River Sediment May Hold Key To Land Use Patterns

May 27, 1997

Baltimore, Md. -- A record of rainfall, river flow, land use and human migration may be stacked away in the sediments at river mouths, according to Penn State researchers.

"We are looking at the Susquehanna River Basin and will be looking at sediment cores taken from the Upper Chesapeake Bay to determine the connection between sedimentation patterns at the river's mouth, land use patterns in the basin and climate variability," says Dr. Ana P. Barros, assistant professor of civil engineering.

The researchers have not yet taken sediment cores at the mouth of the Susquehanna -- work begins this summer, but they have pieced together the climate and land use data. They have also tested their hypothesis against an inventory of previous field studies in the estuary.

Barros; Sara J. Gordon, graduate student in geosciences; and Rebecca Bidwell, an undergraduate Women in Engineering and Science Research intern, have combined historic flood and precipitation data with basin geology and changing historical land use patterns to create a database that reflects the effects of people and climate.

The researchers presented their geographic-information-system based basin-scale assessment of land use and climate variability covering 1850 to the present, today (May 27) at the spring meeting of the American Geophysical Union in Baltimore.

Some of the factors considered in the model are farming, human migration, streamflow, rainfall, soil type, economics, land cover and land use. The researchers believe they can determine the sediment that was put down through time by understanding the location of the expected sediment source and the expected amounts of sediment.

"Certainly we should be able to see the major cycles of variability in the climate and erosion regimes in the basin," says Barros. "Such things as prolonged drought or exceptionally wet weather that caused flooding should be evident."

Historic climate data are not continuous or totally accurate. While there is 100 years of good streamflow data and in some places 80 years of rainfall data, in other places there are only 40 or 50 years worth or even less. By looking at the sediment, the researchers hope to link core layers with climate and sedimentary regimes and fill in the missing pieces.

To do this, the core layers will need to be dated. The researchers plan to use lead isotope ratios to determine when the sediment layers were laid down. Pollen included in the sediment can also help with dating.

"This type of dating has been done before by Grace Brush, so we are confident that it can be done," says Barros.

The composition of the sediment layers, including pollen, trace metals and even mine tailings could lead back to the source. If large amounts of sediment can be shown to come from one area of the basin during a specific time period, then that information can be correlated with the rainfall and streamflow data to see if large amounts of sediment were expected from that area at that time.

By linking land use patterns and expected erosion rates, the effects of farming, rail and road construction and other human uses can be assessed and checked in the sediment cores. In this way, the Penn State researchers can attain a better understanding of the interactions between human agency, climate and landscape evolution.


EDITORS: Dr. Barros may be reached at (814) 863-8609 or barros@essc.psu.edu

Penn State

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