Abstract: Problems with extreme floods have been aggravated in Germany mainly due to loss of flood retaining areas caused by river regulation measures in former centuries, and by intensified use of the former natural flood plains. The situation may have been worsened in the last decades by climate change. The recent August 2002 economic flood damage in the Elbe river basin added up to 9.2×109 (100×109 ￥). Numerous levee breaches happened. Also other German bigger rivers like the Danube and the Rhine river caused considerable damage to buildings and infrastructure in the previous decades, and many lives have been lost. The contribution centers flood detention measures in the Elbe valley in Eastern Germany and in the Upper Rhine valley in Southwest Germany, adjoining to France. Detention basins in the Upper Rhine region are mostly located along the levees or alongside a reach upstream a river barrage. They can be operated in principle either with or without movable control devices. The Integrated Rhine Program (IRP) of the Federal State of Baden-Wuerttemberg aims as well at flood protection for the riparian users and the downstream riparian residents up to a 200 years flood, as at floodplain forest revitalization behind the dikes. Flood risk mapping by use of GIS and simulation of flooding processes in the valley of the Neckar river, an affluent to the River Rhine, will be presented. It is part of the Integrating Conception for the Neckar river basin, called IKONE. Damages to buildings have been estimated for different floods with certain annual probabilities of exceedance. Apart from flood protection by means of dikes and flood detention basins, also flood safety has to be paid attention. Flood safety means preventing excessive damage due to the exceedance of the design flood event, e.g. the 200 years flood. Dangerous surges can occur following dike breaches, caused by uncontrolled levee overflow. The term 'residual risk' is rather belittling. Constructing spillways as countermeasure against uncontrolled overflow of dams and barrages is common practice. This is obligatory in the design of even small flood detention basins, for river barrages and their upstream reach, and certainly for large dams and multipurpose reservoirs. It will be pointed out, that this design case has to be taken into account likewise in case of diked river stretches. Depending on the circumstances onsite, overflow sections or movable gates can serve as emergency outlets to prevent huge losses.

Key words: flood risk management, large river system, Germany