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What this layer is
LiDAR — Light Detection And Ranging — is airborne laser scanning. From an aircraft the sensor fires millions of pulses per second, records where they hit and how long they took to return, and produces a cloud of 3D points covering every square metre of ground. Clever filtering then separates out the returns that came from trees, buildings and overhead wires, leaving a bare-earth model — the shape of the land itself.
The Environment Agency has now flown the whole of England at 1-metre resolution, and the data is freely available as open data. At that resolution you can see the edge of a ditch, the profile of a bank, or the slight hollow of an infilled pond. Vegetation is literally invisible — which is exactly the point.
What it reveals in this catchment
The Upper Medway is ghyll country: a landscape of small, steep, incised streams cutting down through sandstone and clay. LiDAR shows this network in almost shocking detail:
- Every ghyll. Including the small ones that do not appear on the OS map because they flow under tree canopy. Their headwaters — where restoration work can be most effective — are immediately visible.
- Historical water management. Old mill leats, hammer ponds (the Weald was England's iron industry for centuries), stewponds, and drainage ditches all show up as subtle earthwork features.
- Flood-prone areas. Low-lying ground that will flood in extreme rainfall, and the shape of the floodplain that will actually do the attenuation work.
- Field drainage patterns. Ridge-and-furrow, surface-water collection hollows, hedgerow banks, trackways — the physical infrastructure of past farming, much of it still doing useful work.
- Ancient banks and boundaries. Parish boundaries, medieval assart banks, deer park pales — archaeology in plain sight.
What land stewards can do with this
- Slow the flow. The pattern of ghyll headwaters shown by LiDAR is exactly where natural flood-management interventions — leaky dams, scrapes, wet-woodland creation — will have the largest downstream effect for the least disturbance.
- Restore lost ponds. Infilled ponds still show up as shallow hollows in the LiDAR even a century after they went. They are almost always easier and cheaper to re-excavate than to dig new ones elsewhere.
- Plan woodland creation. Steep slopes visible in the LiDAR are usually better kept as or converted to woodland; gentler ground is productive for other uses. Matching land use to slope is fundamental regenerative design.
- Find what you already have. Most holdings contain at least one historic feature that the LiDAR surfaces — a lost pond, a grown-over track, a bank the owner didn't know was there. The first survey of your own farm with LiDAR is often revelatory.
Data source: Environment Agency National LiDAR Programme — 1-metre Digital Terrain Model (DTM) open data. Hillshade, slope, flow-accumulation and pond-detection derivatives generated by the cluster's ecology platform. EA open-data licence.