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© The Author(s), 2018. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Scientific Reports 8 (2018): 15219, doi:10.1038/s41598-018-33283-4., This Article corrects an error in Equation 1

© The Author(s), 2018. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Scientific Reports 8 (2018): 9478, doi:10.1038/s41598-018-26948-7., Tidal wetlands produce long-term soil organic carbon (C) stocks. Thus for carbon accounting purposes, we need accurate and precise information on the magnitude and spatial distribution of those stocks. We assembled and analyzed an unprecedented soil core dataset, and tested three strategies for mapping carbon stocks: applying the average value from the synthesis to mapped tidal wetlands, applying models fit using empirical data and applied using soil, vegetation and salinity maps, and relying on independently generated soil carbon maps. Soil carbon stocks were far lower on average and varied less spatially and with depth than stocks calculated from available soils maps. Further, variation in carbon density was not well-predicted based on climate, salinity, vegetation, or soil classes. Instead, the assembled dataset showed that carbon density across the conterminous united states (CONUS) was normally distributed, with a predictable range of observations. We identified the simplest strategy, applying mean carbon density (27.0 kg C m−3), as the best performing strategy, and conservatively estimated that the top meter of CONUS tidal wetland soil contains 0.72 petagrams C. This strategy could provide standardization in CONUS tidal carbon accounting until such a time as modeling and mapping advancements can quantitatively improve accuracy and precision., Synthesis efforts were funded by NASA Carbon Monitoring System (CMS; NNH14AY67I), USGS LandCarbon and the Smithsonian Institution. J.R.H. was additionally supported by the NSF-funded Coastal Carbon Research Coordination Network while completing this manuscript (DEB-1655622). J.M.S. coring efforts were funded by NSF (EAR-1204079). B.P.H. coring efforts were funded by Earth Observatory (Publication Number 197).

Approved for public release; distribution is unlimited. ERDC/TN DOER-D21 November 2018 Evaluation of Capacitance Staffs to Measure Vertical Accretion in Tidal Environments by Brandon M. Boyd and Duncan B. Bryant PURPOSE: This Dredging Operations and Environmental Research (DOER) Technical Note (TN) describes the effect of sediment deposition on water-level measurements taken via capacitance staff. During a field study, capacitance-type staffs used for wave measurement were buried by sediment. Analysis of this field data resulted in water-level minimums increasing through time. It was hypothesized that over time, the staffs were recording not the minimum water level but the increasing bed elevation. Laboratory experiments were designed to observe any effect of sediment burial on water-level measurements made using capacitance-type wave staffs. INTRODUCTION Motivation. Vertical accretion and surface elevation change are common metrics used in studying the geomorphology and viability of tidal marshes (Stoddart et al. 1989; Boyd and Sommerfield 2016). Methods of measurement include sediment traps and marker horizons that require installation and physical sampling, ground- or aerial-based survey methods that require repeat surveys at a desired temporal resolution, and geochemical methods that require significant analytical investment. Resolution of the accretion measurement using such approaches is limited to sampling frequency and thus often does not capture deposition and erosion associated with tidal, wind, and storm events. The contribution of such events as well as seasonal variations in emergent biomass to the accretion process is of utmost interest in ecology and numerical modeling (Fagherazzi et al. 2012). This study describes the serendipitous collection of a time series of surface elevation change by capacitance-type wave staffs and a laboratory evaluation aimed at determining such staffs’ ability to measure accretion in tidal marshes. The use of capacitance to

Approved for public release; distribution is unlimited. ERDC/TN-DOER-D20 May 2018 Quantifying Sediment Accumulation and Accretion using 210Pb and 137Cs by Brandon M. Boyd PURPOSE: This Dredging Operations and Environmental Research (DOER) Program Technical Note (TN) describes the use of the radionuclides 210Pb and 137Cs to measure rates of sediment accumulation and accretion and provides recommendations for best practices in field collection and laboratory analysis for U.S. Army Corps of Engineers (USACE) projects. BACKGROUND: The ability to quantify the flux of sediment to an area and the corresponding change in bed or surface elevation is useful in both sediment dynamic and hydrodynamic studies. Rates of accretion and accumulation can be used to determine past rates of contaminant and nutrient burial, constrain sediment budgets, identify areas experiencing long-term sedimentation, evaluate site-wide variability in sedimentation, and validate sediment transport models. Numerous radionuclides can be employed as tracers or can provide age control in a broad range of geophysical studies. This TN focuses on the quantification of sediment accumulation and accretion rates using lead-210 (210Pb; half-life = 22.2 years) and cesium-137 (137Cs; half-life = 30.7 years) methods. These methods have been successfully applied in a variety of terrestrial, coastal, and marine environments (Baskaran and Naidu 1995; Baskaran et al. 2015; Boyd et al. 2017). Estuarine sediment budgets, reservoir infilling, and engineering methods to increase wetland sedimentation are common focuses of USACE projects which can utilize radionuclide-based rates of sediment accumulation and accretion. The DOER Program supports ongoing research to evaluate the accretion dynamics of thin-layer placement and restored marshes. Sediment Accumulation and Accretion Rates. Sediment accumulation (mass/area/time) occurs when sediments are transported by a fluid (air or water) and subsequently deposited due to a redu

ERDC/CHL TR-17-12 Sediment Dynamics in a Vegetated Tidally Influenced Interdistributary Island: Wax Lake, Louisiana Coastal and Hydraulics Laboratory Richard Styles, Duncan Bryant, Joe Gailani, Jarrell Smith, Brandon M. Boyd, and Greg Snedden July 2017 Approved for public release; distribution is unlimited. The U.S. Army Engineer Research and Development Center (ERDC) solves the nation’s toughest engineering and environmental challenges. ERDC develops innovative solutions in civil and military engineering, geospatial sciences, water resources, and environmental sciences for the Army, the Department of Defense, civilian agencies, and our nation’s public good. Find out more at www.erdc.usace.army.mil. To search for other technical reports published by ERDC, visit the ERDC online library at http://acwc.sdp.sirsi.net/client/default. ERDC/CHL TR-17-12 July 2017 Sediment Dynamics in a Vegetated Tidally Influenced Interdistributary Island: Wax Lake, Louisiana Richard Styles, Duncan Bryant, Joe Gailani, Jarrell Smith, and Brandon M. Boyd Coastal and Hydraulics Laboratory U.S. Army Engineer Research and Development Center 3909 Halls Ferry Road Vicksburg, MS 39180-6199 Gregg Snedden Wetland and Aquatic Research Center 624 N. Fourth St. U.S. Geological Survey Baton Rouge, LA 70803 Final report Approved for public release; distribution is unlimited. Prepared for U.S. Army Engineer Research and Development Center 3909 Halls Ferry Road Vicksburg, MS 39180-6199 Under Work Unit ERDC-219CDR-14-TT-Sediment Management, “Section 219 Center Directed Research Program” ERDC/CHL TR-17-12 ii Abstract River deltas are maintained by a continuous supply of terrestrial sediments that provide critical land-building material to help sustain and protect coastal communities. In order to examine the mechanisms of sediment delivery, a field study was conducted at Wax Lake Delta located in St. Mary Parish, LA. Instrumented platforms equipped with wave, current, tide and sediment sensors were installed