Sediment loads and accumulation in a small riparian wetland system in northern Missouri

Sediment transport and deposition along a stream in an agricultural basin (65 km²) in northern Missouri, USA were quantified as part of a long-term study to evaluate effects of silvicultural practices on the hydrology, sediment, vegetation, and wildlife characteristics of remaining forested riparian systems. Median cumulative sediment deposition, measured using feldspar clay pads, increased from August 1995 to August 1998 at a rate of about 1 cm/yr. Median deposition amounts from single floods ranged from 0.03 cm to 0.64 cm. Floodplain and riparian maintenance flows corresponded to monitored floods with calculated recurrence intervals as low as <2 years. Simple linear regression models, using flood event suspendedsediment load or streamflow characteristics, explained up to 82 percent of variability in median event sediment deposition on the floodplain clay pads. There was little apparent correlation between cumulative shortterm deposition and site elevation, distance from channel, longitudinal distance, or fluvial landform type. This may be due to upstream channelization, floodplain complexity, short duration of events, or sedimentload characteristics of low-recurrence interval floods (<2 to 5 years) sampled in this study. Dendrogeomorphic measurements indicated a substantial increase in the mean rate of deposition on the Long Branch Creek floodplain from about 1950 through 1980. Eighty-nine percent of the clay pad monitoring sites and all dendrogeomorphic monitoring sites experienced net positive deposition emphasizing the role of this riparian area as a net sediment storage site.