Improved flood risk assessment : new data sources and methods for flood risk modelling Rivers have always flooded their floodplains. Over 2.5 billion people worldwide have been affected by flooding in recent decades. The economic damage is also considerable averaging 100 billion US dollars per year. There is no doubt that damage and other negative effects of floods can be avoided. However this has a price: financially and politically. Costs and benefits can be estimated through risk assessments. Questions about the location and frequency of floods about the objects that could be affected and their vulnerability are of importance for flood risk managers insurance companies and politicians. Thus both variables and factors from the fields of hydrology and sociol economics play a role with multi layered connections. One example are dikes along a river which on the one hand contain floods but on the other hand by narrowing the natural floodplains accelerate the flood discharge and increase the danger of flooding for the residents downstream. Such larger connections must be included in the assessment of flood risk. ...