Disastrous floods that hit a large area of the Czech Republic in August 2002 unfortunately did not spare the archives, libraries, museums, galleries and other cultural institutions either. Damage to cultural heritage was unprecedented and it is therefore useful to describe in detail the situation immediately after the water receded.

When the buildings were secured and the initial static survey was carried out the archivists assessed the damage. Documents were divided into three categories according to the extent of damage.

Records in the First group were those from flooded depositories that remained above the water level. They did not suffer direct damage, but were exposed to almost 100% humidity for about a week. These materials were just slightly damp and after they had been transferred they were air dried. Prague City Archives (AMP) used the empty depository rooms in the new archive building in Prague 4 for that. The ventilation system helped to adjust the environment in the rooms by reducing the relative humidity of the forced air to the lowest possible level (recommended optimum moisture content for a long-term storing of archive materials is around 55%) and by slightly increasing the temperature up to about 20°C (recommended temperature is between 15-18°C in standard conditions). For the sake of interest : 24 hours after the records had been moved in the relative humidity in the depositories increased up to 80%. Mould growth which generally represents greatest danger to the records irrespective of whether they were exposed to water or not affected only 10% of records. A suggested method of eliminating mould growth was disinfecting with 2,5-5% solution based on quaternary ammonium salts, e.g. a disinfectant sold under the Czech trading name Ajatin. The affected parts should be sprayed or coated by the substance.

Second group comprises records affected by water, but in a considerably good physical condition. Those were records that remained in boxes on the shelves and were “just” wet and slightly soiled. These records were – where possible – rinsed by clean water and placed in numbered containers that were immediately transferred by refrigerator vans to be deep-frozen. This procedure was used successfully after similar natural disasters in other countries and its aim is to stop the process of biological decay which would in a very short time cause physical destruction of documents. It is necessary to realise that the warm weather in August initiates mould growth spread in 24-48 hours.

The third and last group of records were those that suffered also physical damage. The records storage boxes and pieces of furniture lay scattered on the floor, sheets of paper were torn and everything was covered in mud. Unfortunately, these documents had to be sorted according to their value and degree of degradation. Some of them were also deep-frozen as were the documents from the second group. In some cases it was obvious that the restoration is impossible or would be costly and time demanding and thus disproportionate to their documentary value. Therefore they were discarded and shredded.

Before the restoration of records started it was necessary to carry out a study in the shortest period of time to compare available drying methods and assess possible risks they represent for the de-frozen documents. Conservation centre of the State Central Archives in Prague (now called the National Archives) and the National Library in Prague became guarantors of this task. Some important conclusions ensued from this study and from experience :

• Lyophilisation and vacuum freeze-drying methods using special lyophilisation and vacuum appliance are suitable for all types of archived materials. It is however very labour-intensive, time-consuming due to limited capacity of the appliance and costly. Under the given conditions the method is more suitable for more valuable records that are to be archived for a longer period of time.
• Method of humid warmth drying in special drying chambers used for different purpose, e.g. by woodworking industry, is suitable where fast drying of large quantities of materials is required, however it degrades their mechanical properties. This method can be recommended only for records where a long-term store is not expected.
• Microwave drying can be used – similar to the previous method – only for materials with limited l lifetime. This method is also relatively slow.
• Air drying is a very considerate method. For some types of records only this method can be applied, e.g. for parchments or leather binding. Disadvantages are considerable labour and space demands.

Based on the assessment of the methods and considering the actual situation the AMP decided to use the last method of air drying. The work was commissioned to a professional company that collected the records from refrigeration plant and transferred them in their own refrigerator vans to the company’s workshop. There the records were placed in a room with the temperature of 21°C and stored first in perforated boxes to ensure free air circulation. After 6 hours it was possible to separate individual documents in the package from each other without causing damage. Materials soiled with mud and sand were rinsed with clean water 18 – 21 °C warm. Separate pages of de-frozen documents were sprinkled with disinfecting Ajatin solution and then spread one after another on strips of cardboard in their original logical arrangement. Continual removal of excess moisture content was ensured by the use of dehumidification appliance. The length of drying process depending on the type of document was between 4 – 24 hours.

