Preprints
https://doi.org/10.5194/esurf-2021-75
https://doi.org/10.5194/esurf-2021-75

  10 Nov 2021

10 Nov 2021

Review status: this preprint is currently under review for the journal ESurf.

Estuarine morphodynamics and development modified by floodplain formation

Maarten G. Kleinhans1, Lonneke Roelofs1, Steven A. H. Weisscher1, Ivar R. Lokhorst1,2, and Lisanne Braat1,3 Maarten G. Kleinhans et al.
  • 1Department of Physical Geography, Utrecht University, Princetonlaan 8A, 3584 CB, Utrecht, The Netherlands
  • 2Nelen & Schuurmans, Zakkendragershof 34-44, 3511 AE, Utrecht, The Netherlands
  • 3European Space Agency (ESA), European Space Research and Technology Centre (ESTEC), Keplerlaan 1, 2201 AZ Noordwijk, The Netherlands

Abstract. Rivers and estuaries are flanked by floodplains built by mud and vegetation. Floodplains affect channel dynamics and the overall system's pattern through apparent cohesion in the channel banks and through filling of accommodation space and hydraulic resistance. For rivers, effects of mud, vegetation and the combination are thought to stabilise the banks and narrow the channel. However, the thinness of mudflats and salt marsh in estuaries compared to channel depth raises questions about the effects of floodplain as constraints on estuary dimensions. To test these effects, we created three estuaries in a tidal flume: one with mud, one with recruitment events of two live vegetation species and a control with neither. Both mud and vegetation reduced channel migration and bank erosion and stabilised channels and bars. Effects of vegetation include local flow velocity reduction and concentration of flow into the channels, while flow velocities remained higher over mudflats. On the other hand, the lower reach of the muddy estuary showed more reduced channel migration than the vegetated estuary. The main system-wide effect of mudflats and salt marsh is to reduce the tidal prism over time from upstream to downstream. The landward reach of the estuary narrows and fills progressively, particularly for the muddy estuary, which effectively shortens the tidally influenced reach and also reduces the tidal energy in the seaward reach and mouth area.

Maarten G. Kleinhans et al.

Status: open (until 23 Dec 2021)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on esurf-2021-75', William Kearney, 06 Dec 2021 reply

Maarten G. Kleinhans et al.

Data sets

Bathymetries of the three experiments Kleinhans, Roelofs, Weisscher, Lokhorst, Braat https://doi.org/10.24416/UU01-R3ZUC9

Maarten G. Kleinhans et al.

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Short summary
Floodplain formation in estuaries limit the ebb and flood flow, reducing channel migration, and shortening the tidally-influenced reach. Vegetation establishment on bars reduces local flow velocity and concentrates flow into channels, while mud flats fill accommodation space and reduce channel migration. These results are based on experimental estuaries in the Metronome facility supported by numerical flow modelling.