Slackwater deposits as paleostage indicators in Canyon reaches of the Central Appalachians: Reevaluation after the 1996 Cheat River flood

A 100-year flood on the Cheat River in January 1996 left sandy deposits less than 0.5 in below high-water marks indicated by flotsam and erosional trim lines. This relatively close match suggests slackwater deposits in Appalachian canyons have good potential as paleostage indicators that may allow regional flood records to be extended back several centuries. The accuracy of the stage record varies with landscape position; deposits in caves and on sheltered terrace surfaces are closer to high-water marks than deposits at tributary mouths, floodplain obstructions, or recesses along channel margins. The good match between slack-water deposits and high-water marks from the 3350 m(3)/s 1996 flood contrasts markedly with the poor match found after an extraordinary (>500 year) 5380 m(3)/s flood in November 1985. The 1985 flood stage was so much higher than floodplain and terrace surfaces that it lapped upon steep colluvial slopes, well above minor fluvial landforms favorable to deposition. Accordingly, depositional evidence of moderate paleofloods in Appalachian canyons may have greater preservation potential than evidence of extreme floods. All slackwater deposits in humid climates are vulnerable to post-flood modification, including those formed in caves. Those in canyon reaches are particularly vulnerable in the face of the construction and maintenance of transportation corridors. Reconstruction of long-term Appalachian flood chronologies based on slackwater deposits will require careful planning, detailed air-photo interpretation, and substantial fieldwork, including more studies documenting the relationships between high-water marks and stage indicators left by other floods on other rivers in the region.