Research project

What happens to a river, and its people, when its sand is taken?

Sand is the second most used natural resource after water, and much of what it costs is hidden: beneath the river surface, along eroding banks, and in the lives of the communities who live beside it. HIDDEN SAND brings together physical surveys, simulation, community knowledge and socio-economic data, and uses digital tools to educate people and inform policy, starting on the Mekong in Cambodia.

Aerial view of a wide river at sunrise, with sandbanks and boats
A great river, and the sand it carries.
Wooden boats moored on the river at dusk, with a city skyline behind
People live and work along the river.
A sand barge and a heap of dredged sand at the river's edge, with a city skyline beyond
Sand is dredged from the river bed...
A dredging barge pumping a plume of sand
Sand is dredged from the river bed...
Aerial view of sand barges on the river
...and carried away by barge...
Reclaimed land beside a city skyline
...to build cities and reclaim land.
A barge beside an eroding river bank with houses above it
Banks erode, and homes are put at risk.
A person in a hard hat looks over a river bank whose edge has been cut away
Surveys and monitoring show how the river is changing.

Below the surface

Sand is a budget

A stretch of river holds its shape only while the sand leaving it, downstream and in dredgers' holds, is replaced from upstream.

The effect is not where you dig

Pits trap the sand passing through. The water leaving them picks up more from the bed, so the lowering spreads across the channel and downstream.

The banks pay later

As the bed drops, banks stand taller and become less stable. Dredging mid-channel can look safe for years, then stop being safe.

Beside the river

Livelihoods and communities

Extraction changes who earns, who loses land and how riverside life works. We record household economies, changing livelihoods and the costs communities bear, alongside the physical measurements.

Sand stories and journeys

People share their own accounts of the river, and we follow sand from the bed to the building and reclamation sites it ends up in, so benefits and costs can be seen along the whole chain.

Digital tools for policy

Surveys, models, monitoring and community testimony become simulations, maps and an online exhibition that help people understand the problem and help decision-makers act on it.

We look at sand through five lenses: materialsocio-economicculturalenvironmentalglobal

Houses along the water's edge beside a city
Homes along the water's edge.
A small home on the water, with a city skyline beyond
A home on the water, with the city beyond.

Explore the data

Maps and 3D views built from satellite detections, multibeam surveys and community observations.

Map of the Phnom Penh area with candidate sand-infill sites Digital twin

Sand budget tool

One map for budgeting and managing sand on the lower Mekong: inland sand infill from Landsat, Sentinel-1 vessel detections, extraction risk by river reach, population and asset exposure, and community observations you can add from your phone.

Open the tool ↗ Hexagons coloured by the density of vessel detections along the Mekong Monitoring

River vessel monitoring

Sentinel-1 detections of the vessels working on the river, by hexagon, by day or by river reach, with a comparison of any two areas. Opens the sand budget tool on its Vessels tab.

Open the vessel viewer ↗ Satellite image of the Roka Koang reach in 3D with the surveyed pits marked 3D visualisation

Dive into a sand-mining pit

Fly over the Roka Koang reach, then dive through murky water to the real multibeam bed. Stand in an 11.8 m deep pit beside a truck and a building to see how big the hole is.

Open the 3D viewer ↗

Try the simulations

Conceptual models, not calibrated to real Mekong transport rates: use them to build intuition.

Plan view of a 10 km river reach with sand waves and dredging pits Simulation

Dredging impacts simulator

Paint a dredge area on a 10 km river reach and watch pits spread, the bed lower and the banks approach failure, in plan and in 3D.

Open the simulator ↗ Cross-section of a riverbank made of thousands of soil particles Simulation

Bank erosion simulator

A particle simulation of a riverbank failing by rotational slump after drawdown, heavy rain and erosion at the toe.

Open the simulator ↗

In development

Simulation

SAND SIM

The project's full sediment-transport simulation of how sand moves through the river system.

Open SAND SIM ↗ Exhibition

Virtual exhibition

Walk through the project's findings and the story of the river, online.

Enter the exhibition ↗