A project drawing busloads

A row of touring cars, on a dike in a green polder landscape. Groups of Asian tourists stretch out their arms to take snapshots of the tree-lined farmhouses. Visitors from all over the world visit the Overdiepse Polder, near Waalwijk, to see for themselves just how those clever Dutchmen deal with the rising waters.

Admittedly, what the inhabitants of this polder have pulled of is a strong feat of Dutch inventiveness. Go figure: in 2006 they were told that their native soil would be ‘de-polderised’. The aim of this intervention was to provide breathing space for the river Berghse Maas, and enable it to run its banks and offload excess water. The local agricultural entrepreneurs put their minds together and came up with a ‘terpenplan’ (mound plan), to be able stay in the polder even during floods. Which, by the way, is not something to sit and wait for anxiously every day. It will probably occur only once every 25 years.

Different words, same principle

Keeping your feet dry: an art that inhabitants of the Low Countries have mastered for at least a millennium now. Dikes are the more familiar method, but ‘terpen’ (mounds) are also very effective. Etymologically, the word ‘terp’ is a Frisian variant on the word for ‘village’. But there are also ‘huisterpen’, or house mounds, raised for one farm and its outhouses only. Most of these smaller mounds were raised after the year 1000. At that time, many farmers left the village mounds for a more private place in the open landscape.

Similar artificial elevations scatter the Dutch landscape from the Wadden in the north to Zeeland in the south, but with different names, such as wierde, woerd and (w)erf. “So many types of terp, one more won’t do any harm”, we thought. With the only difference that our type will be a modern, 21st century mound.

A sense of rhythm

What interventions made the Overdiepse Polder futureproof? Well, the existing dike around the polder has been lowered, and further inland a new dike has been raised. Along this dike, eight separate mounds with a height of six meters have been created, for eight farms. These mounds guarantee the continuation of the double function of the area (water management and agriculture) into the future.

Inspiration for the design of this new mound landscape was taken from Dutch historical examples. Vital details are the uniform planting, the positioning of buildings and the way the mounds are fitted to the dike. This fit was optimised with an innovative concept of upper and lower mounds.

All eight mounds have a similar structure and landscaping, to create spatial cohesion. Distances between mounds are the same throughout, and each mound sits in an elegant curve along the dike, ending at the bend of the Bergsche Maas. The result: a uniform string, rhythmically placed in a line that befits the underlying historical landscape.

Smart solutions: two mounds in one

Each mound consists of an upper mound and a lower mound. As such, the upper mound remains separate from the body of the dike. And it leaves enough space between perimeter planting and buildings, without sacrificing any work space.

Room for the river

Worldwide, the climate is changing. The Netherlands will definitely be affected: an increase in rainfall and rising sea levels will have to be dealt with. As a result, Rijkswaterstaat decided in 2006 to step up flood protection for the Dutch river system. Thirty-nine projects were listed under the national program ‘Ruimte voor de Rivier’ (‘Room for the river’). One of these projects was the ‘de-polderisation’ project of the Overdiepse Polder. Together, the thirty-nine projects increase water security for up to 4 million people.