Addressing Flooding by Improving UK Soil Health
My submission to the recent Flooding Bill consultation (via the House of Lords Rural Economy Research Group)
Exec Summary
• IE one of the main issues that stem from landscape wide degraded soil health
• The majority of the water in the channel came from the air
• Soil covers the land and the rain falls on that land
• All the water in open water features (rivers, lakes) should have passed through a soil phase
• Floodwater in channels is rain that fell on land upstream, and couldn’t get into the soil
• Rain water can’t get into the soil, so it runs-off and takes soil/nutrients (and farming productivity) with it
• If the water can’t get into the soil, there’s only one place it can go, off the surface, and downhill/down stream
Healthy soils solve flooding problems
• Healthy soils have infiltration rates 10/100x better than unhealthy ones, despite being of the same type (textural classification)
• Rain that infiltrates is diverted away from the flood peak, and will not enter stream flow for many hours, if not days, weeks or months
• Rainfall that infiltrates enters groundwater of some description
o Recharging aquifers, bore holes, well etc
o Continuously replenishing reservoirs, over time
• Rainfall that infiltrates maintains healthy stream flow (and water temperature)
• Rainfall that infiltrates is filtered (cleaned by soil/soil biology)
Small changes can have large benefits
• Most flood pulses are very shot-lived, perhaps only a few hours, but in that time, significant damage to property results along with all the muck and debris left behind in the streets etc. Hence extending out that pulse by just a few hours can mean the difference of a catastrophic flood (for affected residents) and a minor or inconsequential flooding event, or no flood at all
Preface
Working nationally as an independent farming consultant and trainer, supporting farmers, landowners and advisors in the adoption of soil health practices
A big part of that work is monitoring soils and pastures on Farm
Based on monitoring well over 250 farms right across the country work I’m now firmly convinced that poor soil health is currently one of the key threats to all rural economies in the UK
I truly believe that addressing soil health is THE most effective meanes of tackling flooding and water security issues at scale, while also delivering on farm productivity outcomes
Report
The key assertion here, is that poor soil health is manifesting as poor water infiltration, across all farming- and soil types.
By comparing infiltration rate tests in the field to an adjacent location, that is out of management, for example, a hedge or a verge, we’re evidencing differences in rates of infiltration of 10 or 100 times on the same soil type, even in the middle of wet winters
What manifests here, through the differences in management, is a change in the soil structure, related to the level of soil health present. Essentially healthy soils have good infiltration, and unhealthy soils have poor (or essentially) no infiltration.
It’s also meaning that land is lying wet for extended periods through our wet winters, significantly increasing winter housing and crop production costs – along with impacts on grain yields
While also leading to flashiness in catchments, with the accompanying turbidity, water quality and flooding issues, downstream
Improvements in soil structure here, mean fewer crops rotting off or needing to be resown and a lower grass weed pressure
While in the grazing context the data shows a strong correlation between increases in infiltration rates and increases in grass yield,
Fundamentally, flooding and water quality concerns are largely a surface water issue
The cause itself, as we see it, is the fact that the rain can’t get into the soil so it runs off and it takes soil with it, thus creating turbidity issues for example and making catchments flashy
Though no single class of interventions is necessarily mutually exclusive, once the water is in the channel we’re already playing catch up, we’re treating symptoms
The objective as we see it is to have the rain pass from that surface water phase and enter into a soil phase from which it then becomes a groundwater consideration
Once at this place water will be contributing to aquifer recharge, as well as reservoir recharge from groundwater
Water that does then find its way into the channel will then be cleaner and do so over protracted periods, essentially eliminating those flood pulses whilst contributing to an overall improvement in hydrology, taking the flashy ness out of the catchment,
And very much taking the pressure off existing and proposed flood alleviation works
And all with short lead times, data shows infiltration can be doubled in the first year
But critically we’re also divorcing ourselves from the traditional antagonistic relationship between productive and non-productive uses of land
Essentially the either or, mutually exclusive Framing with all the planning issues, compulsory purchases and resistance associated, instead moving towards synergies between nature-based solutions and improved productivity/biodiversity outcomes
Finally, As related to rural economies, and especially in the Uplands, I personally feel there’s a huge opportunity, through delivering on improved soil health, in other words regenerated natural capital, that this will translate to improved farm incomes and when scaled to the landscape scale, this has a very real potential to revitalize those economies, whilst also delivering on water quality, biodiversity and hydrology objectives
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