Ice storm impacts on woody debris and debris dam formation in northeastern U.S. streams

In January 1998, an ice storm damaged forests in northeastern United States and eastern Canada, causing coarse woody debris (CWD) deposition in riparian areas and associated streams. During 1999 and 2000, tree canopy damage, stream physical habitat, and wood deposition were evaluated within 51 first-, second-, and third-order streams located within five eastern Adirondack Mountain watersheds (New York, U.S.A.). In first- through third-order streams, the number and volume of stream debris dams increased in response to streamside trees with canopy damage. Tree canopy damage was not a significant predictor for individual pieces of stream CWD but was correlated with CWD >10 cm in diameter in third-order, but not first-order, streams. At debris dam locations, bankfull width was greater and stream substrates consisted of increased fines. Woody debris resulting from the 1998 ice storm was not associated with increased pool formation; instead, boulders and rocky substrate were the dominant pool-forming elements. CWD length in first-order streams generally exceeded bankfull width, but in third-order streams, CWD length was shorter than bankfull width and therefore was subject to greater transport and accumulation into debris dams. Our results indicate that ice storm disturbances can increase wood inputs to first- through third-order forested stream ecosystems.