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This study presents a new method to examine long-term dynamics in sediment yield using time-varying sediment-discharge rating curves. Dynamic linear models (DLMs) are introduced as a time series filter that can assess how the relationship between streamflow and sediment concentration or load changes over time in response to a wide variety of natural and anthropogenic watershed disturbances or long-term changes. The filter operates by updating parameter values using a recursive Bayesian design that responds to 1 day-ahead forecast errors while also accounting for observational noise. The estimated time series of rating curve parameters can then be used to diagnose multiscale (daily-decadal) variability in sediment yield after accounting for fluctuations in streamflow. The technique is applied in a case study examining changes in turbidity load, a proxy for sediment load, in the Esopus Creek watershed, part of the New York City drinking water supply system. The results show that turbidity load exhibits a complex array of variability across time scales. The DLM highlights flood event-driven positive hysteresis, where turbidity load remained elevated for months after large flood events, as a major component of dynamic behavior in the rating curve relationship. The DLM also produces more accurate 1 day-ahead loading forecasts compared to other static and time-varying rating curve methods. The results suggest that DLMs provide a useful tool for diagnosing changes in sediment-discharge relationships over time and may help identify variability in sediment concentrations and loads that can be used to inform dynamic water quality management. log Q s 5 b 0 1 b 1 log Q w 1e (1) or, expressed in the power-law formulation: Key Points: Dynamic linear models (DLMs) are proposed to model time-varying discharge-suspended sediment relationships DLMs are capable of representing changes to sediment yield from abrupt disturbances to a watershed An application in a mountainous watershed in New York reveals interesting flood-induced positive hysteresis in sediment yield

Both human activity and climate change can influence erosion rates and initiate rapid landscape change. Understanding the relative impact of these factors is critical to managing the risks of extreme erosion related to flooding and landslide occurrence. Here we present a 2100 year record of sediment mass accumulation and inferred erosion based on lacustrine sediment cores from Amherst Lake, Vermont, USA. Using deposition from August 2011 Tropical Storm Irene as a modern analogue, we identified distinct event deposits indicative of destructive erosion events. These deposits record a prolonged (multidecadal) interval of enhanced erosion following the initial storm‐induced landscape disturbance. The direct impact of human land cover alteration is minimal in comparison to the more recent twentieth century increase in the occurrence of catastrophic erosion linked to overall wetter conditions that favor high erosion rates and more easily trigger landslides during periods of extreme precipitation.

Lacustrine sediment archives indicate that flooding during Tropical Storm Irene (2011) in the north‐eastern United States caused the most severe erosion of any flood in the historic record, surpassing that of events with greater precipitation and peak discharges. Compared to deposition from historic floods, Irene's event layer was more massive and more enriched in unweathered upland sediments, indicating an anomalously high incidence of mass wasting and sediment entrainment. Precipitation records indicate that neither precipitation intensity nor total accumulation distinguished Irene from less erosive historic floods. However, cumulative precipitation prior to Irene exceeded the 95th percentile of all days in the record. When allowing for non‐stationarity in the twentieth century background precipitation, we find a four‐fold increase in the probability of Irene‐like conditions, where impacts of extreme rainfall are enhanced by high antecedent precipitation. We conclude that irrespective of increases in extreme precipitation, the risk of highly erosive flooding in the region is increasing due to the influence of wetter baseline conditions associated with a changing climate. Copyright © 2015 John Wiley & Sons, Ltd.

Tidal marsh restoration and creation is growing in popularity due to the many and diverse sets of services these important ecosystems provide. However, it is unclear what conditions within constructed settings will lead to the successful establishment of tidal marsh. Here we provide documentation for widespread and rapid

Tidal marsh restoration and creation has been proposed as a tool to build coastal resilience in the face of rising sea level and increasing intensity of coastal storms. However, it is unclear what conditions within constructed settings will lead to the successful establishment of tidal marsh. We used sediment cores and historical geospatial data in the tidal freshwater Hudson River to identify the rapid creation and development of marshes that are sheltered by human-made structures including railroad berms, jetties, and dredge spoil islands. These backwater areas rapidly accumulated clastic material following anthropogenic modification that allowed for transition from tidal mudflat to emergent marsh. In one case, historical aerial photos document this transition occurring in less than 18 years, offering a timeframe for marsh development. Accretion rates for anthropogenic tidal marshes and mudflats average 0.8-1.1 cm yr-1 and 0.6-0.7 cm yr-1 respectively, equivalent to 2-3 times the rate of relative sea level rise as well as the observed accretion rate at a 6000+ year old reference marsh in the study area. Paired historical and geospatial analysis revealed that more than half of all the tidal wetlands on the Hudson are anthropogenic and developed since the industrial era, including two thirds of the emergent cattail marsh. These inadvertently constructed tidal wetlands currently trap roughly 6% of the Hudson River’s sediment load. Results indicate that when sediment is readily available freshwater tidal wetlands can develop relatively rapidly in sheltered estuarine settings, and serve as useful examples to help guide future tidal marsh creation and restoration efforts.

Off‐river coves and embayments provide accommodation space for sediment accumulation, particularly for sandy estuaries where high energy in the main channel prevents significant long‐term storage of fine‐grained material. Seasonal sediment inputs to Hamburg Cove in the Connecticut River estuary (USA) were monitored to understand the timing and mechanisms for sediment storage there. Unlike in freshwater tidal coves, sediment was primarily trapped here during periods of low discharge, when the salinity intrusion extended upriver to the cove entrance. During periods of low discharge and high sediment accumulation, deposited sediment displayed geochemical signatures consistent with a marine source. Numerical simulations reveal that low discharge conditions provide several important characteristics that maximize sediment trapping. First, these conditions allow the estuarine turbidity maximum (ETM) to be located in the vicinity of the cove entrance, which increases sediment concentrations during flood tide. Second, the saltier water in the main channel can enter the cove as a density current, enhancing near‐bed velocities and resuspending sediment, providing an efficient delivery mechanism. Finally, higher salinity water accumulates in the deep basin of the cove, creating a stratified region that becomes decoupled from ebb currents, promoting retention of sediment in the cove. This process of estuarine‐enhanced sediment accumulation in off‐river coves will likely extend upriver during future sea level rise.

Tidal salt marshes are critical protectors of the coast; they buffer against erosion and flooding (Möller et al., 2014), sequester carbon (Chmura et al., 2003), provide habitat to juvenile species and migratory birds (Boesch & Turner, 1984;Hughes, 2004), and filter pollutants and excess nutrients (Sousa et al., 2010). Coastal wetland maintenance involves complex biophysical feedbacks between clastic (i.e., inorganic) sediment supply, nutrients, plant growth, and flooding (Deegan et al., 2012;Kirwan & Megonigal, 2013). Deposition of clastic sediment in the form of clays, silts, and sands allows marshes to accrete faster than would be possible via in-situ organic production alone; thus, the availability and delivery of clastic sediment is a key factor in determining salt marsh resilience to erosion and future sea level rise (e.g.,