How to make a "small" channel for water to flow in lake's shallow littoral zone

This question is about demonstration model about Lake Okeechobee on the website (DM-02 Lake Okeechobee Temp-Dye – EE Modeling System). When I define the boundary conditions (flow into/from), I am confused about this question below: Take C41H78 or S129 as an example (Fig.1, or refer to SFWMD’s website: ArcGIS Web Application), I want to make them the flow boundaries in the model. You can see that their locations are near the shallow littoral zone (marsh), and from the map there are small but deep channels (look like man-made. I don’t know weather they’re concrete) (red box in Fig.1) to make water flowing into the deeper areas of Lake Okee. I would like to ask that how can we model these “small channel” in the marsh? I think its difficult because (1)the bottom elevation of “small channel” is low while the zone near it is high (Fig.2);(2)the channel is narrow compared to the cell size, so to create this channel we must first refine the cells a lot, slowing the model a lot. Could you tell me how to model this “imaginary” “small” channel? Or maybe is it unnecessary for modeling such channels? Because in the demo model, I do not find these handlings. But I am worried if the circulation will be affected or flows cannot flow into the lake because of high elevation in the littoral zone? I say “imaginary” is not because it is nonexistent, but because these channels’ elevation observation data is not provided in bathymetry measurement. As a result, they are not reflected in the littoral zone in the model.

In general, the kinds of features you are talking about are not something that can be addressed at the scale of a large lake like Lake Okeechobee. This is because the dynamics in and around this small channel are occurring at a much smaller scale than this model is intended to capture. If you are interested in these small-scale features you would need to create a model with a much finer grid resolution, which would result in the rest of the model running much more slowly.