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Harvard Forest Symposium Abstract 2010

  • Title: DIRTY WATER: A PAIRED WATERSHED STUDY OF SUSPENDED SEDIMENT CONCENTRATIONS IN WORCESTER AND HARVARD FOREST
  • Primary Author: Renee Harkins (College of the Holy Cross)
  • Additional Authors: Sara Mitchell (College of the Holy Cross)
  • Abstract:

    By assessing stream hydrology, geomorphology, and land use, I investigated how urbanization impacts suspended sediment concentrations (SSC) in two similar streams. My study area included one urban watershed (Beaver Brook, Worcester) and one forested watershed (Bigelow Brook, Harvard Forest). I predicted that the urban watershed would have higher SSC values during comparable rainfall events than the forested watershed due to anthropogenic effects. Throughout the study period (June 2009 February 2010) I used a US DH-48 integrated depth sampler to collect water samples from which SSC was calculated. In the Beaver Brook watershed a rainfall event of ~14 mm caused stream discharge to rise from 0.032 cms to 0.101 cms and the SSC to rise from low flow concentrations of ~3 mg/L (D = 0.040 cms) to 9.78 mg/L. In the Bigelow Brook watershed the same rainfall caused stream discharge to rise from 0.0010 to 0.0025 cms with no increase in SSC. Land use analysis concluded that 36.6% and 16.0% of the Beaver Brook watershed consists of impervious surfaces and forest respectively, compared to less than 2% and 78.8% in the Bigelow Brook watershed. Impervious area facilitates rapid hydrologic fluctuations in streams due to increased runoff, thereby increasing overland erosion and channel scour. Therefore, the higher SSC values observed in the Beaver Brook watershed are believed to result from enhanced erosional processes due to impervious cover in the watershed. Future work includes measuring the organic carbon content of suspended sediment.

  • Research Category: Watershed Ecology