UCLA’s Daniel Swain co-authored a new study published in Communications Earth & Environment which addresses questions related to why climate-related increases in extreme precipitation have not been reflected in an increase in annual floods. 

Researchers found that severe flooding, occurring every 10 or 20 years, likely will not change for the remainder of the century. However, catastrophic floods will likely increase, potentially leading to $1 trillion in damage and forced evacuations for millions of people. These events, historically only occurring every 50 to 200 years, have seen a 300% to 400% increase in probability. Swain explains that the reason for the difference is logical. Warming due to climate change can cause land to dry out and drier land is able to absorb more water — this can mitigate some routine flooding. Even so, there are thresholds and limits to what can be prevented. Soil will eventually saturate and the water can then overwhelm a watershed. 

The study used computer modeling to create multiple plausible versions of climate outcomes, assuming that there would be no serious effort to cut greenhouse gas emissions. Modeling increased the amount of data available for study by 50 times what was available from history alone. In addition, estimates of Bavaria’s hydrological system were also generated — the hydrological system is a term describing a range of natural processes including the ground’s capacity to absorb moisture. Bavaria was chosen as the model because it has good data, but the findings are likely applicable to most of the world.  

Learn more at UCLA Newsroom.