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Hydrological accumulation zones (HAZ) are primarily aimed at clients who wish not only to identify individual risks exposed to flood, but also to start adding up their exposures. We have created HAZ worldwide and these can be licensed as a global set or per country. The zones are defined by hydrological catchment areas and are typically available in two tiers within which flood accumulations can be calculated. These tiers are defined by catchment threshold size. The image below compares the county boundaries in St Louis with the 1,000 square kilometre and the 500 square kilometre catchment boundaries. 

Hydrological accumulation zones can also be used for the following:

  • Forming the basis of a flood risk visualisation
  • Defining areas in which a cap should be applied to the amount of business that can be underwritten (again, in relation to a company's risk accumulation tolerance)
  • Defining zones for consistent reporting of exposure data to flood at national or global scales in a consistent and hydrologically sensible manner

Interesting fact: we have mapped 153,483 hydrological accumulation zones across the globe.

For more information about hydrological accumulation zones, get in touch.