Georg Meier,Thomas Zumbroich,Jackson Roehrig, Universidade de Ciências Aplicadas Colônia, Instituto de Tecnologias nos Trópicos e Subtrópicos (ITT), georg.meier@fh-koeln.de
Abstract
Hydromorphological deficits of European rivers and creeks are a major reason for not reaching the good ecological status according to the European Water Framework Directive. One of these hydromorphological pressures is the clogging of river beds by fine sediments (colmation) and its deleterious effects on benthic ecology. The mitigation of these effects requires the assessment of colmation levels by analysing temporal and spatial variations on a river basin scale. The aim of this study is to formulate a colmation assessment approach based on a combination of hydrological / hydraulic modelling, sediment sample taking and colmation mapping. We tested the reliability of these methods by comparing their outputs with invertebrate samplings. The combination of sampling site selection though interpretation of a pollution-runoff-model, freeze core sampling, sediment traps and colmation mapping provided appropriate information to assess the colmation level on a river basin scale aiming at the prioritization of mitigation messures. Notwithstanding, the lack of standardized sampling methods and missing quality guidelines regarding colmation levels impede appropriate assessment of fine sediment pressure on benthic invertebrates. Great effort is still needed to set these standards and provide river basin managers with adequate hands-on tools to assess colmation.
Keywords colmation, sediment sampling methods, benthic ecology