Scour Development and Possible Effects of Momentary Liquefaction in Inundated Coastal Areas During Hurricane Michael

Scour holes around slender piles were measured in areas inundated during Hurricane Michael and were compared with scour hole depths estimated from existing scour prediction equations. Despite testing a wide range of feasible input parameters, some measured scour depths could not be predicted by five common scour prediction equations (one wave only, three current only, one wave and current equation). Current only equations yielded the best prediction rate despite the site being in a wave-dominated environment. The scour depths that were not accurately predicted by the equations tended to be underpredictions despite the range of input values. A range of factors were considered that might have caused these differences. Momentary liquefaction was investigated as one possible explanation to some of the discrepancies between observed and predicted scour depths using laboratory tests and field measurements. The results suggested that momentary liquefaction of the top layer of sediment is possible for wave heights of approximately 0.83 m in 1.3 m of water depth, indicating that momentary liquefaction of sediments was possible during Hurricane Michael with 2 m waves in 3.5 m of water and therefore presents one possible explanation for the observed mismatch between the scour predictions and observations.