CAS Research Clarifies Role Of ‘Spatial Dependence’ In Flood Risk

It may seem like a no-brainer to say geographies that are near each other share certain risks -- particularly when talking about flood risk, which doesn’t respect artificial boundaries like ZIP Codes. But the ability to quantify such intuitive relationships is critically important to understanding and addressing such perils.

Recent research by the Casualty Actuarial Society (CAS) advances this effort. In a study titled ‘Climate, Spatial Dependence and Flood Risk: A U.S. Case Study,’ CAS researchers have created spatial dependence models for 292 U.S. watersheds spanning the period 1979-2018, with a particular focus on economic flood loss.

‘Spatial dependence’ refers to the ‘the propensity for nearby locations to influence each other and to possess similar attributes.’

The question the researchers were trying to answer was not whether this propensity exists, but, rather, its significance to rising flood-related losses relative to other factors, such as population trends.

Floods caused an estimated $76 billion in global damages in 2020 and constitute nearly two-thirds of all presidential declared disasters in the United States. It is anticipated that by 2050, national scale high tide flooding will occur an average of 45-70 days per year.