How did glacial meltwater create spillways across northern Europe?

During the Pleistocene Epoch, the North European Plain was shaped by repeated glaciations that left behind a complex postglacial landscape. As the massive ice sheets advanced and retreated, they deposited moraine in great arcs across northern Germany and Poland.1

The spillways were created as glacial meltwaters flowed toward the sea, moving parallel to the stationary edges of the ice front. These channels were carved and subsequently filled with sand and gravel transported by the rushing glacial streams. Because these streams were often laden with debris, they deposited significant amounts of glacial outwash along their paths.12

Today, these ancient spillways are recognizable as long, parallel features across the landscape, typically occupied by flat, poorly drained wetlands. While these areas were once vital conduits for meltwater, they are now relatively unproductive for agriculture compared to other parts of the plain.1