Assessing the impact of weir construction on recent sedimentation using cesium-137
Ten cores were obtained from a marsh developed along Mad Island Slough, Texas, USA, upstream of a weir constructed in 1948. The cores were analyzed for cesium-137 to identify time-stratigraphic marker horizons and calculate recent sedimentation rates. The cesium-137 analysis provided a 1954 marker horizon in nine of the ten cores. A second marker horizon, present in all ten cores, consisted of an abrupt downcore change in lithology from dark organic-rich muds to grey organic-poor sands. This transition was tentatively identified as coinciding with 1948 and the beginning of marsh sedimentation. Resulting sedimentation rates show that surprisingly little sedimentation has occurred behind the weir, averaging only 27 cm in almost 50 years. Sedimentation rates in the marsh declined from an average of 2.4 cm yr−1 in 1948–1954 to 0.32 cm yr−1 in 1954–1994. A similar trend of declining sedimentation has been documented for adjoining Mad Island Lake, suggesting that land-use changes in the lake's watershed have reduced the sediment supply in recent decades. The results also suggest that the weir is not a very efficient sediment trap in this watershed.
Key wordsCesium-137 Sedimentation Wetlands Land-use change Weir
Unable to display preview. Download preview PDF.
- DeLaune RD, Patrick WH, and Buresh RJ (1978) Sedimentation rates determined by137Cs dating in a rapidly accreting salt marsh. Nature 275:532–533Google Scholar
- Gustafson PF (1969)137Cs in the US diet 1961–69 and the influence of climatic and agricultural factors. Proceedings of the Symposium on Environmental Contamination by Radioactive Materials, United Nations. Vienna, pp. 135–143Google Scholar
- Oenema O and DeLaune RD (1988) Accretion rates in salt marshes in the Eastern Scheldt, South-west Netherlands. Eustarine, Coastal Shelf Sci 26:379–394Google Scholar
- Pennington W, Cambray RS, and Fisher EM (1973) Observations on lake sediments using fallout137Cs as a tracer. Nature 242:324–326Google Scholar
- Rember WC, Erdman TW, Hoffmann ML, Chamberlain VE, and Sprenke KF (1993) Dating of mine waste in lacustrine sediments using cesium-137. Environ Geol 22:242–245Google Scholar
- Williams HFL (1994) Paleoecological evidence of salinity changes in Mad Island Lake, Texas: Application to determining recent lake sedimentation. The Nature Conservancy of Texas Research Report. 41 ppGoogle Scholar
- Williams HFL (1995) Foraminiferal record of recent environmental change: Mad Island Lake, Texas. J Foraminiferal Res (in press)Google Scholar
- Williams HFL and Hamilton TS (1995) Sedimentary dynamics of an eroding tidal marsh derived from stratigraphic records of cesium-137: Fraser Delta, British Columbia. J Coastal Res (in press)Google Scholar