STEMSEAS24

Large-scale deforestation of the U.S. East Coast during the 19th century increased runoff, amplifying floods as well as coastal sediment delivery. Much of the landscape has since been reforested but flood risk assessments (e.g., FEMA 100-yr flood maps) are often skewed by large floods from this earlier, high-runoff, regime. Likewise, environmental conditions in downstream ecosystems shaped by flood derived legacy sediment and freshwater inputs may not be sustained in the future. This research cruise will address the need for more accurate forecasting by assessing: (1) the dependence of flood frequency on landcover and (2) how land-use and storms have shaped coastal environments. A comprehensive record of past floods on Chesapeake Bay Rivers and land use will be compiled from historic records and sediment cores. Land-use changes will be reconstructed from analyses of downcore pollen assemblages. Grain-size variability and changes in the oxygen isotope fractionation of benthic foraminifera will be used as proxies for past flooding and salinity change, respectively. Incorporation of these data into flood frequency analyses using USGS Bulletin 17C guidelines will be used to improve risk forecasts for partners tasked with flood mitigation such as FEMA, the Army Corps of Engineers, the National Park Service and local governments.