Part 4 - Where Do Nature-Based Solutions Work Best?
- Jonathan Cousins
- Oct 7
- 4 min read
Land Suitability and Risk Mapping
By Vision Consulting Engineers (VISION) • 7 Oct, 2025 • 4 min read
In This Article: - Why a data-driven approach is essential for choosing the right NbS for the right location. - How we use Multi-Criteria Analysis (MCA) and GIS to map catchment-wide environmental risks. - The key mapping outputs that identify priority zones for restoration. - The benefits of an evidence-based approach for project planning, funding, and community trust.
The Challenge
Not all land is suitable for every Nature-Based Solution (NbS) and choosing the right location and NbS type is essential for long-term success. We know from talking to the locals and reviewing catchment data that the issues in the catchment are complex and historic, so an adaptive and holistic method had to be developed specifically for this project. The aim was also to create a project blueprint for catchment restoration and flood risk reduction that can be applied at high-resolution across Northland and New Zealand.
Building a Baseline
Before starting a project, we need to ask the right questions and understand the baseline of the catchment, such as:
What is the history of the catchment, and what are the present conditions and future ambitions of the community?
Where does water flow overland during floods?
What are the slope, soil, and land use conditions?
Which soils are protected by vegetation cover?
Where are the steep slope erosion risks?
Where does high-energy water flow cause instream erosion in river channels?
Where are the main sources of nutrients and pathogens, and what pathways connect them to sensitive receptors like wetlands and rivers?
What has the community observed over time, and what has changed?
What’s already working or failing in the catchment?
What do the local community want?
Our approach in the Taumārere Project
As part of Phase 3 of the NbS Feasibility Project, we applied a Multi-Criteria Analysis (MCA) combining GIS mapping, hydrological analysis and modelling, and a range of spatial data including:
Slope maps to flag erosion-prone areas
Land use & forestry data to spot high-risk zones
Hydrological flow paths to track runoff
Soil/topographic layers for stability and infiltration
Hydraulic model layers to understand water forces in streams
Coastal floodplain & sea level rise maps for long-term planning
"Think of the MCA like a recipe, you add an amount of each data ingredient, combine them in processing, and hopefully what comes out is fully formed catchment management mapping tool. Of course, it isn’t always that easy, and many iterations were made and validated in the field using surveys and drone photography during significant weather events and flooding."
What Mapping Outputs Show for NbS Planning
We created multiple defensible and data-driven spatial layers showing us the following relative environmental risks and where NbS use might be possible - not guaranteed:
Steep Slopes Erosion risk
Instream Erosion risk
Nutrients and Pathogens risk
Combined Weighted Risk (combination of the above three risks)
NbS layers
Native Vegetation Planting
Steep Slope Erosion Control
Leaky Barriers (both raster and point based)
Silt Traps (both raster and point based including sizing traps)
Riparian Planting
Floodplain Reconnection
Wetland Restoration
Intertidal Wetland Restoration (phased expansion to the year 2130)
Prioritisation ranking of all mapped risks at sub-catchment scale for strategic planning
The following examples are outputs from the high-resolution Taumārere Catchment NbS MCA mapping. The examples show the range of landscapes that NbS opportunities have been identified in the project. As shown, the mapping highlights the "priority" restoration locations based on local conditions and available data. For instance, only the steepest and highly erodible hills within forestry blocks are recommended for erosion control.
Forward thinking and actions prior to tree harvest might focus energy on targeted wetland restoration in flatter land downstream that could provide an ideal sediment interception zone to capture dirty runoff during upstream harvest i.e., restoration would not specifically impact commercial forestry harvest, but could offer a layer of environmental buffering. Naturally, the hydro-ecological function of the wetland should be considered through design.
Phased Intertidal Wetland and Habitat Restoration Example
Looking at a specific local issue, such as declining tuna (eel) and īnanga (whitebait) habitats and the subsequent low recruitment numbers, can help focus the MCA GIS method, pinpoint possibly restoration locations, and think intergenerationally over the next century and beyond. The video below shows 4 predicted sea level rise scenarios (blue tones of shading) with climate change up to the year 2130 along with the red and yellow NbS classes 3 and 4 which represent the possible higher priority restoration sites.
As time progresses and sea level rises over the four phases, we see more land becoming exposed to coastal inundation during higher tides. The project goal might be to "get ahead" of the rise and provide space by migrating flood defenses and allowing habitats to form, rather than spending money on maintenance and infrastructure upgrades.
Thinking long-term has been essential to this project.
Benefits of mapping
Targets nature-based solutions to priority locations
Maximises return on investment by avoiding low-impact or unsuitable sites
Strengthens funding applications with robust, evidence-backed mapping outputs
Improves transparency so the community can see why certain sites are prioritised
Supports strategic planning at both property and whole-catchment scale
Builds trust by combining science with local knowledge in a clear, visual format
Explore the Complete Project:
This article is part of our five-part technical series on the Taumārere project. For a comprehensive overview, interactive maps, the full technical reports, and the project webinar, please visit our central case study hub.
Comments