# Why is there &quot;Roughness Options (legacy)&quot; and what does &quot;masks&quot; mean?

Two questions with the example “DM-02_Lake_Okeechobee_Example”:Question 1:As shown is Fig.1, why there is a “multiplicative factor = 0.005”? Does it means roughness in all cells should be multiplied by 0.005? In this way, the average value is “0.257*0.005=0.001285”? But in ViewPlan, the roughness has two values: 0 & 0.005? Does the original value is 0/0.005=0 & 0.005/0.005=1?Question 2:In Fig.2, there set some “masks (black lines)” in the lake. I understand that these masks are set to represent littoral area. Could you teach me how to correctly set these masks? They seem complex.Thanks!
Fig1.jpg
Fig2.jpg

The multiplicative factor you are looking at is a legacy option. This is provided for only users who are very familiar with EFDC and understand the code. Normally users will never need to make changes to the legacy items. Any changes to cell roughness should be made using the Assign button in the Bottom Roughness frame or from ViewPlan. https://eemodelingsystem.atlassian.net/wiki/spaces/EEREF/pages/2380313/Initial+Conditions+and+Bottom+Roughness+Tab Setting the masks is relatively straightforward when in the Grid tab here:https://eemodelingsystem.atlassian.net/wiki/spaces/EEREF/pages/2380317/Grid+TabOr from ViewPlan as shown here:https://eemodelingsystem.atlassian.net/wiki/spaces/EEREF/pages/2379989/Single+Cell+Edits or in this video from time = 18:03 Hydraulic Structure Controls in EFDC+ - YouTube

About Question 2, what I want to ask is not the process in EE interface (e.g., click which icon), instead, I want to know how you set a particular mask in a specific cell? For example, Figure 2 (Okeechobee Demo in EE website), why these particular grids have “masks”? And why they are “force U & V componet only” Is there a reason? If I have a lake where there are littoral zones like Okeechobee, how can I determine these masks? In Figure 2, I can see that the outline of these masks is the outline of the littoral zone, but how do you determine the tetails?

About Question 1: What are the “real” roughness values used in the model? Becasue the values are “0” or “1” in the “dxdy.inp” (Fig.3), However, in EE’s “Viewplan”, the values are “0” and “0.005” (Fig.4). Which one should I believe?

Could someone help me about question in 4th Post? I have been confused for several days.

I have a hypothesis about this “roughness value”, which I mentioned in 1st Post. Is the inconsistency between “.inp” and “ViewPlan” because of the “multiplicative factor = 0.005”? As you can see, values of roughness in “dxdy.inp” are “0” or “1”, values in “ViewPlan” are “0” or “0.005”. They have a “multiplicative factor” multiple. Is my opinion right? Through this “multiplicative factor = 0.005”, is the “real” vulue when calculating the model “0 & 0.005”?

By the way, should I refer to the model file established by Jeff Ji in his book and several published papers? The model file is avaliable in this website(Hydrodynamics and Water Quality: Modeling Rivers, Lakes, and Estuaries, 2nd Edition | Wiley). Have you checked this model in the above website? Is it correct or somewhere wrong? Look forward to your advice!

Sincere apologies for the delayed reply.In general, if you do a full write from EE, the value that is in the input files will match the values in dxdy.inp. Regarding the Lake Okeechobee model, we have been discussing several things about the model that you and others have raised on the forum. We will be revising the model to address some of those problems.If you find something that is confusing like this in a demonstration model, please continue to ask questions. Additionally, I would suggest checking some of the more current demonstration models. They are arranged in the website in chronological order. I would suggest checking out the Lake T demonstration model, which we frequently use for our training courses.Tom

The model we have on our website is a modified version of Jeff Ji’s model as I understand it. That model was developed many years ago now, so I don’t have any direct knowledge of what was done to it on our end. If Lake Okeechobee is something you are really focused on, you may consider just setting up your own model using one of our guidance documents and Jeff Ji’s model as a general template. In that way, you might answer a lot of your questions and help your understanding without having to worry about the legacy options. As I mentioned before we are looking at redoing that model with our current EEMS software, but you probably won’t want to wait on us to do that.In my experience, I’ve stayed away from all of the legacy options and instead just stuck to defining values directly using the EFDC_Explorer interfaces. I find the bottom roughness values of zero and one to be very odd, and it looks like you are correct in your assumption that the multiplier is what is defining what those values actually are. Whether or not a roughness value of zero is appropriate or not is a matter of opinion, and I would generally say it is not an appropriate value.

Just to be absolutely clear: I would strongly advise against using zero and one values in dxdy.inp with a roughness value multiplier as you are suggesting is the case with this model. As you’ve already seen that can result in a lot of confusion as to what the values actually are.

Sincere apologies for the delayed reply.In general, if you do a full write from EE, the value that is in the input files will match the values in dxdy.inp. Regarding the Lake Okeechobee model, we have been discussing several things about the model that you and others have raised on the forum. We will be revising the model to address some of those problems.If you find something that is confusing like this in a demonstration model, please continue to ask questions. Additionally, I would suggest checking some of the more current demonstration models. They are arranged in the website in chronological order. I would suggest checking out the Lake T demonstration model, which we frequently use for our training courses.Tom

The model we have on our website is a modified version of Jeff Ji’s model as I understand it. That model was developed many years ago now, so I don’t have any direct knowledge of what was done to it on our end. If Lake Okeechobee is something you are really focused on, you may consider just setting up your own model using one of our guidance documents and Jeff Ji’s model as a general template. In that way, you might answer a lot of your questions and help your understanding without having to worry about the legacy options. As I mentioned before we are looking at redoing that model with our current EEMS software, but you probably won’t want to wait on us to do that.In my experience, I’ve stayed away from all of the legacy options and instead just stuck to defining values directly using the EFDC_Explorer interfaces. I find the bottom roughness values of zero and one to be very odd, and it looks like you are correct in your assumption that the multiplier is what is defining what those values actually are. Whether or not a roughness value of zero is appropriate or not is a matter of opinion, and I would generally say it is not an appropriate value.

Just to be absolutely clear: I would strongly advise against using zero and one values in dxdy.inp with a roughness value multiplier as you are suggesting is the case with this model. As you’ve already seen that can result in a lot of confusion as to what the values actually are.