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Harvard Forest REU Symposium Abstract 2019

• Title: Quantifying flood magnitude from particle size characteristics of flood deposits in Amherst Lake, Vermont
• Author: Tania Figueroa Colón (University of Puerto Rico - Mayaguez)
• Abstract:

  Clastic sediment layers in lakes are often the result of erosion in watersheds upstream and transport by rivers. This project focuses on the clastic sediment that is deposited in Amherst Lake, Vermont, and is aimed at determining the grain size of the clastic sediment, how it varies through the lake, and whether such deposition is related to flood magnitude and frequency. Sediment cores and samples collected in June from the river delta and across the lake were analyzed using particle size analysis, loss on ignition, and x-ray scan. By conducting GIS-based analysis, the area of active landslides in the watershed has been identified from historical aerial photographs from 1942, 2011, and 2016, indicating an increase from 5,978.12 m2 to 23,846.93 m2. Estimates of flood discharges were derived for flood deposits associated with Tropical Storm Irene in August 2011, and events on June 30, 1973 and April 15, 2019. Additional sediment observed in cores collected in 2019 and not present in cores from 2013 reveals continued deposition of clastic sediment related to the 2011 Tropical Storm Irene flood. The difference in max particle size (ie D90) between proximal and distal cores appears to provide a reasonable estimate of flood magnitude for the most extreme floods, 271.6263 m3/sec for Tropical Storm Irene, and 217.8799 m3/sec for 1973 flood. However, it appears to overestimate discharges associated with moderate floods since it estimated a discharge of 127.5242 m3/sec for April 2019 flood.

• Research Category: Watershed Ecology; Historical and Retrospective Studies; Group Projects