[Lonnie A]

units are 1000m2 or acre

To connect reach to storage area use the Edit->Move points/objects and drag the last point of the reach into the storage area. RAS will then ask if you want to connect it.

If you find stability issues once you get it connected:

You will likely need to set the initial conditions of the SA to be close to the elevation your channel WSE (without the connection) at the initial model start time.

You may find increasing you SA area a little can help with stability as well.

[Lonnie A]

The way I do this in a 1D/2D model is to have to 2D areas (left and right of channel) Along the channel they are connected to channel with laterals. Over the culvert the 2 2D areas are connected with storage area connector. The culvert (or lidded XS) high chord is set artificially high so no flow can go over the culvert deck and is forced into the 2D flow area. If you don’t set the deck high it will allow flow to calculated overland, over, and through the culvert. Setting it high keeps flow confined to 2d mesh and culvert.

[Lonnie A]

You might try tying the end of the reach into a storage area that has a small volume, then have that storage area tied to the dam with a connector.

[Lonnie A]

One “trick” I use is just to draw a zig-zagged breakline in the area I want smaller cells and then edit the breakline cell spacing to the resolution I’m looking for.

[Lonnie A]

If you select the 2D flow area with a single left click you should see a “remove all cell points outside perimeter” option. Selecting that will remove the points and having breaklines that run past the boundary shouldn’t be an problem.

[Lonnie A]

I use a tool by Aris called Grid & Raster Editor within GIS that allows you to edit the individual raster pixel elevations. If you google aris you should find it. Relatively inexpensive.
I can usually edit the terrain file mapper is using and have it reprocess the 2D flow area to get the cell elevation to update but there are times you have to recreate the terrain file for it to actually update the flow area. When that happens it is usually with models that have more than 1 2D flow area.

[Lonnie A]

I use a GIS addin tool from Aris that lets you edit raster cell elevations either one by one or as a group. Usually I can edit the tif made by mapper but sometimes RAS doesn’t acknowledge the edits even though I can see them in the terrain. When that happens I recreate the terrain from the edited surface. Works particularly well when you need to lower cells near culverts.

Here is a link to the tool. I’m not affiliated with them but it’s the simplest tool I’ve found. Interested to hear what others are using.
http://www.aris.nl/index.php?option=com_content&view=article&id=210:aris-grid-editor-for-arcmap&catid=64:arcgis-tools&Itemid=161&lang=en

[Lonnie A]

I’ll throw this out for consideration. I have a model that I’m modeling the channel in 1D and have it tied to a left and right overbank 2D area. Along the length of the channel are some long culverts. What I did was stitched the 2D area together over the culvert so that flow could leave the channel and flow in the 2D area and be able to spill between the 2D areas along the culvert. This was an existing model that I added 2D to so the culvert deck was already coded in.
When I made my first run I realized that I was getting a “double counting” of flow leaving the channel due to the 2D area taking flow and the 1D also accounting for weir flow over the culvert deck. I went back and raised the deck to an artificially high elevation so I could eliminate 1D accounting for weir flow the profile was closer to what the 1D only was showing for a headwater.

[Lonnie A]

In the flow editor window as the 2D flow area as a boundary and then assign precip to it. It will distribute the rainfall uniformly over the 2D mesh

[Lonnie A]

Did you set a initial stage in the 2D? Is it may be the volume is filling the 2D initially? With the warm up you are probably filling the 2D area ahead of the run which is why you are getting better results?

[Lonnie A]

You have to convert the tin to a raster prior to importing it into RAS. Not sure on the elevation issue. In the main window of RAS under options it isn’t set to metric by chance is it? I don’t believe that would be the cause, more likely a issue with the raster/projection.

[Lonnie A]

It is as you state due to the linear interpolation between U/S and D/S cross-sections. You might try moving your bounding cross-sections closer to the road which will reduce the elevation difference some.

The other thing you could look at is the continuity of flow. It looks like you have a lot of flow approaching and overtopping the road in the right overbank but on the downstream side the section has most of the flow back in the channel. You might need to adjust ineffective and/or n-values to try to force more flow to be in the right overbank on the downstream side. The difficulty you are having here is that more than likely the right overbank on the downstream side has a higher WSE than in the channel which you can’t model in a 1D model.

[Lonnie A]

In the picture below I would model as one reach. The island is small enough that the WSE left and right of it isn’t going to vary enough to worry about. Depending on the WSE upstream of the island can you see that flow has the ability to enter the area to the right of the island? If it doesn’t put ineffective flow in that area. You can also look at what the flow is computed to be in the right overbank of the XS just before the island and then look at what the flow is computed in the two section that cover the island to see if there is a relative continuity of flow and then play with ineffective station to get a relative agreement. For example if the U/S XS shows 2000 cfs in right overbank and the 2 next DS show 3000 cfs add ineffective in the right overbank to have a closer agreement on those 2 XS. You might need to adjust your bank station to be on the island and inline with it to figure out this continuity and then after a few iterations move the bank stations back to where they belong.

[Lonnie A]

It didn’t cut the area, it is showing the area filled. In the geometry editor select view at the top and then unclick the “fill in storage areas/2d flow areas”

[Lonnie A]

There isn’t in the current version. Hoping they add the ability to view connections in Mapper when V5.1 comes out.

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