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. 
 

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

 

 

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Query regarding morphological modeling

NS
Neeraj Singh, modified 5 Years ago.

Query regarding morphological modeling

Youngling Posts: 3 Join Date: 10/31/14 Recent Posts
Hello everyone,

I am trying to estimate the rate of siltation (per annum) in Mumbai harbour region and in its main navigation channel. The harbour is dominated by tidal filling and emptying process which results in strong tidal currents, and is naturally sheltered from wave action, which is why I am not modeling waves. I have some basic doubts which I would like to enlist:

1. I want to create a morphological tide which will produce the same residual transport and morphological change patterns as that of a full year astronomic tide. I referred to the literature [Latteux (1995), Lesser (2009), Grunnet (2004), and Gelfenbaum et al (2002)] to get some idea, but still a few things are not clear to me. I understood that the spring-neap tidal cycle can be reduced to a single daily tidal signal which is usually 7%-20% larger that the full astronomic tide, and that I need to play with the amplitude and phase of the tidal constituents. But what should be the duration of that final morphological tide that I'll get? Also, do I need to run the model for an entire year using this morphological tide? Basically we are trying to reduce the inputs in order to reduce the computational time, so what is the use of reducing the input if I still have to run the model for a year? Do I need to analyse the whole year tide data and categorize it into different classes based on tidal range and its frequency of occurrence in a year? I know I am missing out on something really simple. Kindly comment on the duration of the reduced morphological tide, and the advantage of this particular input reduction technique.

2. In order to bridge the gap between the time scales of hydrodynamic and morphological processes, I wish to use MORFAC. I am rather confused with application of MORFAC in my case. I need to calculate the rate of siltation in meters per year, and also estimate the volume of sedimentation (in million cubic meters) per annum. A MORFAC value of, for example, 50, would mean that if the simulation time of my hydrodynamic model is 1 day, then I'll get the bed level change that would occur after 50 days? Am I correct? So if I need to calculate the bed level change after one year, then can I simulate the hydrodynamic processes for one month and just use a MORFAC value of 100 in order to obtain the bed level change that would occur after a year (30 days X 100 = 300 days)?

I am really confused about how to implement this ideal combination of morphological tide and morphological acceleration technique for my particular case. Kindly correct my wrong notions about both these techniques and help me to proceed further.

Thank you very much for your valuable time.

Have a good day

Neeraj Singh
M.Sc, Ocean Engineering
IIT Bombay