What are the causes, patterns and effects of disastrous river flood? An international group of researchers led by GFZ hydrologist Bruno Merz has investigated this question in a review article published in the journal Nature Reviews Earth and Environment. The short answer: It's complicated. What is certain, however, is that there is an opposing trend of property damage and personal injury. Since the 1990s, the number of fatalities from river floods has declined worldwide, but the amount of damage has risen sharply. The researchers attribute the decline in casualties to improved flood warning, technical protection measures and heightened hazard awareness.