HR: 0830h
AN: H51E-1127    [PDF]
TI: Using Fallout Radionuclides and High-Resolution Survey Data to Study the Erosion of Recently Exposed Lake Deposits in New Hampshire
AU: * Kaste, J M
EM: jim.kaste@dartmouth.edu
AF: Department of Earth Sciences Dartmouth College, HB 6105 Fairchild, Hanover, NH 03755 United States
AU: Heimsath, A M
EM: arjun.heimsath@dartmouth.edu
AF: Department of Earth Sciences Dartmouth College, HB 6105 Fairchild, Hanover, NH 03755 United States
AU: Hamlin, A T
EM: Alexander.T.Hamlin.03@Alum.Dartmouth.ORG
AF: Department of Earth Sciences Dartmouth College, HB 6105 Fairchild, Hanover, NH 03755 United States
AB: Establishing rates of sediment transport processes can be difficult, but a detailed understanding of how rapidly landscapes erode is a critical component of quantitative geomorphology and effective resource management. Here we use high resolution survey data and fallout radionuclides to study hillslope erosion in New Hampshire, U.S.A. The hillslopes in this field site are composed of silt and clay deposited by Lake Hitchcock at the end of the Wisconsinin Glaciation, and represent approximately 12,500 years of erosional processes. The landscape is covered by mature White Pine stands, and active bioturbation by woodchucks, earthworms, and tree throw is observed. We use survey data to calculate slope and curvature at high resolution (1 to 2 m) across the hillslope profile. Assuming that sediment flux is linearly dependent on slope, we calculate an erosion rate of 48 m/ma on divergent hillslopes. Other field evidence suggests that at least 12 m of lake sediment has been eroded from the hillslopes since the lake drained, yielding an erosion rate of approximately 1000 m/ma. This implies a significant change of erosion rates in the short time that the landscape has evolved, or, that the linear assumption is not valid. We also use fallout 210Pb and 137Cs inventories to provide further clues to sediment transport processes on decadal timescales, and compare it to the survey data which represents millennial timescale processes. Erosion and sediment redistribution on these hillslopes is relatively rapid, largely due to the easily-erodable parent material.
DE: 0400 Biogeosciences
DE: 1600 GLOBAL CHANGE (New category)
DE: 1625 Geomorphology and weathering (1824, 1886)
DE: 1815 Erosion and sedimentation
SC: Hydrology [H]
MN: 2003 Fall Meeting