Distributed among different categories of more or less strong protective measures according to its architectural, historical, or cultural interest, the French heritage is faced with processes of erosion, which seem to be irreversible. Among the principal causes that can be put forward are the decaying of materials, the physical or chemical wear and tear on fabric - both traditional and modern - where effects are quantitatively and qualitatively accelerating, induced by causes which seem more and more difficult to curb and control. Equally important causes of decay are clumsiness and misunderstanding, but also criminal intent, stupidity or lack of knowledge. These impact on a limited basis as well as with development projects and at the level of urban development.

To counter these effects, the State, public authorities, and associations dealing with conservation have set up a series of regulatory measures including financial assistance, professional training, publicity and education. These measures are generally effective and contribute to a decrease in the pace of decay, but they nonetheless remain insufficient, particularly for certain categories of heritage such as vernacular, military, industrial, or 20th century heritage. The challenges include the movement of people away from rural areas, economic decline, as well as misunderstanding or lack of knowledge.

Generally speaking, the most devastating causes of alteration to all types of built heritage are development and re-use programmes, because of a complete absence of methodology and ethics. First and foremost, one has to recall the catastrophic effects of façadism, which, by relegating heritage to a theatrical set-up, empty it of its architectural and cultural meaning.

One must also condemn the increasingly more pronounced and devastating effects of standardisation applied to heritage for varied reasons such as safety of the public, regulations on trades, tools, and materials that eradicate traditional crafts know-how, and eliminate heritage as a cultural expression.

The recognition of the architectural heritage as a valuable representation of our cultural heritage and identity increasingly appears as a necessity if we want to save it, and as a prerequisite to the establishment of an efficient and decisive policy.

Yet there are examples which do not fall into these categories and whose scale go beyond every day action. The year 2001 in France was marked by two cases, among others, that were particularly striking, and these are discussed below.

The Flooding of the Somme Valley

In Picardy, the Somme Valley contains true architectural jewels, particularly from the Gothic era and the beginning of the Renaissance, of which it holds tens of the most remarkable examples. In Spring 2001, the valley was afflicted by very serious floods that impacted 125 municipalities and affected between 1500 and 2000 houses, causing considerable upset to the people and the local economy. About 20 of the more remarkable historical monuments were touched:

  • 15 churches and monastery foundations

  • 5 walled units

  • 2 factories and industrial heritage

  • 1 megalith.

At the initiative of the Regional Conservatory of Historical Monuments, the protected heritage has been put under observation since August 2001. A mission was entrusted to the Architect in Chief of Historical Monuments, who assessed the damage caused by the water saturation of the soil and the structures:

  • weakening of sub-soil and layers supporting the foundations;

  • increased fluids upwelling through capillary action in masonry, dissolving of mortars, and potential weakening of the structures;

  • salt migration, acceleration of chemical alteration of the materials;

  • risks of alteration of works of art, murals, and furniture.

The damage observed at the highest levels of flooding may be aggravated when the water levels decrease by complementary phenomena such as:

  • leaching of geological layers by the water’s ebbing;

  • soil retraction (clay and marl) and destabilisation of foundations.

Urgent interventions were prescribed, which unfortunately were not followed: this causes some concerns for the preservation of the edifices. More alarming yet is the fact that the phreatic tables are still saturated, and that the hydraulic works that should help evacuate the waters are still not yet ready, which constitutes a serious threat should there be a recurrence of flooding in the next damp season. The level of risk for heritage might be catastrophic.

Montagne de Laon

Around 120 kilometres north of Paris, Laon is perched on top of a narrow hill of about 70 hectares, which rises to a height of 170 metres above the surrounding plain. Settled since Roman times, the ‘upper town’ developed during the Middle Ages, sheltered by its surrounding walls. The remaining part is an outstanding urban ensemble including the Cathedral, a jewel of Gothic architecture of the 12th and 13th centuries.

The geological layers that support the upper town are composed of a stratification of sands, set over limestone layers under which lie sands again and a clay deposit: these different geological layers were quarried for the construction of the town, which created a large system of quarries, galleries and cellars, on several superimposed levels. The operation of the quarries started slowing down during the 16th century.

During the 19th and 20th centuries, the increasing urbanisation, coinciding with a progressively diminishing surveillance, caused the beginning of a decaying process of the underground layers. Until recently, this system was placed under the surveillance and regulation of the police, and under the responsibility of the municipal services.

The uncontrolled evacuation of the pluvial water has been added to by the considerable increase of domestic uses of water (up to 100 times within 50 years), which discharges directly into the geological layers of sands and soft clay, affecting their resistance. It must be remembered that the numerous underground systems are walled up and their condition is completely unknown: one is entitled to fear circumscribed collapses or a general landslide of the limestone layer.

The consequences have already been identified. The Gothic Cathedral, one of the major masterpieces of early Gothic architecture, has experienced localised failure of the foundations, with the risks of repercussions on the vaults, the superstructures, and the general stability.

On the walls of the upper town (14th-15th centuries) observations are made of more and more frequent and significant collapses. In addition, effects are visible on the most important buildings of the upper town (Old Bishop’s palace, the law courts) and other churches and chapels, as well as in the historical town, covered as a protected zone.

It is recommended that a multi-disciplinary survey be urgently launched that includes geologists, archaeologists, architects of the Historical Monuments Department and (BET) the research consultancy in charge of prospecting. It is most urgent to gain an exact knowledge of the soil and the galleries: their number, position and level; their condition and the rate of decay of the geological layers. As well, we must identify the urgent steps to be taken until definite measures can be identified, financed and applied. We remain aware that numerous excavations date back to the Middle Ages and thus will also represent a major interest in relation to the history of the quarrying techniques.

The rescue of the hill of Laon is a major, national project, which calls for strong and urgent action.