Dutch Water Defence Lines - UNESCO World Heritage Centre

Brief synthesis

The Dutch Water Defence Lines form a complete defence system that extends over 200 km along the edge of the administrative and economic heartland of Holland, consisting of the elongated New Dutch Waterline and the Defence Line of Amsterdam defensive ring. Built between 1815 and 1940, the system consists of an ingenious network of 96 forts, acting in concert with an intricate system of dikes, sluices, pumping stations, canals and inundation polders, and is a major example of a fortification based on the principle of temporary flooding of the land. Since the 16th century, the people in the Netherlands have used their special knowledge of hydraulic engineering for defence purposes. Each of the polders along the line of fortifications has its own inundation facilities.

The water level was a critical factor in the success of the Dutch Water Defence Lines; the water had to be too deep to wade through and too shallow for boats to sail on.

Because the Dutch Water Defence Lines have continually been adapted to the development of defence techniques and knowledge of hydraulics, they offer a complete and unique insight in a 125-year period of military water management in combination with fortifications. The extraordinary consistency of the Strategically Deployed Landscape, Water Management System, and Military Fortifications is still clearly visible. The New Dutch Waterline contains well-preserved, extraordinary water management structures, including the first fan sluice, a type of sluice that was later used worldwide. The Defence Line of Amsterdam includes forts that have an important place in the development of military engineering worldwide: they mark the shift from the conspicuous brick/stone casemated forts of the Montalembert tradition, in favour of the steel and concrete structures that were to be brought to their highest level of sophistication in the Maginot and Atlantic Wall fortifications. The combination of fixed positions with the deployment of mobile artillery to the intervals between the forts was also advanced in its application.

Criterion (ii): The Dutch Water Defence Lines are an illustration of an extensive integrated European defence system of the modern period which survived intact and well conserved since their creation in the beginning of the 19th century. They are part of a continuum of defensive measures that both preceded their construction and were later to influence some portions of them immediately before and after World War II.

Criterion (iv): The Dutch Water Defence Lines are an outstanding example of an extensive and ingenious system of military defence by inundation, that uses features and elements of the country’s landscape. The well-preserved collection of fortifications in the context of the surrounding landscape is unique in the European history of military architecture. The forts illustrate the development of military archi­tecture between 1815 and 1940, in particular the transition from brick construction to the use of reinforced concrete in the Defence Line of Amsterdam. This transition, with its experiments in the use of concrete and emphasis on the use of non-reinforced concrete, is an episode in the history of European architecture of which material remains are only rarely preserved.

Criterion (v): The Dutch Water Defence Lines form an extraordinary example of the Dutch expertise in landscape design and hydraulic engineering. They are notable for the unique way in which hydraulic engineering has been incorporated into the defences of the administrative and economic heartland of the country, including the nation’s capital city.

Integrity

The Dutch Water Defence Lines and their individual attributes are a complete, integrated defence system. They have not been used for military purposes since World War II and are formally out of operation since 1963. The characteristic openness of the inundation fields is preserved integrally in the parts of the Dutch Water Defence Lines where the pressure of spatial development was low after its military use has ended. The strategically deployed landscape is still well visible, but its extension is notably reduced and its degree of integrity is uneven. Especially, but not only, on the inner side of the defence lines, urban growth has often overwhelmed rurality and the visual relationships between the forts and the environment have been undermined. On the outer side, the side watched over by the forts, some new developments have occurred, and scattered buildings and groups of trees have modified the aspect of the landscape and the visibility of the “Prohibited Circles”.

The series of forts, batteries and ramparts make up a group of connected buildings in which the consecutive phases of military architecture are clearly recognisable. The range of hydraulic works and the military fortifications that supported the inundation system is a complete and mostly preserved entity, in mutual connection and in relation to the landscape. The water management system (a complex network of canals, dikes, gates, sluices) is still in use and its maintenance is assured as far as it is necessary for the safety of large cultivated and inhabited areas.

However, new developments and large infrastructures have already impacted upon the western portion of the Defence Line of Amsterdam, in the central portion of the New Dutch Waterline, and at the junction between the two, next to the cities of Amsterdam, Haarlem and Utrecht. There, fortifications, related ditches, canals and dikes have been preserved but the landscape has significantly changed, and several inundation fields are no longer as clearly recognisable as elsewhere. Nowadays these portions of the property are exposed to strong pressure for further transformation.

The effectiveness of the current actions of care and maintenance along with strengthened planning policies can secure the integrity of the property.

Authenticity

The Dutch Water Defence Lines still form a coherent human-made landscape, one in which natural elements such as water and soil have been incorporated into a built system of engineering works, creating a clearly defined military landscape. The military use has been terminated, but the landscape and built attributes are still present.

