Flood Resilience - At first sight, climate change and plant safety seem to be separate issues, with the first one having much more public attention. However, we did not need Fukushima to demonstrate that natural hazards can be a major risk for any technical installation.

A guideline is being developed by the German Commission on Process Safety to increase the resilience of chemical plants against floods, taking into account the expected climate change.

Water - Resource and Risk for Chemical Plants

Climate change is one of the hottest topics both in the scientific as in the media world. Although its root causes and final consequences are still under heavy debate, an increase of extreme weather phenomena cannot longer be denied. This is not limited to but includes heavier precipitation. On the other hand, water is one of the most important utilities for chemical plants.

Easy access to sufficient cooling water was one of the main reasons for building many chemical plants near rivers. Those plants had always to manage the risk of floods (as well as of droughts). A risk of flooding also exists in coastal areas and even at locations far away of surface water as a possible consequence of heavy local rain.

Flooding of chemical sites causes a number of severe risks. Hazardous chemicals from storage areas can be washed into the floods leading to environmental damages. Process equipment can be damaged by floating up or struck by swimming debris, also leading to hazardous emissions. In addition to the risks for people and environment the damages caused by flooding itself and the following business interruption can have a dramatic economic impact.

Regulation Of ‘Natech' Risks

Those risks are well known to the operators as well as to the regulators. One of the basic requirements of the German statutory order on hazardous incidents - by which the European Seveso Directive for major hazard installations has been implemented - is protection from natural hazards. This includes not only flooding, but also snow, wind, earthquakes, etc. In the upcoming revision of the Seveso Directive, those "natech" risks (the combination of natural and technical risks) will be emphasized stronger, too.

The risk of floods is well known. Authorities and insurers have invested a lot in mapping risk areas. Most chemical plants in those areas have taken this risk into account both by technical measures as in their emergency plans. Therefore the consequences of floods to chemical plants have been limited in the past.
However, a number of questions remain open, especially:

• On which severity of floods (esp. water level) the safety measures have to be based?
• How to assess the risk of flooding by heavy rainfall?
• Are the existing data on floods and rainfall still valid under the assumption of a climate change?

New German Guideline (TRAS)

These were the questions that prompted the German Commission on Process Safety (which advises the federal government) to work out a technical guideline (TRAS) for the protection against floods and heavy rain. It aims especially at major hazard sites covered by the statutory order on hazardous incidents. The project was strongly supported by the German Federal Ministry for the Environment, as it fits into the "German Strategy for the Adaption to Climate Change." Based on two research projects sponsored by the German Federal Environment Agency, the guideline gives recommendations how to assess the risk of flooding in the safety reports and which safety measures could be applied.

For existing installations, floods should be considered that (retrospectively) occur every 100 years. This is the frequency on which the risk maps of the water management authorities are based, too. Flooding by local heavy rainfall recommendations for a case-by-case assessment are given, also based on retrospective data. In general, the balance has to be made up between inflow and outflow of water from different sources.

The ‘Climate Factor'

As this is more or less a traditional approach, the provisions for climate change needed an intense discussion. It would be neither reasonable nor legally acceptable for operators of chemical plants or for their competent authorities to follow up and evaluate the highly controversial scientific discussion on climate change. The commission therefore opted for a pragmatic approach. It recommends adjusting the (undisputed) retrospective data for water levels and rainfall by a "Climate Factor" of 1.2 for new installations with a lifetime until the year 2050. A 20 % increase of the severity of floods and heavy local rainfall until 2050 is well in between most scenarios of the scientific debate on climate change. This Climate Factor need not be applied if more specific knowledge is available, and it will be reassessed every five years.

The German statutory order on hazardous incidents also requires that the operator consider major hazards with a very low probability of occurrence but catastrophic consequences. Due to the low probability, technical safety measures may not be reasonable, but measures to mitigate the consequences may be necessary. The commission decided that for this purpose flooding of the site should be assumed, regardless of any cause, if the risk of flooding cannot be excluded a priori.

The draft of the guideline (TRAS) has been successfully tested for its practicability and was during the last months open to comments from all interested parties and especially the competent authorities of the German federal states. The Commission on Plant Safety will decide upon those comments in the coming weeks. The draft (and later the approved guideline) is available at www.kas-bmu.de.

Other ‘Natech' Risks

Floods and heavy local rain are not the only natech risks to be considered. For other risks caused by heavy precipitation (snow, hale, landslides etc.), the commission regarded the information as not yet sufficient for a guideline. However, these risks are covered in supplementary information to the TRAS, which is published on the same website. For strong winds, another guideline is under consideration by the commission. For earthquakes the German Chemical Industry Association has recently issued a guidance. Lightning is covered since long by safety regulations. It remains a duty of any operator to assess all possible hazards for chemical plants. Guidelines as the above mentioned cannot repeal this duty, but help in fulfilling it.