Erosion Rates and Land-use History in Southern Michigan

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Abstract
The quantities and kinds of sediment that have accumulated in Frains and Murray Lakes, Michigan, over known intervals of time, provide a measure of erosion from the watersheds. This study has focused on the ash-weight of sediment and has derived estimates of ‘sediment yield’ from the landscape, though estimates of sediment yield from watersheds have seldom been made from the quantity of sediment accumulating in natural lakes. An exception is Mirror Lake, New Hampshire, where estimates from a core could be compared directly with sediment yields monitored in the last few years in experimental watersheds in the surrounding Hubbard Brook Forest (Likens & Davis, 1975). Detailed study of sediment cores can yield much more information than has been presented here. The chemical constituents of the sediments yield information about the chemistry of lake water and runoff from the watershed, while the remains of phytoplankton that are preserved in the sediment show the progress of eutrophication. A recent study of pre- and post-settlement sediment at Linsley Pond, Connecticut, is an example of a multidisciplinary approach to the determination of human influences on lake history (Brugam, 1975).The data from Frains Lake permit a reconstruction of erosional events since Man arrived on the scene. The result is similar to Wolman's (1967) history of erosion in the vicinity of Baltimore, Maryland; his reconstruction, however, was based entirely on analogy with modern watersheds that were experiencing different kinds of land-use at the current time. Thus his estimate of pre-settlement erosion, for example, is tentative because there are no undisturbed watersheds today to measure for comparison.