They are developed for areas where a potentially significant flood risk has been identified and show the extent of flooding caused by floods with varying probabilities of occurrence, from more frequent floods (once every 10 years) to extremely rare and extreme floods (once every 1,000 years). They are an invaluable resource for land-use planning, construction decisions, and the design of protective measures.
They provide a more detailed view of the potential adverse effects of floods. They combine information on the probability of flooding with data on the vulnerability of the area, i.e. what buildings, infrastructure, population, or natural assets are located in the flooded area. They have a wide range of uses, from supporting decision-making by local and state authorities, through insurance, to informing residents and planning evacuations in the event of a flood.