Dynamics of river sediments in forested headwater streams: Plynlimon

Long term studies of fluvial sediment processes in the Plynlimon catchments have contributed to the assessment and quantification of plantation forestry impacts in British upland catchments, at all stages of the forest cycle. The results from the Plynlimon studies are placed in the context of the observed impacts of particular forest practices and studies of forestry effects on sediment transport elsewhere in the world. The effects associated with drain excavation, ploughing, track construction, ground and channel disruption are outlined for both bedload and, particularly, for suspended load. Finally, recent data on sediment yields from 1995 to 1997 at Plynlimon are reported and discussed in the light of longer-term sediment yield estimates. This paper also provides background information relevant to other sediment process studies which use data from the main Plynlimon sediment monitoring network

Sediment sources in the Upper Severn catchment: a fingerprinting approach

Suspended sediment sources in the Upper Severn catchment are quantified using a composite fingerprinting technique combining statistically-verified signatures with a multivariate mixing model. Composite fingerprints are developed from a suite of diagnostic properties comprising trace metal (Fe, Mn, AI), heavy metal (Cu, Zn, Pb, Cr, Co, Ni), base cation (Na, Mg, Ca, K), organic (C, N), radiometric (137Cs, 210Pb), and other (total P) determinands. A numerical mixing model, to compare the fingerprints of contemporary catchment source materials with those of fluvial suspended sediment in transit and those of recent overbank floodplain deposits, provides a means of quantifying present and past sediment sources respectively. Sources are classified in terms of eroding surface soils under different land uses and channel banks. Eroding surface soils are the most important source of the contemporary suspended sediment loads sampled at the Institute of Hydrology flow gauging stations at Plynlimon and at Abermule. The erosion of forest soils, associated with the autumn and winter commercial activities of the Forestry Commission, is particularly evident. Reconstruction of sediment provenance over the recent past using a sediment core from the active river floodpiain at Abermule, in conjunction with a 137Cs chronology, demonstrates the significance of recent phases of afforestation and deforestation for accelerated catchment soil erosion

Composite fingerprinting of the spatial source of fluvial suspended sediment : a case study of the Exe and Severn river basins, United Kingdom

Abstract Fingerprinting of fluvial suspended sediment sources using a range of physical and chemical properties has been shown by a number of studies to offer a valuable alternative to the intensive monitoring techniques traditionally used to determine suspended sediment sources in drainage basins. Information derived from such an approach has important applications in the establishment of sediment budgets, in the development of sediment and pollution control strategies and in erosion monitoring studies. Emphasis to date has focused primarily upon both qualitative and quantitative identification of source type, as opposed to spatial source, using both single - and multi-parameter fingerprints. Multi-parameter composite fingerprints provide a greater degree of source discrimination, by affording greater consistency to any calculations. The results of a study aimed at assessing the potential for using composite fingerprints to identify the spatial source of suspended sediment in the basins of the River Exe (601 km2) and River Severn (4 325 km2), UK, are presented. Multivariate Discriminant Function Analysis is employed to identify composite fingerprints capable of distinguishing potential spatial sources of suspended sediment. The results of the Discriminant Analysis are then used in a mixing model to provide preliminary estimates of the relative contributions of a number of distinct spatial sources to the overall sediment loadRésumé Dans de nombreuses études, l'utilisation de "fiches d'identité" pour retrouver l'origine de sédiments en suspension, basée sur une large gamme de propriétés physiques et chimiques de ces sédiments, a montré qu'elle était une alternative efficace aux techniques traditionnelles de mesures intensives. Les renseignements tirés de ce fichage peuvent être utilisés pour l'établissement de budgets sédimentaires, pour la mise au point de stratégie de contrôle des transports de sédiments et de pollution, ainsi que pour les études de surveillance de l'érosion. A ce jour, la plupart des études établissant des "fiches d'identité" ont insisté sur l 'identification qualitative et quantitative des types de sources, par opposition aux sources géographiques, en utilisant des caractérisations portant sur des paramètres uniques et multiples. Il semble que le fichage multiparamètre fournisse un degré plus grand de définition de la zone-source potentielle car il s'accompagne d'une uniformité plus grande valable pour tous les calculs. Nous présentons les résultats d'une étude dont le but était d'estimer le potentiel en fichages multiparamètres susceptibles de permettre l'identification de la source géographique des sédiments en suspension dans les eaux de la rivière Exe (601 km2) et de la Severn (4 325 km2). Nous avons utilisé l'analyse multivariée pour identifier les "fiches " multiparamètres capables de nous permettre de distinguer les sources spatiales potentielles de sédiments en suspension. Les résultats des analyses discriminantes ont ensuite été utilisés dans un modèle de mélange afin d'établir des évaluations préliminaires des contributions respectives d'un certain nombre de sources géographiques distinctes dans l'ensemble de la charge sédimentaire.Collins Adrian L., Walling D.E, Leeks G.J. L. Composite fingerprinting of the spatial source of fluvial suspended sediment : a case study of the Exe and Severn river basins, United Kingdom. In: Géomorphologie : relief, processus, environnement, Octobre 1996, vol. 2, n°2. pp. 41-53

Land–ocean interaction: processes, functioning and environmental management from a UK perspective: an introduction

This paper provides a foreword to a special edition of Science of the Total Environment concerned with land–ocean interaction from a UK perspective as linked to processes, functioning and environmental management. The volume structure is presented together with an outline of the nature of the individual papers. The areas covered are: (1) freshwater chemistry, (2) riverine sedimentology, (3) tidal river, estuarine and coastal chemistry, (4) estuarine and coastal sediments and (5) shelf-sea-ocean linkages. The foreword provides as an introductory link to the broader perspectives of contemporary UK research in this area, which comes in a conclusions paper at the end of the volume