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

 

 

Message Boards

No model gradient, water won't flow downstream.

JS
Jamie Stackpole, modified 2 Months ago.

No model gradient, water won't flow downstream.

Youngling Posts: 6 Join Date: 7/25/19 Recent Posts
Hi all,
Having problems with model gradient. At the moment my model/bathymetry has diversity in elevation but water won't run from point A to B because there is no gradient to flow down. I currently have a total discharge boundary at the top and a Neumann boundary at the bottom (I figured the Neumann would provide gradient) however when I introduce water flow to the model the water stagnates and flows back out at the top boundary. Have I missed something that would otherwise provide a gradient to the model? I haven't attached the data yet but am happy to provide as necessary.Thanks for your help!
Dmitry Kushnir, modified 2 Months ago.

RE: No model gradient, water won't flow downstream.

Jedi Knight Posts: 103 Join Date: 11/9/12 Recent Posts
Hi Jamie,
I could have a look at your case if you upload some simplified version of your model data.
Regards,
Dmitry
JS
Jamie Stackpole, modified 2 Months ago.

RE: No model gradient, water won't flow downstream.

Youngling Posts: 6 Join Date: 7/25/19 Recent Posts
Hi Dmitry, I've attached some screen-grabs of where I'm at as I wasn't 100% sure what data you were looking for. What else can I upload to help?
At the moment I have water in my initial conditions file (A) with water at the top of the river. When the model is run, this water from the ini. file moves down the channel but additional water does not enter from the top boundary (B (image at mid-stamp). The boundary conditions are as a Total Discharge - Time-Series at the top and a Neumann - Time-Series at the bottom (C). If there is any other information needed please let me know!
It seems, from the what I understand, that either the boundary condition isn't introducing water to the model OR the 'wet' cells from the initial file aren't connecting with the Total Discharge boundary at the top.Thanks for your time!
Dmitry Kushnir, modified 2 Months ago.

RE: No model gradient, water won't flow downstream.

Jedi Knight Posts: 103 Join Date: 11/9/12 Recent Posts
Hi  Jamie,
I can barely see what is presented on the screen-shots. They seem to be uploaded in the very low resolution. From this data, it is difficult to judge what went wrong with the model.
Try to check you grid administration first. The common issue with the Total Discharge boundary conditions is that they depend on the grid cells numbering. See this thread for the details.
Regards,
Dmitry
FJ
Fremont Johnson, modified 2 Months ago.

RE: No model gradient, water won't flow downstream.

Youngling Posts: 1 Join Date: 4/17/20 Recent Posts
The water to flow faster which increases erosion and transport, which then reduces the gradient Lowes Life.
JS
Jamie Stackpole, modified 2 Months ago.

RE: No model gradient, water won't flow downstream.

Youngling Posts: 6 Join Date: 7/25/19 Recent Posts
PROBLEM SOLVED: Was a scaling error where the model had become so small that the grid gradient was so flat and water would stagnate rather than flow.