INNOVATION July-August 2013

f ea t u r e s

Germany And Alberta’s Floods – Flood Risk Reduction Lessons for BC?

Dr. Matthias Jakob, P.Geo. Kris Holm, P.Geo.

In June 2013 Germany experienced another “century flood,” or “Jahrhunderthochwasser.” The last one had occurred in 2002 and, once again, towns and cities were under water. Only weeks later, a century flood took place in Alberta. Major flooding had previously taken place in 2005, and here too towns and cities were again submerged. Germany is an industrialized nation and has spent hundreds of millions of euros on risk-based flood assessment and control since the 2002 flood. So how, only 11 years and some 20 billion euros in costs after the last flood catastrophe, could a flood result in another 11 billion euro bill? Canada, too, is an industrialized nation, and no stranger to flood disasters over the past two centuries. In light of these recent flood disasters in Europe and Alberta, we wish to prompt discussion on how we can reduce the risk of similar disasters in British Columbia. Germany’s Flood Spring of 2013 was one of the wettest ever measured in some areas of Central Europe, and for five days in a row, two low-pressure systems produced incessant rain that fell on already wet ground. The low pressure system, “Frederik,” formed over Central Europe during late May and funneled wet air masses counterclockwise into Central Europe via the Black Sea and central Eastern Europe. The other low pressure system, “Günther,” was centred in the Carpathians and enhanced Frederik by continuing the rotational airflow towards the Alps. Two stable high-pressure systems over the east Atlantic and Western Europe assured the persistence of the low-pressure systems. By the time the air masses reached Germany, they had cooled and entered from the northeast. Reaching mountain ranges in the German middle mountains and finally the Alps, orographically enhanced uplift resulted in huge precipitation amounts in excess of 400 mm. In Bavaria, Saxony, Thuringia and Hessen a total of 13.4 billion cubic metres of water fell within four days. The return periods on many rivers well exceeded 100 years as well as previous records set in 2002 and 2005. New records were reached on the Danube at Passau, exceeding the record previously set in 1501. River stages on the Saale, Zeitz on the Weisse Elster were the highest measured in the last 400 years. Had it not been for very low snowlines (down to 1,000 m in parts of the northern

Gera, Germany, near the Weisse Elster River in June 2013 following the peak of the flood. Taken on Oststrasse.

©iStockphoto.com/Kerstin Waurick

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