THE FIRST WORD

scouring
Federal investigators plan to announce soon that flood-caused erosion along the riverbed—known as scouring—exposed an Exxon Mobil Corp. pipeline on the Yellowstone River in Montana in 2011... 

Types of scour can include bridge scour, where sediment is removed by the current, leaving "scour holes" and weakening the bridge; strudel scour, where spring-melt runoff from sea ice at shallow depths leads to turbulence that creates depressions in the sea floor; and tidal scour, the erosion caused by the tides, especially in bays.