Causeways and soil

Roads are usually built on the existing land surface, but sometimes a road needs to go through difficult areas. The answer may be to build a causeway. These are normally cheaper to construct than a bridge.

A causeway is a raised stretch of road or track which has been constructed, often through marshland or water, but also sometimes where a higher track is needed for other reasons. Here are a few examples:

Linking offshore islands

Causeways are sometimes built to join an off-shore island to the mainland, or from one island to another. Some of these links are very ancient. At Maldon in Essex a causeway links Northey Island to the mainland and it was here in the year 991 that a battle took place between Viking raiders who had camped on the island and the local Saxons, led by Byrhtnoth. If the causeway had not been there, the result of the battle - which the Saxons lost - might have been different. A similar causeway links Holy Island (Lindisfarne) to the mainland in Northumberland, though the metalled surface was built much later. This 3-mile-long causeway is covered by the incoming tide and so is only passable at low water.

Crossing marshy land

When a road has to cross swampy, wet land, the best way is usually to construct a raised causeway. In ancient times this was done using a series of large timber posts with a planked top surface. It has been possible to study the techniques used since the remains of several such roadways have been excavated in Ireland, Denmark and elsewhere. The wet peat has proved ideal for preserving the timbers which can be conserved and dated scientifically. One example is the Ravning Enge Viking causeway in central Jutland, as seen in the accompanying photos here.

Dealing with sand

In sand dune or dune heathland areas, a causeway is sometimes built partly to keep the roadway free of blown sand but also because the area can be marshy. Here is one example showing the road along a long sandy stretch of the west coast of Jutland, where considerable lengths of the road are causeway.

Crossing a field

This raised causeway stops tractors ploughing through a public right of way.