Flooding - There is no such thing as complete protection

Not again. Just ten years after the "hundred-year flood" of August 2002, vast areas of Germany were once more left submerged under water in June 2013. What are the factors involved in such severe weather events? What can the state, individuals and the insurance industry do to tackle such large-scale flooding and keep damage and losses to a minimum?


Moist, warm Mediterranean air is drawn in an easterly direction around the Alps and meets up with cold air from the north and west above central Europe. This produces large amounts of heavy rain, which is intensified by orographic lifting on the north side of the Alps and the eastern low mountain ranges in central Europe. Such weather conditions have occurred with alarming frequency in the last 20 years or so and were the cause of yet another devastating flood catastrophe in southern and eastern Germany in June 2013.

The increased settlement near rivers, combined with a significant rise in the concentration of values in these areas and a growing sense of complacency, have led to soaring loss amounts in recent years. If this trend is to be tackled, more than just individual aspects must be considered. What is needed is a prevention strategy that embraces all aspects of floods, from their formation to the avoidance of loss potential.

Unchecked construction in exposed areas has increased loss potentials

The increase in flood losses is to a large extent due to the growing development of land close to rivers and lakes, where profit and self-interest have invariably taken precedence over common sense. Mistakes have been – and still are – regularly made during construction and land-use planning. This applies not only to the owners of property; equally to blame are those responsible for land-use policy. Anyone wishing to build should be informed of current risk exposure and the potential uninsurability of the property.

Although the German Flood Control Act of 2005 restricts such activities, it cannot prevent them entirely. In order to avoid unchecked developments in exposed areas, the responsibility for land use clearly needs to be shifted to a regional or national level where decisions that consider all factors and involved parties can be made. The benefits that any one community or resident located beside a river may derive from particular measures should not burden society as a whole.

Engineering measures to prevent flooding

The top priority of any prevention strategy is to hold back flood waters. The most efficient solutions – but also the most difficult to implement – are large flood detention basins and polders. These are located directly alongside the river and are flooded when needed in order to reduce the flood peaks.

However, the construction of polders has met with fierce resistance from many property owners, for example along the Danube in Bavaria where the authorities have been trying to build polders for years. Some measures such as infiltration areas or local retention have only a limited impact. Still, they need to be built. Reducing the height of flood waves by just a few centimetres can prevent a dyke from overflowing.

Dykes can burst

Dykes are constructed on the basis of a design event, which as a rule is derived from a statistical exceedance probability of once in a hundred years. They are usually only breached when the design event has been far surpassed. From this standpoint, such cases are not really failures. Hundred-year floods occur frequently in localised cases. Therefore, if one considers 100 statistically independent watercourses, it is reasonable to expect a flood to occur in one of these locations once a year on average.

However, in 2013 a very large area was hit by the flooding, thus leading to the catastrophe. In the future, more thought should be given to the incorporation of spillways in river dykes – like those built into dams. This would mean that if the discharge capacity were exceeded, areas of lower criticality could be flooded intentionally.

River restoration is not a panacea

While river restoration and relocating dykes farther away from rivers can help, their effectiveness in extreme flood events is limited and usually overestimated. They cannot prevent a highly catastrophic flood nor, in many cases, even reduce its impact significantly. Also, when the retention area is needed – i.e. when the wave crest arrives – it has usually already been depleted by previous overflow.

Prevention measures

The most important factors in minimising losses are optimal preparation for catastrophe situations and professional catastrophe management. This primarily involves early-warning systems and effective alarm strategies – both governmental responsibilities. Risk awareness at all levels is the key to better disaster prevention. The insurance industry plays an important part here by providing clear risk assessments.

Risk-commensurate handling of valuable items

Flood victims themselves can contribute to loss prevention by building appropriately, managing their exposed values, being prepared for emergencies, and being ready to take action in the event of an impending catastrophe. Never before have people had so many valuable, yet also vulnerable, possessions. While coal, wood and other supplies used to be stored in basements, these areas now often contain hobby and party rooms, saunas and oil-powered central heating equipment instead.

The basements of relatively large housing complexes or commercial buildings often contain central control systems for the buildings, storage rooms or even computer centres. Permanent or even temporary structural measures and the appropriate response to flooding danger can help protect these valuables from damage.

Sharing the flood risk

There will always be severe weather catastrophes and there is no such thing as 100% protection. However, that doesn't mean there is nothing we can do to minimise flood losses. Yet simply relying on dykes, early-warning systems or insurance policies is nowhere near enough. Only a combination of measures supported and shared by governments, residents and insurers can effectively reduce flood risks.

Taking suitable precautions increases insurability

Flooding will continue to present a residual risk. And insurers can cover this risk. Nearly 99% of all buildings in Germany can be insured against flooding. Even in Germany's most flood-prone areas, deductibles and prevention measures can make insurance possible. But the need to take preventive measures remains the deciding factor in loss minimisation, even for those already insured.

The insurance industry's primary objective must therefore be to increase motivation in this respect. To achieve this, insurers need to focus on informing the public and heightening the awareness regarding the risks involved. As stated above, there is no way to fully prevent flooding. Even if all preventive measures have been taken, the risk needs to remain firmly on people's agenda. We may have no choice but to live with floods, but suitable risk prevention in combination with appropriate insurance cover can significantly reduce their catastrophic effects.