Effects of Cohesive Sediment on Estuarine Morphology in Laboratory Scale Experiments

L. Braat, J.R.F.W. Leuven, I.R. Lokhorst, M.G. Kleinhans

Research output: Contribution to conferenceAbstractOther research output

Abstract

Mud plays a major role in forming and filling of river estuaries. River estuaries are typically build of sand and flanked by mudflats, which affect channel-shoal dynamics on time scales of centuries to millennia. In our research we aim to study the effects of mud on the shape and evolution of estuaries and where the largest effects occur.
Recently a 20 m by 3 m flume (the Metronome) was developed at Utrecht University for tidal experiments. Complete estuaries are simulated in the Metronome by driving tidal flow by periodically tilting of the flume to counteract scaling problems. To simulate the effects of cohesive mud we supply nutshell grains to the system together with the river discharge. Three scenarios were tested, one with only sand, one with a low supply concentration of nutshell and one with a high concentration (left to right in figure).
Estuaries that developed from an initial convergent shape are self-formed through bank erosion, continuous channel-shoal migration and bar and mud flat sedimentation (figure shows development over 15000 tilting cycles). The cohesive sediment deposits occur mainly on bars, but also on the flanks of the estuary and in abandoned channels. Due to its different erosional and depositional characteristics, the nutshell increases the elevation of the bars, which reduces storage and ebb-dominance and causes reduction of bar mobility and short cuts. These results agree with numerical model results. The large-scale effect is less widening of the estuary in the presence of mud and a decrease in channel-shoal migration, suggesting that mud confines estuary width in a similar manner as river floodplains.
Original languageEnglish
Publication statusPublished - 11 Dec 2017
EventAGU Fall Meeting 2017 - New Orleans, United States
Duration: 11 Dec 201715 Dec 2017
https://fallmeeting.agu.org/2017/#

Conference

ConferenceAGU Fall Meeting 2017
Abbreviated titleAGU Fall Meeting 2017
Country/TerritoryUnited States
CityNew Orleans
Period11/12/1715/12/17
Internet address

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