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Ken_Li

24/08/2016 08:30:16

Hi all

I am a uni student and am doing my final year project. I am new to this model and I somehow got lost. To run the simulation, I need to have a QTBDY, at least two river cross sections and a HTBDY, is it the case? The problem is that I have produced the river cross section by using Lidar and the EA river shape file, it comes out as many lines which is fine. However in order to run the simulation, I will need to manually add the river section nodes and input the cross section data(x,y,easting and northings) again....is there any faster and logic way to sort this out? Thanks so much!!

 

 

 

Bob

Flood Modeller Support

25/08/2016 11:23:48

Hi

Please can you tell me what format your cross section data are currently in? It sounds like you started from a LiDAR grid - one thing to note with these data is that it may not include the bathymetry of the main river channel as if this is "wet" the LiDAR won't have a reading.

If your data is in a grid format (ASCII or binary flt) then you can draw lines to represent cross sections (the cross section generator tool can do this automatically if you have a river centreline polyline shapefile). There are tools to extract the underlying ground level data for each line (from the grid dataset) and write these data to a Flood Modeller 1D network format.

Note you will probably have to carry out further editing of section properties to specify things like roughness (you can use global edit tools for this), distance to next section (there is a tool for this) or panel markers (and a tool for this also).

With a very basic model, like you describe, it may be just as easy to draw individual sections across your grid, using Map Tools > Plot section and then export these data to csv format. These can then be copied and pasted into new river section units manually.

Hope this helps.

Regards

Bob

 

danielcb12

13/12/2018 09:58:09

Hi, 

I am in a similar situation where I am doing my final year project and I am modelling the effect of Large Wood in a stream in a rather steep valley. I have had issues with sub-critical flow caused by the gradient and I am trying to get around it by using as many x-sections as I can to minimise the change in slope.

I am also using Lidar for my ground values (1m resolution) and I originally just manually edited about 40 x-sections to add the channel in, as this wasn't detectable by lidar. Now that I have around 200 x-sections this is not practical. Is there a way to edit all x-sections in one go to add a standard small channel to them. For example; 3 measurements around x=0 that are 0.3 m less than the elevation values? 

I hope this makes sense and I look forward to your reply. 

Regards

Dan 

Bob

Flood Modeller Support

13/12/2018 16:26:06

Hi Dan

I'm afraid there is no tool currently available within Flood Modeller to make the changes you require. If you're working through 200 sections then you might find it easier to utilise the fact that the network (.dat) file can be viewed in a text editor. You could add the x-y data for your 3 extra rows hopefully quicker there (not worrying about the coordinate data). Then when you bring the revised network into the Flood Modeller interface you can use the "Fill in missing Easting and Northings" tool to update the coordinates for your new section points.

Don't forget though if you're adding extra section points in this way then you'll also need to update the number of points value for each section (parameter located immediately above list of points in each section when looking in text editor).

An alternative option to the above could be to discard some of your 200 sections, change the remaining ones (e.g. say 20 equally spaced along the reach) and then recreate the in-between sections using "interpolate" units. It depends on the shape of your channel as to whether this option is viable, but if it is it would mean a lot less manual editing.

Hope this provides some useful information.

Regards

Bob

danielcb12

14/12/2018 12:52:53

Hi Bob, 

Thanks for the reply, I hadn't thought of editing in a txt file so that was really useful! The model now seems to be working with your latter suggestion of using interpolated units! 

My intention is to model the effects of large wood with respect to peak flows and lag times. I am simulating LW my increasing the mannings number to 0.22. I have tested this by adding it to one section at a time and compared the results. I have compared the results by creating a time series on my final x-section and extracting the data but they all seem to be the same regardless of how many "LW" structures I put in. Should I be taking the flow data another way?

Thanks 

Dan 

Bob

Flood Modeller Support

17/12/2018 10:07:54

Hi Dan

Changing the roughness sounds like an acceptable method for what you're trying to simulate. And changing the roughness that much you'd expect to see some lag in the outflow. So it could be you need to change more sections, or more points on each section, to have an effect (what if you go to an extreme and change more sections and to an even higher roughness - just to see what effect you can have on outflows).

An alternative option could be to introduce some low weirs to represent obstructions in the flow.

Hope this helps

Regards

Bob

 

danielcb12

17/12/2018 10:10:57

Hi Bob, 

Thanks for your reply. I increased the roughness and there is now a clear difference betweeen no LW and a reach complete with LW. 

Kind regards

Dan

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