The physical attributes of the Dutch Water Defence Lines credibly reflect the Outstanding Universal Value through their form and design (the typology of forts, sluices, batteries, line ramparts), the specific use of building materials (brick, non-reinforced concrete, reinforced concrete), the workmanship (meticulous construction apparent in its constructional condition and flawlessness), and their reciprocal interrelations and relationships with the landscape setting (as an interconnected military functional system in the manmade landscape of the polders and the urbanised landscape). Although the military use and defence function have ceased, the primary agricultural use of the landscape has been retained alongside the introduction of recreational use.

Several sources exist that can demonstrate the authenticity of the property, including bibliographical and archival sources. The physical attributes reflect the values and the historic development of the property. Since the 1990s, maintenance, restorations and repurposing of the forts have contributed to maintaining near the main military structures the spirit of the military past of the defence line territory and made possible their sustainable use and access to the public. The military history remains tangible, because the story of the Dutch Water Defence Lines continues to be told in the area and through various media. However, the modifications to the landscape and the developments have, in some zones, reduced conditions of authenticity. 

Protection and management requirements

The legal framework for spatial planning, including landscape and heritage protection, is under reform in the Netherlands. From 01-01-2024, this new law will apply. The new Environment and Planning Act will more strongly and explicitly protect World Heritage.

Currently, World Heritage properties’ attributes and Outstanding Universal Value are given consideration at all national, provincial and local levels through the provisions of the Spatial Planning (General Rules) Decree, Dutch acronym Barro, issued in 2011, which identifies core qualities of the properties inscribed on the World Heritage List or included in the Tentative List. These qualities must be maintained or enhanced in plans and spatial developments. Specific rules from the Spatial Planning Decree stipulates that municipalities must consider cultural history when elaborating spatial plans.

The Barro provisions will be incorporated into the new Environment and Planning Act (01-01-2024), which stipulates that regulations for the preservation of the Outstanding Universal Value of World Heritage properties and the implementation of the World Heritage Convention must be developed.

In addition, all structures of the New Dutch Waterline are protected as nationally listed buildings, and the connection with the landscape is also protected through clustering of these structures. A number of built attributes of the Defence Line of Amsterdam are also protected as nationally listed buildings; the remaining built attributes in the Defence Line of Amsterdam are protected as provincially listed buildings. In all these cases, there is a licensing requirement for architectural and spatial planning developments for urban conservation areas, which is linked to the preservation of the monumental character, thereby complementing the protection afforded to individual heritage structures.

Further protection regimes afford protection to the setting of the Dutch Water Defence Lines. The municipal zoning plan has a legally binding force and is the key instrument for implementing protective measures.

Provinces are responsible for describing the ‘core qualities’ of existing or proposed World Heritage properties and for developing rules for their preservation. These rules are included in provincial by-laws and municipal zoning plans. The government and the provinces have the right to prepare government-imposed zoning plan amendments, as long as national or provincial interest is at stake, such as in the case of World Heritage or heritage preservation. These amendments have the same legal value as municipal zoning plans.

The rural zoning plan is the central instrument for the protection of the agricultural land and therefore of the inundation fields. Provincial by-laws prevent construction outside building locations identified by provinces, and agricultural land cannot be turned into buildable land. The application of sustainability principles also requires that urban developments must occur in existing urban areas. The necessity to deviate from this principle must be explicitly demonstrated.

Recommendations from independent experts are structurally enshrined in the process, both on the level of the World Heritage Site (spatial quality advisory team), the provincial level (provincial spatial quality advisor), and the local level (building aesthetics committee and listed buildings committee). Large-scale initiatives with a potentially large impact are subjected to a Heritage Impact Assessment. A strategic HIA of the relation to the World Heritage site is carried out in the case of potentially far-reaching developments, such as energy transition.

For highly dynamic areas it is key that the capacity of the property to accommodate potential developments is assessed through focused area analyses defining the specific conditions and locations for development that can support or enhance the integrity of the property and where this might pose challenges.

As per the Joint Arrangements Act, the four provinces of Noord–Holland, Gelderland, Noord-Brabant and Utrecht have signed a partnership agreement that establishes they act jointly as the site-holder through a single overarching management office covering the entirety of the Dutch Water Defence Lines. A small portion of the property falls within the Province of Zuid-Holland. The five provinces have agreed that the four provinces where the majority of the property is located look after the small section in Zuid-Holland. However, the Province of Zuid-Holland continues to perform its spatial-planning and protection tasks.

The site–holder office is managed by the four provinces under the direction of an independent Chair, with a representative of the Cultural Heritage Agency of the Netherlands as an advisor. The site-holder relies on the human resources of the Knowledge Centre of the waterlines, the independent Spatial Quality Advisory team. External support is also provided by the Cross-Waterline Entrepreneurship Foundation, which supports entrepreneurs in and around the property. The think tank Line Expert Team – 16 experts in 8 different subjects – is supported by two Provinces and offers expertise and advice to owners, managers and operators, including municipalities and water authorities.