Measuring sediment transport and bed disturbance with tracers on a mixed beach

Abstract A new tracer deployment method is applied to the problem of resolving rates and patterns of littoral sediment transport on mixed beaches. We applied the method at the morphologically complex, meso-tidal beach fringing the Elwha River delta, Washington. Clasts were transformed into tracers using Radio Frequency Identifier (RFID) tags. These tracers were deployed in and on the bed along a cross-shore oriented beach transect. Along- and cross-shore variations in tracer velocity were used to estimate sediment transport patterns, including the depth and cross-sectional area of the disturbed bed and bulk alongshore transport rates. We found that the peak bed disturbance averaged 22% of the tidal maximum significant wave height and that tracer velocity declined approximately logarithmically with depth in the bed. Across all deployments the maximum alongshore tracer velocity occurred between 1.0 and 2.0 m above Mean Lower Low Water (MLLW), corresponding to elevations 0.3 m below and 0.7 m above Mean Sea Level (MSL) at this location. Alongshore bulk sediment transport rates estimated from the advection of tracers ranged from 1.1 to 173.1 m3/d under significant wave heights of 0.1 to 2.1 m and these transport rates related linearly to measured wave energy transport. Both the volumetric sediment transport rates and a CERC-type k coefficient derived from the results agreed well with results from other published studies.

[1]  M. Lorang.  Predicting Threshold Entrainment Mass for a Boulder Beach , 2000 .

[2]  R. Nicholls,et al.  Longshore Transport of Pebbles: Experimental Estimates of K , 1991 .

[3]  J. Shulmeister,et al.  A field based classification scheme for gravel beaches , 2002 .

[4]  T. Coates,et al.  Sediment Transport Processes on Mixed Beaches: A Review for Shoreline Management , 2001 .

[5]  Ian L Turner,et al.  Swash zone sediment transport, step dynamics and morphological response on a gravel beach , 2010 .

[6]  G. Brian,et al.  Depth of Activity, Sediment Flux, and Morphological Change in a Barred Nearshore Environment , 1980 .

[7]  P. DeVries.  Bedload layer thickness and disturbance depth in gravel bed streams , 2002 .

[8]  Daniel M. Hanes,et al.  Intermittent sediment suspension and its implications to sand tracer dispersal in wave-dominated environments , 1988 .

[9]  Michael G. Hughes,et al.  Breaker turbulence and sediment suspension in the surf zone , 2010 .

[10]  Andrew Chadwick,et al.  A review and assessment of longshore sediment transport equations for coarse-grained beaches , 2000 .

[11]  Jonathan C. Allan,et al.  The use of Passive Integrated Transponder (PIT) tags to trace cobble transport in a mixed sand-and-gravel beach on the high-energy Oregon coast, USA , 2006 .

[12]  J. Warrick,et al.  Beach morphology and change along the mixed grain-size delta of the dammed Elwha River, Washington , 2009 .

[13]  Corinne Le Quéré,et al.  Climate Change 2013: The Physical Science Basis , 2013 .

[14]  D. Mosher,et al.  Late Quaternary deglaciation and sea-level history of eastern Juan de Fuca Strait, Cascadia , 2004 .

[15]  P. Elmore,et al.  A review of heterogeneous sediments in coastal environments , 2008 .

[16]  G. Anfuso.  Sediment-activation depth values for gentle and steep beaches , 2005 .

[17]  B. Castelle,et al.  Improvement of sand activation depth prediction under conditions of oblique wave breaking , 2008 .

[18]  D. Inman,et al.  Longshore sand transport on beaches , 1970 .

[19]  E. Schreiner,et al.  Baseline Studies in the Elwha River Ecosystem Prior to Dam Removal: Introduction to the Special Issue , 2008 .

[20]  Philip D. Osborne,et al.  Transport of gravel and cobble on a mixed-sediment inner bank shoreline of a large inlet, Grays Harbor, Washington , 2005 .

[21]  Paul A. Carling,et al.  Coarse sediment tracing technology in littoral and fluvial environments a review , 2002 .

[22]  D. Buscombe,et al.  Morphological change and sediment dynamics of the beach step on a macrotidal gravel beach , 2008 .

[23]  Judith K. Haschenburger,et al.  Substrate indices as indicators of interstitial pore space in gravel‐bed channels , 2009 .

[24]  Gerhard Masselink,et al.  Short‐term morphological change and sediment dynamics in the intertidal zone of a macrotidal beach , 2007 .

[25]  Michele Capobianco,et al.  Variability of shore and shoreline evolution , 2002 .

[26]  J. C. Crowe,et al.  Experimental study of the transport of mixed sand and gravel , 2001 .

[27]  Jonathan A. Warrick,et al.  Observations of coarse sediment movements on the mixed beach of the Elwha Delta, Washington , 2011 .

[28]  W. Collins,et al.  Global climate projections , 2007 .

[29]  D. Buscombe,et al.  Cobble cam: grain‐size measurements of sand to boulder from digital photographs and autocorrelation analyses , 2009 .

[30]  Uwe Dornbusch,et al.  Ground Survey Methods for Mixed Sand and Gravel Beaches in Intertidal Environments: A Comparison , 2010 .

[31]  P. Kench,et al.  Hydrodynamics and morphological adjustment of a mixed sand and gravel beach, Torere, Bay of Plenty, New Zealand , 2006 .

[32]  Robert T. Guza,et al.  Edge waves and beach cusps , 1975 .

[33]  Philip D. Osborne,et al.  Seasonal patterns of coarse sediment transport on a mixed sand and gravel beach due to vessel wakes, wind waves, and tidal currents , 2009 .

[34]  Carlos M. Toro-Escobar,et al.  Equal mobility of gravel in streams: The remains of the day , 2002 .

[35]  P. Atkinson,et al.  Number of tracers required for the measurement of longshore transport distance on a shingle beach , 2007 .

[36]  Paul D. Komar,et al.  Beach Processes and Sedimentation , 1976 .

[37]  Peter N. Adams,et al.  Intertidal sand body migration along a megatidal coast, Kachemak Bay, Alaska , 2007 .

[38]  Maurice L. Schwartz,et al.  Encyclopedia of coastal science , 2005 .

[39]  Ó. Ferreira,et al.  Field observations of sand-mixing depths on steep beaches , 1997 .