A Framework for Including Weather and Climate Changes in Flood Risk

There is considerable confusion in the existing hydrological and climate change literature regarding observed and future changes in flood risk related to weather and climate changes.  Part of the confusion arises from an inadequate framework to understand the weather and climate drivers of flood risk. Three different types of floods will be discussed:

·         Riverine

·         Flash Floods, and

·         Tidal and storm surge coastal flooding. 

Large-watershed riverine floods are driven by weather and climate phenomena that operate on multi-season time and large space scales.  These are substantially different than flash floods that are driven by short-term smaller-scale extreme precipitation events. Tidal and coastal storm surge floods operate on various time scales and are driven by changes in sea level and storm climatology.  Analyses of observed changes are used to show how changes in specific weather and climate phenomena contribute to these types of floods, can operate independently, and can be additive to substantially alter flood risk.  Observations and projections of future change indicate that flooding risk attributed to weather and climate has already increased and is likely to continue to increase.