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Summary: This paper presents a comprehensive review of sediment transport in ice-affected rivers by documenting a range of unique ice and sediment transport processes. In cold regions during winter, high sediment transport rates can occur under specific ice conditions, even if the channel discharge is low. River ice directly displaces and carries sediment, and some ice processes can move boulder-sized sediment, contributing to the sculpting of river channels in ways water alone could not. Special attention is directed to the ice breakup period, during which most dynamic ice processes take place and when sediment supply to river channels is maximized. Also discussed are the time and space scales over which ice processes affect sediment transport. Moreover, a global framework that describes the interconnectivity of climate, river discharge, channel morphology, in-stream hydraulics, and sediment transport response is proposed. Within this framework, ice processes are given a central function, as they influence and are affected by sediment transport, hydrological conditions, and channel morphology. A segment of this work reviews and explores the interconnectivity between river ice processes and river discharge as well as between river ice processes and channel morphology. The proposed framework represents a practical tool for a wide range of cold region river scientists and engineers, particularly in light of climate change. [Copyright &y& Elsevier]

Abstract: In order to assess the extent of sediment connectivity between uplands and lowlands and to quantify the processes of in-channel deposition and remobilization, measurements of suspended sediment fluxes were conducted in a nested rural catchment of the Mexican Volcanic Belt. Data were collected over one year at three upland sites (3 to 12km2) and two downstream stations (390–630km2). Our results show that a structural discontinuity in the catchment (i.e. abrupt slope decrease at the junction between piedmonts and the alluvial plain from 2 to 10% to<0.1%) could be compensated by functional continuity during floods. Direct conveyance of fine sediment to the outlet occurred when a high stream transport capacity was reached. Erosion of the streambed was observed on various occasions and accounted for up to 50% of the flux leaving the catchment during one event. Conversely, temporary in-channel storage was apparent on other occasions, amounting to up to 52% of the flux recorded upstream during one storm. These two distinct behaviours were approximately equally distributed along the rainy season and strongly driven by the extent of coupling between surface and subsurface water. This work indeed highlights the role of baseflow spatial variations in determining the extent of lowland sediment conveyance. Riverbed erosional processes occurred when large differences in pre-event baseflow values (i.e. at least a twofold longitudinal increase) were observed between the 5-km distant lowland stations. Our findings outline the importance of systematically taking into consideration the baseflow parameter in research focusing on fine sediment transport across scales. [Copyright &y& Elsevier]

Abstract: Overwash is an important process in barrier island evolution and its effects on the barrier morphology and sedimentology have been widely studied. However, the short-term sediment dynamics of overwash processes are not well known due to the lack of specific field studies. This paper presents field data that clarify the sedimentary dynamics of overwash processes on different washover morphologies, and determine the factors leading to non-storm overwash occurrence. Two fieldwork campaigns were undertaken during overwash events: GO.1 (winter of 2001), and GO.3 (winter of 2003), on western Barreta Island (Algarve, Portugal). The fieldwork included measurements of oceanographic conditions, overwash flows, morphology variations, mixing depth and sediment transport paths using tracers. The sediment dynamics induced by overwash varied according to the washover morphology (washover plain versus washover lobe). The sediment transport inside the washover plain was different for the two fieldwork campaigns (average mixing depth of 13cm for GO.1 and 6cm for GO.3); however it had similar main stages: Stage 1 — crest accretion, Stage 2 — onshore transport, and Stage 3 — dynamic equilibrium. The sediment transport inside the washover lobe can be characterised by one onshore flow stage, with erosion of the mouth and channel, and accretion on the washover fan. The main factors governing the occurrence of non-storm overwash in the study area were the combined occurrence of: (1) typical winter waves, (2) spring high tides, (3) washover crest below the high-tide level +2m, and (4) absence of prominent beach berm. This study proved that when the proper conditions are generated, non-storm overwash has sediment transport comparable to storm overwash and therefore may be significant for barrier evolution. Further field studies of overwash are needed, principally for more detailed overwash flow velocity measurements, high-frequency morphologic surveys, and barrier groundwater measurements. [Copyright &y& Elsevier]