103 research outputs found
L'érosion des sols agricoles : J. Boardman, I.D.L. Foster et J.A. Dearing (eds.), Soil Erosion on Agricultural Land
No full textCosandey Claude. L'érosion des sols agricoles : J. Boardman, I.D.L. Foster et J.A. Dearing (eds.), Soil Erosion on Agricultural Land. In: Annales de Géographie, t. 100, n°560, 1991. pp. 464-465
Sediment fingerprinting as a tool for interpreting long-term river activity: The Voidomatis basin, Northwest Greece
No full textSediment Sources and Terminal Pleistocene Geomorphological Processes Recorded in Rockshelter Sequences in North-west Greece
No full textSediment fingerprinting as a tool for interpreting long-term river activity: The Voidomatis basin, Northwest Greece
No full textSediment Sources and Terminal Pleistocene Geomorphological Processes Recorded in Rockshelter Sequences in North-west Greece
No full textThe potential for paleolimnology to determine historic sediment delivery to rivers
No full textEstablishment of water quality criteria to
guide catchment sediment management is required by
the European Union (EU) Water Framework Directive.
The topic, however, is hotly contested among scientists
and policy makers. Existing legislation with regard to
fine sediment was set by the EU Freshwater Fish
Directive. Its guideline, i.e. mean annual suspended
sediment concentration, is 25 mg l-1. Such a static
target fails to capture the episodic nature of sediment
transport. Furthermore, application of such global
standards is inappropriate for a pollutant that is
strongly controlled by spatial variation in key catchment
drivers. Paleolimnology offers an approach for
assessing background sediment pressures on watercourses,
enabling determination of values for times
pre-dating agricultural intensification.Wepropose that
Modern Background Sediment Delivery to Rivers
(MBSDR) across England and Wales can be determined
using paleolimnology to quantify maximum
feasible sediment reduction. No management programme
should aim to reduce sediment loss to values
below those resulting from background, natural physiographic
and/or hydrological controls. Lacking generic
tools to quantify process linkages between
sediment pressures and biological impact, we propose
that MBSDR could be taken to represent ecological
demand for sediment inputs into watercourses required
to support healthy aquatic habitats. In situations where
generic tools exist for coupling sediment pressures and
ecological impacts, assessment of MBSDR could be
used to correct the gap between current or future
projected sediment loss and biological condition.
Existing paleolimnological data on sediment yields
across England and Wales are presented to illustrate
the approach and provide preliminary national estimates
of MBSDR. We briefly consider the basis for
reconstructing sediment yields using a paleolimnological
approach and analyse temporal trends in published sediment yield, inferred for a range of landscape types.
We also attempt to correlate sediment accumulation
rates (SARs) with sediment yields to extend the
MBSDR data base. Preliminary maps were generated
to identify regions where further sediment yield data
are needed to produce a more robust estimate of the
spatial distribution of MBSDR across England and
Wales
Sediment fingerprinting as a tool for interpreting long-term river activity: The Voidomatis basin, Northwest Greece
No full textSediment targets for informing river catchment management: international experience and prospects
No full textSediment plays a pivotal role in determining the physical, chemical and biological integrity of aquatic ecosystems. A range of factors influences the impacts of sediment pressures on aquatic biota, including concentration, duration of exposure, composition and particle size. In recognition of the need to assess environmental status for sediment and mitigate excessive sediment pressures on aquatic habitats, both water column and river substrate metrics have been proposed as river sediment targets. Water column metrics include light penetration, turbidity, sediment concentration summary statistics and sediment regimes. Substrate metrics include embeddedness, the fredle index and riffle stability. Identification of meaningful numeric targets along these lines has, however, been undermined by various issues including the uncertainty associated with toxicological dose-response profiles and the impracticalities of deploying statistically robust sampling strategies capable of supporting catchment-scale targets. Many of the thresholds reported are based on correlative relationships that fail to capture the specific mechanisms controlling sediment impacts on aquatic habitats and are stationary in nature. Temporal windows represented by the key life stages of specific species must be given greater emphasis. Given such issues and the need to support the revision of sediment targets for river catchment management, it is proposed that greater emphasis should be placed on developing generic modelling toolkits with the functionality for coupling current or future projected sediment regimes with biological response for a range of biota. Such tools should permit the identification of river catchment-specific targets within a national context, based on biological effect and incorporate sufficient flexibility for utilizing updated physical, chemical, biological and catchment attribute data. Confidence will continue to be required in compliance screening to ensure cost-effective management programmes for avoiding disproportionate investment in impacted river catchments
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