South Carolina floods could be 1,500 year intensity

In some places JBA Risk Management estimates the South Carolina floods to have an intensity of 1-in-1,500 years


PRESS RELEASE: 09 October 2015


World leading flood experts, JBA Risk Management, estimate that in some places the South Carolina floods are approaching a 1-in-1,500 year intensity.

JBA Risk Management has just released new flood maps for the USA. Having compared some of the inundated locations in South Carolina with these maps, it seems that the event has reached an estimated 1-in-1500-year intensity at some locations. 

Iain Willis, Technical Director at JBA Risk Management said, “Based on the observed rainfall from the Carolinas flooding and our US rainfall models, the floods in some parts of South Carolina have reached at least a 1-in-1000-year intensity.  It is even looking likely that a few places could have experienced an extreme 1-in-1500 year intensity.”  Not everywhere has experienced flooding of such severity, however. 

Mr Willis goes on to explain, “It should always be recognised that while some places might have experienced an extreme intensity, say a 1,000 or 1,500 year level, other places not far away might have only experienced a 200-year level, or perhaps even lower.

This is one of the factors that make the assessment of flood risk so tricky for insurers but a footprint of the event can be very helpful in this regard.  An event might cause a 1-in-200-year flood to location A and a 1-in-1000-year flood in a nearby location B, due to difference in topography, and drainage, etc.  One of the benefits of having flood maps for multiple return periods is that each location can be matched to the corresponding map and “cut out”. Then the different cut outs can be stitched together to create a footprint of the whole outline.  There are other ways of creating flood footprints using hydraulic modelling, and so on for all locations in the flooded area."

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