After drying the materials were transferred to the archives premises in Prague-Chodovec for final disinfecting. The AMP uses a disinfecting chamber with the volume of 4 m3 and daily capacity of 10-12 running metres of records for treatment of materials stored in unfavourable conditions (not only flooded ones). Disinfecting is done by gas sold under trade name Etoxen (10% of ethylene oxide and 90% of carbon dioxide). Finally the records were handed over to custodians who decided about further steps to be taken. A small amount of the most valuable records was forwarded to the archives conservation centre for treatment. Most of dried records were rearranged by the custodians according to the archive rules, placed in protection covers and stored in new depositories.

Only one out of 8 buildings occupied by the AMP in 2002 was hit by the floods – a small depository in Prague – Holešovice district. It is situated right at the Vltava riverbank. When the river culminated the water level reached the 1st floor of the building. Total of 406 containers with records directly hit by the flood (200 running metres) were transported to refrigeration plant. They were dried and then disinfected and stored. The archives building in Prague – Holešovice district was assessed as unsuitable for the archives purposes and was handed over to the City of Prague for further use.

About 5% out of 16 km of materials in custody of the archives had to be moved into new premises, less than 1,5% was directly damaged by the flood. Most of the damaged materials were of less documentary value. However, more than 1,5 million Czech crowns had to be allocated for their recovery.

Naturally, it was not possible to recover the records as they were before the flood. Paper was distorted and often torn due to the movement caused by the flood as well as following handling. In some places ink was run, but not to the extent expected by the archivists. Most of the seals were run, contrary to that the condition of typed and printed texts was relatively good.

It is necessary to say that some other archives were in much different situation – their records suffered serious damage. It was among others the Architecture Archives of the National Technical Museum in Prague (unique designs of modern Czech architecture on tracing paper and paper models were damaged), Central Military Archives (documents about World War II), Archives of the Academy of Science of the Czech Republic (library, estates of prominent scientist, photographs), National Library in Prague (19th century prints) etc. Most of flooded documents from Czech archives totalling almost 2.000 m3 were deep-frozen and have currently been recovered.

Thanks to relatively limited damage of our archives we were able to provide active help to other institutions. Apart from making part of the AMP capacity of disinfecting facility available for mould removal and drying of documents, we also provided space in our vacant depositories for storing parts of those archives and records offices the premises of which could not be used for a long period of time due to floods. Our archives conservators helped to recover such valuable old documents as the commemorative book from the archives of the Czechoslovak Hussite Church.

The experience gained by the archives during flood aftermath recovery helps us make some general conclusions :

• It is necessary to build archives outside flood areas. This requirement seems quite natural now, but in the first half of 1990s when the new building for our archives in Prague-Chodovec was designed we were constantly reassured that thanks to the system of Vltava dams there is no danger of mass flooding of Prague.
• Documents must be deep-frozen in the shortest period of time, i.e. not longer than several days to avoid spread of mould growth. This is crucial in case when the outside temperature is more than 20°C. Transport and capacity of refrigeration plant proved minor problems compared to considerable costs for keeping the records deep-frozen.
• There are several effective drying methods, neither of them being the best. It is therefore necessary to combine different methods when drying diverse materials.
• Even if there are no visible traces of mould growth all materials must be disinfected. Appropriate disinfecting process can eliminate mould growth as well as other germs that may present health risks and that the records can be contaminated with.
• It is also important to bear in mind the limited personnel, material and space capacity of some professional archives designed for standard “peace” conditions rather than emergency salvage during natural disasters and in the aftermath recovery that sometimes goes for several years. This applies especially to the disinfecting chambers, conservation centres and depositories designed for temporary storing of documents.
• Co-ordination of activities of individual specialised units is inevitable especially during the selection of recovery methods and procedures, when co-ordinating mutual, inter-disciplinary and international assistance. Some institutions that suffered just minor damage or where documents of less importance were damaged may find it more useful to do recovery works by themselves in case the nationally co-ordinated salvage proves to be slow and less advantageous. This is however determined by sufficient financial and technical resources; they are however the precondition of any recovery action.