, flood and stormwater decisions so the river and its freshwater health are protected. You can see more of our regional water delivery on the projects page.
Common questions about integrated catchment management in the Whanganui and Manawatū area
Why take a whole-of-catchment view of the Whanganui River?
Because the river is one connected system, recognised as such in law, and what happens in the headwaters flows through to the city and the coast. Erosion, land use and flow upstream all shape water quality and flood risk downstream, so the catchment has to be understood as a whole.
How is this different from designing flood works on one reach?
Reach-scale flood design protects one stretch of river. Catchment management models the whole system, including the erosion and land use feeding it, and sets the flood and freshwater picture that local works fit within, so a fix in one place does not simply move the problem along the river.
Who leads LDE’s catchment work in Whanganui?
Chartered Professional Engineers and freshwater specialists from our team, supported by LDE modelling and planning specialists nationally.
How do headwater erosion and land use affect the lower river?
Erosion and land-use change in the hill-country headwaters add sediment and alter flow, which carries downstream to affect water quality, channel behaviour and flood risk near the city. We model that connection across the catchment and use it to target erosion control and land-use measures where they most benefit the river as a whole.
Whanganui / Manawatū
