Compound Flooding

09/10/25

“What happens when two types of flooding happen at once?”

There are multiple styles of flooding. For example, riverine flooding leads to river banks getting inundated, coastal flooding brings ocean tides over previously dry land, and stormwater flooding results in rainwater engulfing surfaces with runoff. Compound Flooding occurs when multiple of these flooding types interact together. Infrastructure planners must account for compound flooding in their work. For example, a sea wall may protect from coastal storm surge, but it can also trap stormwater inside, leading to ponding and all of the issues that come with it.