TY - JOUR
T1 - Development of layered sediment structure and its effects on pore water transport and hyporheic exchange
AU - Packman, Aaron I.
AU - Marion, Andrea
AU - Zaramella, Mattia
AU - Chen, Cheng
AU - Gaillard, Jean François
AU - Keane, Denis T.
PY - 2006/12
Y1 - 2006/12
N2 - Hyporheic exchange is known to provide an important control on nutrient and contaminant fluxes across the stream-subsurface interface. Similar processes also mediate interfacial transport in other permeable sediments. Recent research has focused on understanding the mechanics of these exchange processes and improving estimation of exchange rates in natural systems. While the structure of sediment beds obviously influences pore water flow rates and patterns, little is known about the interplay of typical sedimentary structures, hyporheic exchange, and other transport processes in fluvial/alluvial sediments. Here we discuss several processes that contribute to local-scale sediment heterogeneity and present results that illustrate the interaction of overlying flow conditions, the development of sediment structure, pore water transport, and stream-subsurface exchange. Layered structures are shown to develop at several scales within sediment beds. Surface sampling is used to analyze the development of an armor layer in a sand-and-gravel bed, while innovative synchrotron-based X-ray microtomography is used to observe patterns of grain sorting within sand bedforms. We show that layered bed structures involving coarsening of the bed surface increase interfacial solute flux but produce an effective anisotropy that favors horizontal pore water transport while limiting vertical penetration.
AB - Hyporheic exchange is known to provide an important control on nutrient and contaminant fluxes across the stream-subsurface interface. Similar processes also mediate interfacial transport in other permeable sediments. Recent research has focused on understanding the mechanics of these exchange processes and improving estimation of exchange rates in natural systems. While the structure of sediment beds obviously influences pore water flow rates and patterns, little is known about the interplay of typical sedimentary structures, hyporheic exchange, and other transport processes in fluvial/alluvial sediments. Here we discuss several processes that contribute to local-scale sediment heterogeneity and present results that illustrate the interaction of overlying flow conditions, the development of sediment structure, pore water transport, and stream-subsurface exchange. Layered structures are shown to develop at several scales within sediment beds. Surface sampling is used to analyze the development of an armor layer in a sand-and-gravel bed, while innovative synchrotron-based X-ray microtomography is used to observe patterns of grain sorting within sand bedforms. We show that layered bed structures involving coarsening of the bed surface increase interfacial solute flux but produce an effective anisotropy that favors horizontal pore water transport while limiting vertical penetration.
KW - Fluvial processes
KW - Hyporheic exchange
KW - Sediment structure
KW - Sediment transport
KW - Solute transport
KW - Streambeds
KW - Streams and rivers
KW - Surface-groundwater interactions
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U2 - 10.1007/s11267-006-9057-y
DO - 10.1007/s11267-006-9057-y
M3 - Article
AN - SCOPUS:33845953951
SN - 1567-7230
VL - 6
SP - 433
EP - 442
JO - Water, Air, and Soil Pollution: Focus
JF - Water, Air, and Soil Pollution: Focus
IS - 5-6
ER -