Tidal marsh restoration design affects feedbacks between inundation and elevation change
Oosterlee, L.; Cox, T.J.S.; Vandenbruwaene, W.; Maris, T.; Temmerman, S.; Meire, P. (2018). Tidal marsh restoration design affects feedbacks between inundation and elevation change. Est. Coast. 41(3): 613-625. https://dx.doi.org/10.1007/s12237-017-0314-2
In: Estuaries and Coasts. Estuarine Research Federation: Port Republic, Md.. ISSN 1559-2723; e-ISSN 1559-2731, meer
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| Trefwoorden |
Marien/Kust; Brak water; Zoet water |
| Author keywords |
Tidal marsh restoration, Hydro-geomorphology, Biogeochemistry, Controlled reduced tide (CRT), Habitat creation, Adaptive management |
| Abstract |
Tidal marsh (re)creation on formerly embanked land is increasingly executed along estuaries and coasts in Europe and the USA, either by restoring complete or by reduced tidal exchange. Ecosystem functioning and services are largely affected by the hydro-geomorphologic development of these areas. For natural marshes, the latter is known to be steered by feedbacks between tidal inundation and sediment accretion, allowing marshes to reach and maintain an equilibrium elevation relative to the mean sea level. However, for marsh restoration sites, these feedbacks may be disturbed depending on the restoration design. This was investigated by comparing the inundation-elevation change feedbacks in a natural versus restoration site with reduced tidal exchange in the Scheldt estuary (Belgium). This study analyzes long-term (9 years) datasets on elevation change and tidal inundation properties to disentangle the different mechanisms behind this elevation-inundation feedback. Moreover, subsequent changes in sediment properties that may affect this feedback were explored. In the restoration area with reduced tidal exchange, we found a different elevation-inundation feedback than on natural marshes, which is a positive feedback on initially high sites (i.e., sediment accretion leads to increasing inundation, hence causing accelerating sediment accretion rates) and a gradual silting up of the whole area. Furthermore, there is evidence for the presence of a relict consolidated sediment layer. Consequently, shallow subsidence is less likely to occur. Although short-term ecological development of the tidal marsh was not impeded, long-term habitat development may be affected by the differences in hydro-geomorphological interactions. An increase of inundation frequency on the initially high sites may cause inhibition of habitat succession or even reversed succession. Over time, the climax state of the restoration area may be different compared to natural marshes. Moreover, sediment-related ecosystem services, such as nutrient and carbon burial, may be positively influenced because of continuing sedimentation, although flood water storage potential will decrease with increasing elevation. Depending on the restoration goals, ecosystem trajectories and delivery of ecosystem services can be controlled by adaptive management of the tidal volume entering the restoration area. |
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