INNOVATION July-August 2013

Alps), the floods would have been even more extreme. Prolonged rain on relatively wet ground resulted in up to 50 km long flood surges with very long hydrograph peaks. The rivers Danube, Elbe, Mangfall, Mulde and Elster tripled in width and several dikes failed, inundating 3,350 km 2 of agricultural and pastoral lands. About 60,000 people were evacuated from their homes and over 80,000 emergency personnel were deployed in Germany alone for almost two weeks. In total, the death toll across central Europe was 25, eight of those in Germany. High-powered pumps were employed and road embankments broken up by the German army to allow water to flow back into the rivers where dikes were breached. In Saxony-Anhalt, chemicals were swept into the Elbe River and agricultural and pastoral areas were declared unusable. Groundwater levels reaching the surface mobilized contaminated waters and they became part of the surface water runoff. Many heating oil tanks, typically located in people’s cellars, started to leak as cellars flooded, discharging oil into homes and surrounding surface waters. Hundreds of livestock drowned and in some areas, flood waters rose so fast that many people and businesses were unable to rescue their belongings. These losses were completely uninsured in areas zoned as <10 years flood frequency, or only partially insured in areas zoned as 10-50 year flood frequency. How could this all happen in one of the most technologically advanced countries in the world with a long history of flood risk management?

The case of the town of Grimma, serves as an example in two respects. After the 2002 floods, the local government wanted to construct a concrete wall to protect against future floods; however, construction was delayed by postponements and public intervention until 2007. With only 200 m of the 2,000 m wall constructed, Grimma was flooded again in 2013. On the other hand, many hydrologists in Germany oppose such flood walls because they do not give the river the space it needs to attenuate the flood wave. Forcing the river into a narrow bed may also stress the dikes on the other side and allow rapid propagation of the flood wave into areas downstream. Floods on the Elbe River started in the Czech Republic, where controlled release of reservoirs upstream occurred to manage flooding of Prague from a famous Elbe tributary, the Moldau. While this protected Prague from a flooding catastrophe, it appeared to raise Elbe River flood stages to unprecedented levels downstream. Critics of flood walls, as proposed for Grimma, noted extremely high groundwater levels contributed much of the water that led to the flooding of the historical town. Germany’s Flood Response After the 2002 floods, 530 million euros were invested in flood protection in the state of Saxony, but only 5 million euros were used for the construction of flood retention areas. The lesson, once again, was that construction and sealing of permeable grounds, river straightening, and de-watering of bogs and swamps resulted

June 2013. Calgary’s downtown core saw considerable flooding during Alberta’s most costly natural disaster.

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