| Coastal Plain forested wetlands in the Mid-Atlantic United States provide the final locations for sediment storage before it reaches sensitive estuarine and marine environments. Sedimentation rates, suspended sediment concentrations, hydroperiod, substrate characteristics, surface micro-topography, and vegetation were measured in field studies in eight 1-ha floodplain sites along three tributaries of the Chesapeake Bay to determine the main controls on suspended sediment transport, substrate patterns, and deposition rates and patterns in Coastal Plain floodplains. Suspended sediment concentrations were high throughout the floodplains during overbank flow events and during low and moderate events within favored flow paths. Net long-term mean deposition rates are always lower than means determined from annual clay pad measurements. Local topography (sloughs and low-lying flow paths) and antecedent inundation conditions have strong influences on sediment concentrations and short-term (annual) deposition rates and patterns. Long-term net deposition patterns are largely controlled by distance from the channel. Multiple regression and spatial pattern analyses suggest that net deposition rates and substrate properties are controlled by the frequency and duration of inundation events, the total annual inundation, the manner that sediment is distributed through the floodplain (dominant flow paths and/or the presence of slough networks, for example), and the potential for deposition of suspended sediments. Altered hydroperiod, sediment yields, and/or loss of connectivity between the channel and floodplain by land use changes within the studied floodplains have changed the fluvial geomorphic processes, affecting floodplain sediment storage. These findings suggest that understanding the fluvial geomorphic processes that control deposition rates and patterns with respect to dominant watershed land use patterns is critical for effective water quality management and the protection and restoration of vegetation diversity within the Coastal Plain.*; *This dissertation is multimedia (contains text and other applications not available in printed format). The CD requires the following system requirement: Microsoft Office. |
