RECONSTRUCTING PALEOFLOODS IN THE BEDROCK GREENBRIER RIVER USING SLACKWATER DEPOSITS AND HYDRAULIC MODELING

Slackwater deposits and hydraulic modeling will be used to extend the historical record of flood events and determine the critical threshold of erosion in the Greenbrier River of southeastern West Virginia (SE WV). The southward flowing bedrock river incises Paleozoic sandstones, limestones, and shales. The Greenbrier River has experienced three catastrophic floods in the last 33 years: the 1985, 1996, and 2016 floods. The events caused extensive damages in communities alongside the river; the most recent flood destroyed roughly 1,200 homes in the Greenbrier River watershed. This study will better constrain the frequency of floods that have the potential to cause similar damage, which is a matter of urgent need. Also, changes in historic flood frequencies in relation to climate change can be better predicted by studying paleostage indicators (PSIs) from past climate regimes. PSIs can be used as proxies for extending the historical record and reconstructing recurrence intervals of floods. The PSIs are found in nearby caves, but may also include tree scars and surface deposits. Radiocarbon dating will be used to determine ages of pre-historic slackwater deposits (floods) in the caves. Known discharges and recoverable paleostages will be used to calibrate channel roughness in a 1-dimensional modeling program, HEC-RAS. The 100-year flood frequency will be re-evaluated using the back-calculated paleodischarges recovered from modeling pre-historic floods.