[Lonnie A]

I’ve found profiles in RAS Mapper won’t report flows correctly if there is an internal connector structure within the sampled cell faces. For flow over the weir, get the results from within the geometry editor or look in mapper but a cell or two away from the structure.

[Lonnie A]

Export the max WSE raster then use that in GIS to create the contours from.

[Lonnie A]

It sounds like a issue with the model and not the software. Are you sure you are referencing the 2D areas correctly as HW and TW? Are the cells it is noting perhaps in the area you consider to be TW and not the HW? Regardless the weir elevations has to be higher than the connecting cells of both 2D areas.

[Lonnie A]

sounds like your river reach maybe drawn backwards. Reaches are drawn upstream to downstream. If you go under GIS tools and select reach invert line table there is a “reverse order” button

[Lonnie A]

You probably want to model that reach with mod puls. For quick reference Chris has a write up on it.
http://hecrasmodel.blogspot.com/2009/07/new-features-401-part-3modified-puls.html

[Lonnie A]

Under tools in RASMapper, Render Mode Options you can set a minimum depth to plot.

[Lonnie A]

Using the lidded XS option might do what you are looking for. In the cross section data window, under options, add a lid…

[Lonnie A]

That is just what you’ll get with the mapping for the way RAS is handling 2D. The volume going over the crest isn’t enough to fill the cells on the downstream side to show flooding of the whole street. The flow going over the road flows out of the cells on the downstream side at a shallow depth. Remember RAS is basically doing interconnected storage cells. What you are seeing is something like this.

[Lonnie A]

I think you are seeing the impact of the hybrid render mode. If you want to see the true model computed WSE you need to select the horizontal render mode (under tools in mapper). With the other ones you get mapping that interpolates from the computed WSE and can be misleading. Also note that there is a bug and when you create a static map it only outputs the hybrid render regardless of what was selected.

[Lonnie A]

It is hard to state which is best not knowing what the overbank looks like. If you think the area with the buildings is going to be just storage and no velocity in floodplain then ineffective would be a good choice. If there are a lot of buildings, enough that you would have difficulty capturing their effect, and you feel there would be velocity in the floodplain I would go with a higher n-values to reflect impact. Now if just a few buildings I would use blocked obstruction. The blocked obstruction will add wetted perimeter for the walls and potentially be more accurate.

[Lonnie A]

You would have to do the lake as a separate 2D area and connect to the surrounding 2D area with a storage area connector for what you are asking. I assume you are trying to apply a hydrograph to the lake is why you need a separate 2D area vs modeling the whole thing in one 2D area.

[Lonnie A]

As Cameron stated. You would have to do the routing outside of steady state, say in HMS or unsteady RAS.

[Lonnie A]

A “cheat” is to draw a storage area that covers your geometry and then go into mapper, right click on the storage area layer and export to shapefile. Now you have a shapefile that you can import as a landcover. This will let you use the regions tool. You can draw multiple SA for differing land classes if you wish.

[Lonnie A]

I’ve helped a colleague who was having the same issue. I couldn’t find any issue with the model but noticed that their terrain surface has a odd cell resolution of something like 6.562 so I resampled to a 5×5 and ran the model against that surface and it worked fine.

Even if your surface doesn’t have a odd cell resolution you might try resampling it to see if that clears it up. Most likely it is terrain related I’m betting.

[Lonnie A]

Aileen,

I would have to see the model to determine if there is something wrong with the model and advise on potential changes. You are running this in unsteady correct? Changing volume should of had a impact in unsteady but wouldn’t have if ran in steady.

your model schematic doesn’t look very large so you should be able to upload it here or if you want email it to me.

Lonnie

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