In Dortmund the fire brigade faced an unusual flood event in July 2008. A locally restricted but very heavy rainfall exceeded the capacity of the sewer system and caused damage. The response was not appropriate and too slow because of the unusual intensity of the event.
Dortmund, a city of half a million inhabitants, is located in the catchment area of three river-systems. Normally these rivers don’t represent any significant flood risk for the city. Nevertheless a three hour, locally restricted heavy rainfall led to flooding and high damage of property in 2008. The amount of precipitation reached the level of 200 mm, which is more than double the average of July 2008. The reason was a “stationary” thunder storm cell with hail and strong squalls.
The fact that the rain was locally restricted made for a particular challenge. Only few kilometres away in the fire brigade centre there was no unusual rainfall which led to officers misjudging the situation.
After this event a study was commissioned to evaluate the operation and to draw the right conclusions. The study found that the rainfall represented a 100-year event, exceeding by far any other rain since the beginning of intense rain recordings in 1937. It went on to state, that the urban drainage system was completely functional but not designed for such an event. It pointed to the need to take into account the EU Flood Risk Management Plan and to establish a municipal flood control officer.
Implementing the recommendations of the study led to the following activities:
The implementation of the administrative requirements led to a flood checklist for land-use plans and the improvement of the response capacity.
Flood checklist for land-use plans:
Water bodies - Is the area of the land-use plan located within a flood plain of a water body? If so (regardless of the planning permission):
Sewer system - How is the drain of the run-off rain water managed?
An improvement of responsiveness could be achieved by acquiring additional off-road vehicles and pumps.
The fire brigade in Dortmund is ready to respond effectively to the next unusual flood event. It was important to understand the specific and exact shortcomings in order to develop a targeted and effective response.