Needle ice processes and sediment mobilization on river banks: the River Ilston, West Glamorgan, UK

摘要: Abstract This paper examines the role of needle ice processes in bank erosion system a site on River Ilston, West Glamorgan, South Wales, UK. Bank retreat rates were monitored with pins over 2.25 year period. Concurrent detailed data also obtained river flow levels and ambient air stream temperatures. Unique thermal regimes are presented, along rare information morphological properties sediment yield characteristics growths. Needle occurred even mild freezing temperatures if sufficient moisture was present, average growth approximately 1 mm h −1 . material incorporation mobilization within significant: yields up to 4.02 kg m −2 face observed, represented between 32% 43% total recorded. Most incorporated when became stressed (because overrapid cooling and/or limited supplies), which supports models Outcalt Fukuda. Four mechanisms direct transport banks identified: particle fall, sediment-laden rivulets, sliding failures, toppling failures. However, indirect, preparatory frost disturbance surfaces is emphasized, enhanced fluvial takes place materials have first been conditioned by frost-related noted. Both indirect effects expressed simple conceptual model number important linkages examined. Combinations action subsequent fluid entrainment weakened appear be dominant mechanism for here. Pronounced persistent erosional notches lower parts profile showing that, winter, single, low-magnitude, events can effect significant channel width adjustment