TREE-RING RECORDS OF LARGE-SCALE FLOODING ON THE LOWER MISSISSIPPI RIVER

An important drawback to understanding the frequency and magnitude of significant flooding on the Lower Mississippi River (LMR) is the relatively short instrumental record of flooding. Bottomland hardwood trees growing in the riparian zone can record major flood events as inter-and intra-annual variability in size, shape and arrangement of vessels in the annual xylem growth increment. We have recently made collections of several tree species (e.g., Quercus lyrata, Q. macrocarpa) at three sites in the LMR. At each of these sites sampled trees exhibit notably anomalous anatomy of growth increments formed in years coinciding with major floods during the instrumental period. We have used these “flood rings” to develop chronologies of past flood events in the basin for the past several hundred years. We compare our chronologies with instrumental and historical records of flooding and find that the tree-ring record includes nearly every major flood in the modern period and significant floods documented in the 18th and 19th Centuries.