Updated April 2026
A collection of resources to help growers make decisions about repairing, rebuilding or developing their soils following flood events such as Cyclone Gabrielle brought to much of the North Island. These events have happened before, and there have been lessons learned. We worked with our community of scientists and advisors to create a succinct set of materials support growers.
Much of the research and captured experience from Cyclone Gabrielle was summarised at a Research Symposium held in late 2025. The presentations, supporting material and videos of presentations are on our Cyclone Gabrielle Research Symposium pages.
Jump to the Cyclone Gabrielle Research Symposium and proceedings here>
Dealing with sediment covered paddocks?
Start here:
- FAR – Disaster Recovery Decisions: recommendations
This downloadable poster developed by FAR following Cyclone Gabrielle provides a decision guide to support recovery from a disaster. - Guide to regrassing flood damaged pastures – 2004 Decision Tree
Guidelines compiled immediately after Cyclone Gabrielle, from research after earlier flood events. Includes bullet points and the flow chart/decision tree developed after the 2004 Southern North Island Flood Event. - Block by Block Assessment template for growers
A simple template compiled by the Hawke’s Bay Vegetable Growers’ Association to ensure information is captured and a plan is made for each paddock or block.
Download our Cyclone Gabrielle Baseline Sampling Report here>
One of the best things to do is get plants growing. Growers are good at that. Plants will help draw water out of the soil, stabilise it and prevent dust blowing, and start to turn raw sediment into living soil.
In a nutshell
- Each situation is unique but principles apply
- Take time to breathe – plan, prepare, act for best results
- Know what the flood has done in your paddocks or blocks
- Did water cover the site for more than 3 days?
- Was the site scoured?
- Has sediment been deposited?
- Check your drainage – poor drainage will slow recovery
- Flood sediment is typically unstructured, with varying depths and textures
- Sandier where water moves quicker, clay where water ponds
- Nutrient status and pH variable, so soil testing and amendment helpful
- Soil drying rate depends largely on texture – plan around that for sowing drier first, wet last
- Anaerobic soil not good for seed, but cultivation will rapidly help
- Medium depth sediment (5 – 20cm) best cultivated to mix with topsoil below
- Deeper silt deposits (>20 cm) appear best cultivated when dried enough – lighter tractors preferred
- Surveys showed annual crops e.g. oats, ryecorn, annual ryegrass grew well
- Legumes can be beneficial especially in ongoing fertiliser applications not intended
- Mulching cover crops when mature may help build soil organic matter
- Think about the crops likely to planted when selecting species for covers
- Get something going as soon as sensible to avoid dry soil blowing and to start rebuilding soil structure.
Much of the NZ material available is based on research/experiences from the 2004 Southern North Island Storm Event. This was primarily based on re-grassing pastures, but much applies directly to horticulture and cropping as well.
Other Resources
More information for growers at Horticulture NZ website
For orchard information see Apples and Pears website
More regional information is available on Hawke’s Bay Regional Council’s website.
The Land Information aerial/satellite photo maps are here. Click the three white bars at top right to find more layers.
You can view flood extent via satellite imagery using the tool prepared by Reddy Pulanagari at Stoneleigh Consulting. Zoom in to find your places of interest. Click on Layers – top right to select different pieces of information.
We realise affected farms, orchards and vineyards have more than enough to cope with after such events. But if you can make a note of the sediment depth and type of sediment in any paddocks you are drilling, what operations you do, nutrients added and what seed you plant, we’re hoping that we will be able to collect and process information later. We want to add to the lessons from the 1948 Gisborne floods, 2004 Southern North Island Storm Event, and all the knowledge gained from Cyclone Gabrielle and responses.
Read these items first
FAR – Disaster Recovery Decisions: recommendations
Silt laden flood waters, roads and bridges gone, communications down, crops and income lost. It may be
some time before you can begin the physical clean up. Look after yourself and your people first. Then look after your business and look after your land. The chart offers guidance for making a start and returning to normal.
Revegetating cropping soils after a flood
Our 2023 notes and guidance of assessing deposits and planning the revegetation of flooded soils covered in sediment. Brought together lessons from earlier New Zealand flood events, how to manage areas with different sediment textures and depths. Includes the Decision Tree for determining best actions. Combine with Notes on species for flooded soil remediation to decide on what to plant.
Block by Block Assessment template for growers
This document prepared by the Hawke’s Bay Vegetable Growers’ Association is a recording sheet to ensure information is captured and a plan is made for each paddock or block. It is important to record relevant things, and this will help prioritise actions. File these carefully and refer back to them soon and in years to come.
Notes on species for flooded soil remediation
Look at Revegetating cropping soils after a flood first, then check out Merf’s thoughts on selecting seed to establish cover in silt covered paddocks. Spoiler: Don’t fret about species, include a few probably including annual grasses and legumes, get them on quickly before silt dries out and blows away.
Supplementary Information
Orchard Info – Tree survival post inundation
Condensed information for orchardists and other permanent crop growers.
Bullet points check for hazards, contaminants and sources. Get water off as soon as possible, clear trunks, disease management, soil nutrients and biology, get covers growing.
Silt damage decision tree
The decision tree will help you choose a response best suited to your situation.
Resources developed after the Southern North Island Storm Event of 2004. A very good place to start. There’s a flow diagram and some explanations. Largely focused on pastures. We’re working on resources with a cropping focus.
Silt and slip recovery 2004 storm report
Report of efforts to quantify and collate farmers experiences in re-grassing after 2004 storm.
Regrassing flood damaged pastures
Another article from the 2004 storm which suggests much of the sediment from this storm was reworked mudstone – the Hawke’s Bay material may be greywacke silts? Seedbed preparation appeared to improve establishment.
Silt recovery full report 2007
A 30 page scientific report with more detail. The information covers a range of slopes and situations, with some emphasis on grazing land.
Regrassing silt – technical document for rural professionals
Supports above information. Notes coarser sand laid nearer river lower fertility, finer sediments further away may be more fertile but variable so test. Flood deposits likely to need phosphorous, potassium and nitrogen.
Radio interview on silt deposits – Troy Baisden
Discusses geologic processes of silt creation and recycling through techtonics
Flood-Remediation-Factsheet-Queensland
Prepared by Growcom for growers in the Lockyer, Fassifern and Brisbane valleys in Queensland after flooding in 2011. Might be different soils etc., but good information worth reviewing.
Management Considerations for Post Flooding Soils
Useful item from Iowa State University, discusses soil changes when flooded for an extended period, including disruption to soil microbiology. Remember to take care interpreting overseas info.