Coastal Erosion and Land Cover Monitoring

Near the village of Wierum, on the Frisian coast of the Wadden Sea, a salt marsh meets the open tidal flats. Whether that marsh edge grows seaward or retreats tells coastal managers a great deal: salt marshes damp incoming waves, trap sediment and form a natural first line of defence in front of the dikes that keep the land behind them dry.

Together with Rijkswaterstaat and Lumax AI, we built CODAP, the Coastal Data Portal: an end-to-end monitoring pipeline that turns repeated drone surveys of this coast into maps of land cover and elevation change, and serves them on an interactive web portal anyone can explore in a browser.

Why this coastline matters

The Wadden Sea, a UNESCO World Heritage Site, is the largest unbroken system of intertidal sand and mud flats in the world. Its edges are working landscapes as much as natural ones.

The monitoring challenge

Watching a coastline change sounds simple. Doing it rigorously is not. Tap each challenge to see why.

From drone flights to a living map

Every few months, a drone surveys the site and the imagery is processed into two precise products: an orthophoto, a distortion-free aerial image of the whole site, and a digital elevation model that records the height of every point on the marsh and flats.

A semantic segmentation model then classifies the orthophoto pixel by pixel into coastal land cover types such as intertidal mud, salt marsh vegetation, macro algae, shells and the built surfaces of the sea dike, following a 16-class annotation scheme designed with coastal ecologists. The predictions, orthophotos and elevation data are published as map tiles that the CODAP portal streams straight to the browser. No GIS software needed, just a link.

Comparing surveys through time

The heart of the portal is comparison. A timeline slider picks any two flights, and three view modes make the differences jump out: a swipe handle you drag across the map to reveal one date beneath the other, a side-by-side split view that pans and zooms in sync, and a single mode for studying one survey in depth.

Measuring erosion, centimetre by centimetre

Land cover tells you what the surface is; elevation tells you where it is going. By differencing the elevation models of two flights, the portal computes a change map of the entire site: blue where sediment has accumulated, red where the surface has eroded, at centimetre resolution.

Patterns that would take years of ground surveys to establish become visible at a glance: the flats in front of Wierum are accreting while a narrow band along the marsh edge erodes, the kind of insight that directly informs where protection or restoration effort should go.

The impact

CODAP turns coastal monitoring from an occasional, labour-intensive campaign into a routine: fly, process, publish, compare. Every survey lands in the same portal, classified the same way, comparable with every survey before it. Coastal managers at Rijkswaterstaat can watch the marsh edge evolve at centimetre precision without leaving their desk.

Wierum is only the beginning. The portal was built multi-site from day one, and we intend to expand it to more sites along the Wadden Sea coast and to coastlines in other countries: the same pipeline of fly, map, classify and compare applies to any shore a drone can survey.

The bigger idea is preparedness. As sea levels rise, decisions about where to reinforce dikes, restore marshes or let nature take its course all depend on knowing precisely how each stretch of coast is responding. By making that evidence continuous, affordable and easy to read, CODAP helps coastal communities prepare for and adapt to the rising sea rather than react to it.