|On the erodibility of fine-grained sediments in an infilling freshwater system|
|Andersen, T.J.; Houwing, E.J.; Pejrup, M. (2002). On the erodibility of fine-grained sediments in an infilling freshwater system, in: Winterwerp, J.C. et al. (Ed.) (2002). Fine sediment dynamics in the marine environment. Proceedings in Marine Science, 5: pp. 315-328|
|In: Winterwerp, J.C.; Kranenburg, C. (Ed.) (2002). Fine sediment dynamics in the marine environment. Proceedings in Marine Science, 5. Elsevier: Amsterdam. ISBN 0-444-51136-9. XV, 713 pp., more|
|In: Proceedings in Marine Science. Elsevier: Amsterdam. ISSN 1568-2692, more|
erosion threshold; erosion rate; sediment settling; Hollandsch Diep; The Netherlands
The credibility of fine-grained sediments from the Hollandsch Diep freshwater system has been measured using a portable EROMES system. The erosion experiments were carried out on natural sediment surfaces sampled with a box-corer. The measured erosion thresholds varied between 0.16 and 0.70 N m(-2). The erosion thresholds were positively correlated to the dry density of the bed material (r(2) = 0.33) whereas no significant dependence was found on either grain size, organic content or chlorophyll a content. The measured erosion rates varied between 0.04 and 1.68 g m(-2) s(-1) and a strong positive correlation with bed shear stress was observed, The equivalent settling diameters of the eroded material were generally 5 to 10 times larger than that of the primary particles which shows that the material was eroded as aggregates. However, a strong positive correlation between the two settling diameters (r(2) = 0.74) also indicates that the coarser modes of the primary grain size distributions affect size or density of the faster settling aggregates. The lack of corrolation between the credibility and organic content and chlorophyll a content indicates that microphytobenthos is not significantly modifying the erodibility of the sediments at the study sites. The macrofaunal community is also poorly developed with few species and small numbers of individuals and it is concluded that the credibility is mainly controlled by accumulation rate, dry density of the bed material and perhaps maximum current velocity at the sites. This is further supported by the similarity with earlier measurements carried out on settled beds in laboratories.