Flash floods and Urban flooding
The flooding of July 2021
Severe floods in mid-July 2021 killed at least 220 people in Germany and Belgium. The floods followed 2 days of heavy rain that caused several rivers in the region to burst their banks. The worst-hit areas were around the Ahr and Erft rivers in Germany and the Meuse in Belgium, which experienced the most rainfall in a 24–48-hour period since records began. According to a model study carried out by the ‘World Weather Attribution’ initiative, human-caused climate change had increased the rainfall intensity of such storms by 3–19%, relative to a pre-industrial climate 1.2 °C cooler than today (3). The study concludes that similar events can now be expected to hit any part of Western Europe, in a large region between the north of the Alps and the Netherlands,about once every 400 years. The authors state that the likelihood of such an event to occur today compared to a 1.2 °C cooler climate has increased by a factor between 1.2 and 9.
The draft of the new Federal Water Act provides that in future rainwater must soak away locally, be used for irrigation, or be discharged into a body of water by means of drains kept separate from wastewater sewers. Provisions in bylaws may require the installation of non-return valves for building connections. It may also be necessary to modify sewage systems to prevent flooding (1).
Hamburg has introduced a separate rain water drainage system in recent years and introduced financial penalties, if rain water is not locally drained by home owners (2).
The references below are cited in full in a separate map 'References'. Please click here if you are looking for the full references for Germany.
- Federal Ministry for the Environment, Nature Conservation and Nuclear Safety (2009)
- Schlünzen and Bohnenstengel (2016)
- Kreienkamp et al. (2021)