Flooding can, also in Germany, cause damages amounting to billions. With the flood loss database, HOWAS 21, scientists from the GFZ, Germany's national lab for geosciences have compiled a profound data basis from multiple sources for the research of flood damage. These data serve for a better understanding of the occurrence of flood damage and the assessment of the effectiveness of prevention measures.

The estimation of economic damage is an important component in decision-making in connection with flood prevention measures on the basis of cost-benefit analysis. However, in comparison to other areas of hydrology and water management very little data on flood loss in Germany actually exist. Therefore, scientists from the Helmholtz Centre Potsdam, GFZ - German Research Centre for Geosciences, compiled the database HOWAS 21 on the basis of scientific results within the framework of the program "Risk Management of Extreme Water Events" (RIMAX) which is financed by the German Ministry for Education and Science BMBF.

HOWAS 21 is an object-specific flood loss database for Germany. Damage cases from the sectors private households, business/industry, agriculture, traffic infrastructure, rivers and hydro-engineering infrastructure are filed. To date more than 2700 cases from the private household sector and more than 2000 cases from the business/industry sector are accessible in HOWAS 21.

In addition to the resulting monetary damage e.g. on buildings, household belongings, or business equipment and on surface areas, data on the impact of the event on the object, on the damaged object itself and on damage reduction measures are also registered in HOWAS 21. Each damage case is, furthermore, assigned to a flooding event and a census campaign (Metadata). The attributes in HOWAS 21 are based on criteria, defined through a multi-stage expert survey for each sector.

The technical development of the database took place in cooperation with the Natural Disasters Networking Platform (NaDiNe), an activity of the Helmholtz-Earth Observation Systems EOS. HOWAS 21 is now  online accessible (in German).