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Riparian zone functions: sediment and contaminant trapping and vegetation along the Pocomoke River, Maryland.
HUPP, CLIFF1, ALEXANDER, LAUREN1, 2, YANOSKY, THOMAS1, 1 2
ABSTRACT- Extensive channelization along upstream parts of the mainstem and along most tributaries of the Pocomoke River, Delmarva Peninsula, has decreased rates of sediment deposition within the riparian zones and degraded water quality near the river mouth on the Chesapeake Bay, where repeated fish kills have been reported. Our central purpose is the estimation of the effectiveness of sediment- and contaminant-trapping functions in riparian areas along this Coastal Plain river. Short- and long-term sedimentation rates were estimated along several reaches using artificial marker horizons and dendrogeomorphic techniques, respectively. Additionally, sediment chemistry (phosphorus concentration), coincident tree-ring chemistry, and vegetation analyses have been conducted at most of our sites. The mean weight of mineral deposition was least in the headwaters (0.06 g/m2) slightly greater along channelized reaches (0.43 g/m2), and greatest (4.7 g/m2) along unchannelized reaches in the lower basin where riparian areas are in intimate contact with high flows and may be exposed to prolonged flooding. Decreased sedimentation along channelized reaches suggests that channelization has compromised the natural and former ability of the river to maintain water quality. Additionally, woody species diversity and surface heterogeneity is low along channelized reaches and both are relatively high along the unchannelized reaches. Concentrations of phosphorus in sediments and in the wood of trees likewise are proportional to rates of sedimentation along the axis of flow.
KEY WORDS: riparian zone, sedimentation, channelization disturbance, contaminant trapping