Meire, P.

Seuntjens, P.

Temmerman, S.

Van Putte, N.

Verreydt, G.

Open Marine Archive

 116 
Improving groundwater dynamics: A key factor for successful tidal 
marsh restoration? 
Van Putte Niels
1
, Temmerman Stijn
1
, Meire Patrick
1
, Seuntjens Piet
1-2-3
 and Verreydt Goedele
1-4 
1 
University of Antwerp, Universiteitsplein 1C, 2610 Wilrijk, Belgium 
 E-mail: niels.vanputte@uantwerpen.be 
2
 Ghent University, Coupure links 653, 9000 Ghent, Belgium 
3
 VITO nv, Boeretang 200, 2400 Mol, Belgium 
4
  IFLUX, Galileilaan, 2845 Niel, Belgium 
 
Introduction and goals 
 
In the past centuries, many tidal marshes along estuaries and coasts have been embanked to gain 
land for industry and agriculture, leading to severe problems such as an increased flooding risk, loss 
of biodiversity and a deteriorating water quality. Nowadays, numerous of these former marshes are 
being restored to recover their ecosystem functions. There are, however, more and more indications 
that restored tidal marshes do not deliver these ecosystem services to the same extent as natural 
tidal marshes. In particular, we hypothesize that a reduced groundwater flow, caused by historical 
agricultural soil compaction, implies a reduced nutrient cycling and decreased contribution of 
restored marshes to water quality improvement. In a combined field and modelling study, we aim to 
get insight in how groundwater and biogeochemical functioning (e.g. retention of phosphorus and 
nitrogen and export of dissolved silica) are related in natural and restored tidal marshes. In an in situ 
mesocosm experiment, we are currently testing the effect of different soil amendments (see below) 
on groundwater and nutrient dynamics. the ultimate goal of this project is to formulate viable design 
criteria for future tidal marsh restoration projects. 
 
Conducted research 
 
We measured groundwater flow and soil properties in both a natural freshwater tidal marsh (De Plaat) 
and a restored freshwater tidal marsh (Lippenbroek) along the Scheldt. The soil in the restored marsh 
consists of a layer of freshly accreted sediment, underlain by compact relict agricultural soil. Our 
results indicate that groundwater level fluctuations are occurring over a deeper soil profile in the 
natural marsh compared to the restored marsh, where groundwater level fluctuations are restricted 
to the layer of freshly accreted sediment. Using X-ray CT-scans of soil cores, we found that the soil in 
the natural marsh and the upper layer of the restored marsh is intersected by macropores that 
increase the hydraulic conductivity of the sediment, whereas these macropores are absent in the 
compacted agricultural soil. As a result, the compact agricultural soil forms a barrier for groundwater 
flow and puts constraints on the amount of pore water that is exported to the creeks in between tidal 
events. By consequence, nutrient cycling in restored tidal marshes is expected to be negatively 
affected. 
 
Ongoing mesocosm experiment 
 
In a polder area, three different soil treatments were locally applied: ploughing, ploughing + adding 
reed cuttings and ploughing + adding wood chips. In each of the treatment plots and in one untreated 
(blanco) plot, an undisturbed soil monolith of 150 cm wide and 75 deep was excavated. The monoliths 
were then placed in a mesocosm construction in the Scheldt river. At high tide, the monoliths inundate 
and water can infiltrate into the soil. During low tide, water can drain out of the monoliths. We will 
compare groundwater level changes in the monoliths to see whether the soil treatments affect 
drainage. Furthermore, we will also compare the biogeochemical functioning of the treatment soils 
by comparing the nutrient concentrations in the drainage water of each monolith with nutrient 
concentrations in the flooding water. 
 
Keywords: groundwater flow; tidal marsh restoration; biogeochemical cycling  


Improving groundwater dynamics: a key factor for successful tidal marsh restoration?

http://www.vliz.be/imisdocs/publications/311667.pdf

Improving groundwater dynamics: a key factor for successful tidal marsh restoration?

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