Preprints
https://doi.org/10.5194/hess-2019-194
https://doi.org/10.5194/hess-2019-194

  10 May 2019

10 May 2019

Review status: this preprint was under review for the journal HESS but the revision was not accepted.

Drainage of soft cohesive sediment with and without Phragmites australis as an ecological engineer

Rémon M. Saaltink1,6, Maria Barciela-Rial2, Thijs van Kessel3, Stefan C. Dekker1,5, Hugo J. de Boer1, Claire Chassange2, Jasper Griffioen1,4, Martin J. Wassen1, and Johan C. Winterwerp2 Rémon M. Saaltink et al.
  • 1Department of Environmental Sciences, Copernicus Institute of Sustainable Development, Utrecht University, The Netherlands
  • 2Section of Environmental Fluid Mechanics, Delft University of Technology, The Netherlands
  • 3Deltares, P.O. Box 177, 2600 MH Delft, The Netherlands
  • 4TNO Geological Survey of the Netherlands, The Netherlands
  • 5Faculty of Management, Science and Technology, Open University, Heerlen, The Netherlands
  • 6HAS University of Applied Sciences, ‘s-Hertogenbosch, the Netherlands

Abstract. Conventional drainage techniques are often used to speed up consolidation of fine sediment. These techniques are relatively expensive, are invasive and often degrade the natural value of the ecosystem. This paper focusses on exploring an alternative approach that uses natural processes, rather than a technological solution, to speed up drainage of soft cohesive sediment. In a controlled column experiment, we studied how Phragmites australis can act as an ecological engineer that enhances drainage, thereby potentially promoting sediment consolidation. We measured the dynamics of pore water pressures at 10 cm depth intervals during a 129-day period in a column with and without plants, while the water level was fixed. Water loss via evaporation was measured using Mariotte bottles and the photosynthetic processes – including plant transpiration – were measured with a LICOR photosynthesis system. The results show that several processes initiated by P. australis interfere with the physical processes involved in sediment drainage and consolidation. Phragmites australis effectively altered the pore pressure gradient via water extraction, especially between 40 and 60 cm from the bottom of the column. In this zone, daily cycles in pore pressures were observed which could directly be linked to the diurnal cycle of stomatal gas exchange. On average, water loss via evaporation and transpiration of leaves of P. australis amounted to 3.9 mm day−1, whereas evaporation of bare soil amounted on average to 0.6 mm day−1. Moreover, the depth-averaged hydraulic conductivity increased on average by 40 % in presence of P. australis. The results presented in this study provide information needed for predictive modelling of plants as ecological engineers to speed up soil forming processes in the construction of wetlands with soft cohesive sediment.

Rémon M. Saaltink et al.

 
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Status: closed
Status: closed
AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment
Printer-friendly Version - Printer-friendly version Supplement - Supplement

Rémon M. Saaltink et al.

Rémon M. Saaltink et al.

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Short summary
This paper focusses on exploring an alternative approach that uses natural processes, rather than a technological solution, to speed up drainage of soft sediment. In a controlled column experiment, we studied how Phragmites australis can act as an ecological engineer that enhances drainage. The presented results provide information needed for predictive modelling of plants as ecological engineers to speed up soil forming processes in the construction of wetlands with soft cohesive sediment.