Utilizing ADCIRC fort.19 Files with SMS

Are your ADCIRC simulations producing unexpected results? Do tides behave oddly or bottom friction seem off? When simulations fall short of real-world behavior, the issue often lies in how input data is defined—especially the optional but highly influential fort.19 file.

Whether you’re refining tidal boundaries or spatial friction properties, learning how to properly use fort.19 in can elevate your modeling from approximate to accurate. The Surface-water Modeling System (SMS) simplifies using the fort.19 with your ADCIRC project. 

What Is a fort.19 File?

The fort.19 file in ADCIRC provides two powerful capabilities:

1. Time varying water surface elevations at boundary nodes

1. Used to simulate dynamic tides or river inflows

2. Must be consistent with the mesh’s open boundary node count and order

3. Values are linearly interpolated over time

2. Spatially varying Manning’s n values

1. Applies localized bottom friction across the mesh

2. Useful for models with mixed terrain types or vegetation

A single ADCIRC simulation can only interpret the fort.19 file in one way: as either time-varying boundary elevations or time-varying spatially-distributed bottom friction, depending on the configuration used.

Why Use a fort.19 File in SMS?

SMS simplifies ADCIRC setup with a visual interface, but SMS does not create fort.19 files automatically. Instead, it provides tools to:

• Assign boundary arcs

• Link your external fort.19 file

• Ensure alignment with the mesh

With the correct setup, SMS exports the file along with other ADCIRC inputs, readying it for simulation.

How to Use a Preexisting fort.19 File in SMS

If you’ve already created a fort file, follow these steps to incorporate it into your simulation:

1. Assign Boundary Conditions:

1. Use the Select Feature Arc tool to highlight the appropriate arcs (edges) of your mesh.

2. Right-click on the selected arcs, select Assign BC…, and select the correct Linear boundary condition options option for your model.

2. Link the fort.19 File:

1. Right-click on the “Boundary Conditions” coverage and select Forcing Options… 

2. Turn off the Tidal Forcing default option, then browse to and attach your fort.19 file.

3. SMS will validate that the number and order of nodes in your file match the boundary structure.

Can SMS Create a fort.19 File?

No, not directly. However, there are a few ways to generate your own fort.19 file:

1. Manually Identify Boundary Nodes

1. In SMS, select the open boundary arc(s)

2. Extract the node numbers and their order (e.g., via scripting or by exporting node data)

2. Generate Time Series

1. Use tools like MATLAB, Python, Excel, or a text editor to define tidal elevation values for each node

2. Format the data according to fort.19 structure: time in seconds, elevation in meters

3. Write to File

1. Save your data in ASCII format following ADCIRC’s required structure for fort.19

Currently, most users either manually create a fort.19 file or use one from a reliable source and link it through SMS.

Final Tips for Using fort.19 Successfully

• Node Matching is Crucial: Your fort.19 file must exactly match the node numbers and order along the open boundary arc.

• Don’t Confuse with fort.13: Use fort.13 for parameters like bottom roughness, not time-varying water surface elevations.

• Keep Time Alignment Clean: Timestamps in fort.19 should align with the simulation’s time step and output settings.

• Avoid Geometry Errors: Ensure there are no gaps, overlaps, or misaligned arcs in your boundary coverage.

• Validate Early: Run a model check in SMS before exporting to catch configuration errors.

Whether you’re simulating storm surge, tidal forcing, or river inflow, the fort.19 file gives you detailed control over boundary behavior and surface conditions in ADCIRC. SMS simplifies input management for the fort.19 file, enhancing ADCIRC's use as a site-specific decision-support tool when set up and validated carefully.

Try out using the fort.19 and other ADCIRC capabilities in SMS today!