This study examined the stream chemistry changes in Staunton River (a second-order headwater stream with an average annual discharge 704 m3 ha-1 yr-1, Shenandoah National Park, Virginia) resulting from a catastrophic flood in June 1995. This flood, which followed after 800 mm of rain in a 4-day period, caused large-scale debris flows and complete scouring of riparian soils down to bedrock in the lower 2 km of the stream, and has been estimated to be a 1000-year flood. The flood affected stream chemistry on both short- and long-term time scales. The primary short-term response was elevations in stream concentration of Ca2+, Mg2+, and K+ by 59%, 87%, and 49%, respectively, for 6 months immediately following the flood. The long-term impact of decreased concentration of all base cations and SiO2 during summer months (8% average) lasted about 2 years. At the episodic time scale, Ca2+, Mg2+, and K+ flushed from soil sources during pre-flood storms while Na+ and SiO2 diluted; these trends generally reversed during post-flood storms for 2 years. Short-term effects are attributed to the leaching of unconsolidated soil and upturned organic matter that clogged the streambed after the flood. The long-term and superimposed episodic impacts may have resulted from the loss of riparian soils and vegetation in the flood.
All Science Journal Classification (ASJC) codes
- Water Science and Technology