intro story Coast / Estuary

Coast / Estuary

Coastal systems are among the most dynamic physical systems on earth and are subject to a large variety of forces. The morphodynamic changes occurring to coastlines worldwide are of great interest and importance. These changes occur as a result of the erosion of sediments, its subsequent transport as bed load or suspended load, and eventual deposition. 
 
Estuaries are partly enclosed water bodies that have an open connection to the coast. Estuaries generally have one or more branching channels, intertidal mudflats and/or salt marshes. Intertidal areas are of high ecological importance and trap sediments (sands, silts, clays and organic matter).
Within the Delft3D modelling package a large variation of coastal and estuarine physical and chemical processes can be simulated. These include waves, tidal propagation, wind- or wave-induced water level setup, flow induced by salinity or temperature gradients, sand and mud transport, water quality and changing bathymetry (morphology). Delft3D can also be used operationally e.g. storm, surge and algal bloom forecasting. 
 
On this discussion page you can post questions, research discussions or just share your experience about modelling coastal and/or estuarine systems with Delft3D FM. 
 

** PLEASE TAG YOUR POST! **

 

 

Sub groups
D-Flow Flexible Mesh
DELWAQ
Cohesive sediments & muddy systems

 

 

Message Boards

A-priori determation of reasonable values of Sus,Bed,SusW and BedW?

Ben Williams, modified 8 Years ago.

A-priori determation of reasonable values of Sus,Bed,SusW and BedW?

Jedi Knight Posts: 114 Join Date: 3/23/11 Recent Posts
Hi all,

I am re-posting this question from a previous thread, as I am curious as to what other Delft3D users have found.

Essentially I am curious as to how to work out reasonable values of the 'calibration parameters' Sus, Bed, SusW and BedW in the morphology file. These variables correspond to contributions for total suspended load, total bed load, suspended load due to waves and bed load due to waves. These are calculated independently in the TRANSPOR2004 algorithm.

The default values for each of these are 1, which in reasonably deep water areas, or areas of highish current flow, seem to be OK. However in shallow water these values do not appear to be reasonable - in particular the value SusW seems to have a very significant effect on the overall sediment transport pathway in the surf zone.

There are several papers/ reports out there that look at 'calibrating' SusW and BedW for a particular locality, using eitehr a sensitivty analysis or OpenDA to obtain 'reasonable' estimates. However for a lot of engineering cases one does not have any kind of data to calibrate sediment transport rates and directions - you just know that something is a bit suspect when the vectors are not heading in the direction you would expect (e.g. offshore instead of alongshore/onshore, if you are hoping to get onshore accretion in some areas).

I recognize the limitations of using a depth-average model for sediment transport in the nearshore- however I am sure that Delft3D is commonly used for situations like this to look at e.g. accretion and erosion around a groyne or a jetty structure of some sort.

May I ask what kinds of values of Sus, Bed, SusW and BedW other Delft3D users have found to give vaguely realistic transport vectors in the nearshore? I have already had one estimate of SusW = 0.25 as a rough starting place.

I am aware of what these scaling parameters do and how they work, but surely there must be some way of avoiding a very tedious calibration / sensitivity exercise every time one wishes to simulate sediment transport.

Kind regards,

Ben

Useful references:

Van RIjn et al. (2007): Unified view of sediment transport by currents and waves. IV: Application of a morphodynamic model.

Walstra et al (2007). Effects of bed slope and wave skewness on sediemnt transport and morphology. Coastal Sediments 2007.

Briere et al (2010): Morphological modelling of bar dynamics with Delft3D: The quest for optimal free parameter setting using a an automatic calibration parameter technique. ICCE 2010. http://journals.tdl.org/ICCE/article/viewDownloadInterstitial/1237/pdf_258

Grunnet et al (2004) Process-based modelling of a shoreface nourishment. Coastal Engineering 51, pp 581-607 (http://www.sciencedirect.com/science/article/pii/S0378383904000729#)

Deltares (2008) report Z4479, Monitoring and modelling of a shoreface nourishment

Deltares (2004) report Z3748.21, Shoreface nourishment scenarios.

ftp://ftp.dep.state.fl.us/pub/ENV-PRMT/bma/2_Palm%20Beach%20County/Coastal%20Engineering%20and%20Planning%20Documents/200706_Final%20town%20of%20Palm%20Beach%20Erosion%20Control%20study/Appendix%20A%20-%20Delft3D%20Model%20Calibration%20Report.pdf