London's geology is a patchwork of London Clay, River Terrace Deposits, and chalk. The clay shrinks in dry summers and swells in wet winters. This seasonal movement drives erosion along slopes and beneath foundations. Rain events are becoming more intense across the capital. The result is surface runoff that carves gullies and undercuts retaining walls. Our soil erosion analysis identifies these risks before they turn into structural problems. We combine field inspection with lab tests to quantify soil loss potential. This is critical for sites near the Thames or on the steep slopes of Hampstead Heath. A proper erosion study guides drainage design and slope protection. It also feeds into the wider estudio de mecánica de suelos needed for planning consent.
A two-week delay in erosion assessment during London's wet season can cost more in remedial works than the entire geotechnical investigation itself.
Scope of work
Area-specific notes
A common mistake contractors make is stripping topsoil weeks before earthworks start. Bare London Clay left exposed to autumn rain erodes fast. Within days, rills turn into deep gullies that undermine temporary works. Without a soil erosion analysis, the cost of re-grading and importing fill can blow the budget. Worse, eroded sediment clogs drains and violates environmental permits. The Environment Agency can halt the job. We've seen sites where a £1,000 study would have saved £20,000 in remedial earthworks. Don't let a preventable problem delay your project.
Standards used
BS 5930:2015 Code of practice for site investigations, Eurocode 7 (EN 1997-1:2004) Geotechnical design, CIRIA C753 The SuDS Manual (2015)
Linked services
Site Erosion Risk Assessment
Field walkover, soil classification, and RUSLE2 modelling to estimate annual soil loss. Includes mapping of erosion-prone areas and a prioritised action plan.
Laboratory Dispersivity Testing
Pinhole dispersion, double hydrometer, and chemical tests on London Clay samples to identify dispersive soils that erode rapidly in water.
Erosion Control Design Support
We specify erosion blankets, silt fences, check dams, and vegetative cover. Our recommendations align with CIRIA C753 and local planning requirements.
Typical parameters
Q&A
What causes soil erosion in London?
London's main cause is surface runoff on clay soils during heavy rain. The clay has low infiltration, so water runs off and carves channels. Steep slopes in areas like Sydenham Hill or the Lea Valley worsen the problem. Bare soil from construction or vegetation removal accelerates it.
How is soil erosion measured on a construction site?
We use a mix of field plots, erosion pins, and the RUSLE2 model. Field plots capture runoff and sediment in collection tanks. Erosion pins track surface lowering over weeks. The model predicts annual soil loss based on rainfall, soil type, slope, and cover.
What is a dispersive soil and why does it matter?
Dispersive soils have clay particles that detach in water and stay suspended. They erode much faster than normal clay. London Clay can be dispersive in some layers. If not identified, it leads to rapid gully formation and slope failure. The pinhole test tells us the dispersion class.
Do I need a soil erosion study for a small extension in London?
It depends on the site. If your extension is on a slope, near a watercourse, or on known dispersive clay, yes. Many London boroughs now ask for an erosion risk assessment as part of drainage or landscaping approvals. A quick desktop study often suffices for small projects.
How much does a soil erosion analysis cost in London?
A basic desktop assessment starts around £700. A full field and lab study for a medium site ranges between £1,200 and £2,000. Complex slopes or large developments may cost more. We can give a fixed price after a short site visit.