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Complete a runoff and soil erosion risk assessment
The guidance on this page is for SFI pilot participants only. Please visit GOV.UK for the official Sustainable Farming Incentive scheme guidance.
Find out how land managers can complete a soil risk assessment to identify where they can reduce the risk of runoff, erosion and flooding.
If you’re completing this action as part of the Sustainable Farming Incentive pilot, how you do it is up to you.
The advice on this page can help you get better environmental and business benefits, but you do not have to follow it to get paid.
Reduce soil runoff and erosion
Soil runoff can carry very fine soil particles, nutrients, pesticides or manures to water bodies. This can cause pollution and harm water-based habitats. Runoff can move directly from a field into water, but it can also travel towards water in other ways, such as:
- through yards
- along tracks or roads
- via drains
Erosion removes topsoil and organic matter. This can:
- reduce crop yield
- lower surface water quality
- damage sensitive habitats
- cause flooding
Both water and wind can cause erosion.
You must complete a risk assessment if you’re using the:
- water body buffering standard
- improved grassland soils standard
- arable and horticultural soils standard
A risk assessment is also an important part of creating a soil management plan.
The risk assessment will identify:
- the risk of soil runoff and erosion
- water flow pathways (including field drains) to receptors including water bodies, sensitive habitats, roads and houses
- the potential for nutrient leaching or loss through field drainage
- land at risk of regular flooding
- fields where wind erosion occurs regularly
You’ll get most benefit if you can identify and reduce runoff and erosion on land:
- at risk of losing soil carbon or releasing greenhouse gases
- connected to wildlife habitats
- connected to water bodies
- with historic features
Do field assessments and take soil samples
You’ll need to find out soil type, depth and how water naturally drains through soil. To help with this you can:
- use a map and other resources from the UK soil observatory
- find your provisional agricultural land classification grade
Spring is often the best time to do field assessments and take soil samples.
Do field assessments
In the field you’ll need to assess:
- soil structure
- earthworm numbers
- soil compaction
- steepness and length of slopes
- visible signs of runoff and erosion
For guidance on field assessments, use:
- the thinksoils manual on assessing soil structure
- the Agriculture and Horticulture Development Board publications on how to count earthworms
Find out how to assess soil compaction.
Take soil samples
Take soil samples:
- when soil is not very wet or very dry
- before cultivation for planting
To find out soil organic matter you can send soil samples to a lab for analysis. This may also tell you the texture of the soil. Read a factsheet on how to assess soil texture.
Lab analysis will also tell you soil nutrient content. You can use this to make a nutrient management plan.
Identify historic features
You should identify any historic features as part of the assessment. Register and request an SFI Historic Environment Farm Environment Record (SFI HEFER) to learn more about historic features on your land.
How to complete a runoff and soil erosion risk assessment
To complete the risk assessment, you’ll need to look for signs of existing and historic erosion.
Record the risk assessment on a risk map or in a table. For each field area, record:
- inherent risk of erosion or runoff
- how it’s connected to water bodies, watercourses or sensitive habitats
- flood risk
- wind erosion
- the overall risk (very high, high, moderate or low)
Assess risk of runoff
Assess the risk of runoff based on the steepness of slopes, topography and valley features. In general, slopes:
- over 11 degrees may have very high runoff risk
- over 7 degrees may have high runoff risk
- between 3 degrees and 7 degrees may have moderate runoff risk
- under 3 degrees, including level ground, may have lower runoff risk
Assess past and present visible signs of runoff. For areas at:
- high or very high risk, record where you see runoff or ponding of water on the surface in most years during wet periods
- moderate risk, record where in some years you see some runoff in wet periods, and usually see runoff in very wet periods
- lower risk, record where you see runoff in very wet periods, but not every year
Record where runoff goes, on and off the farm. It can use gateways to leave fields and use roads as pathways. Record where you know runoff has caused problems in the past, such as flooding.
Assess risk of erosion
The movement of soil within fields causes erosion. Soil can be transferred to watercourses, into drains, or onto roads and neighbouring properties.
Assess soil erosion based on:
- soil type and texture
- the steepness of slopes, topography and valley features
For sandy and light silty soils, slopes:
- over 7 degrees may have very high erosion risk
- of 3 degrees to 7 degrees may have high erosion risk
- of 2 degrees to 3 degrees may have moderate erosion risk
- under 2 degrees, including level ground, may have low erosion risk
For medium and calcareous soils, slopes:
- over 7 degrees may have high erosion risk
- between 3 degrees to 7degrees may have moderate erosion risk
- under 3 degrees, including level ground may, have lower erosion risk
While heavy soils may have a lower erosion risk, your risk assessment may show they still have a risk of runoff.
Assess past and present visible signs of soil erosion, like rills (small streams) and gullies. Record where they occur, and how often.
Record soil erosion risk for each field area. On very high erosion risk areas, look out for rills and gullies that form in most years in wet periods.
On high erosion risk areas, look out for rills that form in most seasons during wet periods.
On moderate erosion risk areas, look out for rills developing in some seasons during very wet periods. On both moderate and low risk areas, look for soil you see being deposited onto roads or into watercourses, ditches and sensitive habitats.
Assess flood risk
Land that floods can be prone to erosion and runoff, particularly when under cultivation.
You should record land that floods at least once every 3 years as high risk in your assessment.
Assess risk of wind erosion
Wind erosion is most likely on fine sandy soils and light peaty soils. It will be worse in dry conditions or where there is drainage, bare land or fine dry seedbeds.
Signs of wind erosion include:
- drifting soil
- buried seedlings
- soil blown into hedgerows and ditches, and onto nearby roads
You should record land where wind erosion occurs at least once every 3 years as high risk in your assessment.
Assess risk of nitrogen leaching
Light sandy and shallow soils are less able to store nitrogen. It can be easily lost as water filters through the soil. Light and sandy soils include:
- sand, loamy sand or sandy loam to 40cm depth
- sand or loamy sand between 40cm and 80cm
- over sandstone rock
Shallow soils are:
- soils over impermeable subsoils
- soils where the parent rock (chalk, limestone or other rock) is within 40cm of the soil surface
On light and sandy soils, record where nitrogen leaching will be a risk.
Record each area of risk
For each field or field area, record a risk level of very high, high, moderate or low. If the risk is different within a field or between fields, for example due to changes in soil type or slope, record the risk of each area separately.
Where there’s little or no connection between the area and the nearest receptor, such as watercourses and sensitive habitats, the inherent risk of pollution will be less. Use your own knowledge, experience and judgement to upgrade or downgrade the risk.
The risk of erosion or runoff also depends on other factors such as:
- poor vegetation cover over winter due to late harvested crops and late establishment of winter cereals or grass reseeds
- compaction caused by livestock or vehicles
- low soil organic matter resulting in a poor soil structure, and less water infiltration
- long unbroken slopes of 150 metres or more
- land features that concentrate flow, like valleys and gateways
- poorly maintained or blocked drains
How to use a runoff and soil erosion risk assessment
The risk assessment will help identify where you can manage land for the:
- water body buffering standard
- improved grassland soils standard
- arable and horticultural soils standard
Update the risk assessment every 2 years for the arable and horticultural soils standard and the improved grassland soils standard.
You can also use the assessment in a soil management plan. This can help you improve soil health to benefit both your business and the environment.
