# Thread: 1D2D Modelling - inlet capacity of manholes

1. ## 1D2D Modelling - inlet capacity of manholes

I have a real storm water case study where the storm water cannot enter the minor sewer system and remain on the surface due to insufficient inlet capacity.
I am modelling it with ICM and the catchments are connected to the manholes thus the storm water goes directly to the minor system and only floods into the 2D overland mesh in case of sewer surcharge.
Is there any possibility for the runoff from the catchments remain on the 2D overland mesh if the inlet manhole do not have capacity?
I tried already all the manholes "Flood types" and believe that the catchments must be directly connected to the manholes and the alternative I have is to forget the catchments and apply the rainfall directly to the 2D mesh.
Any suggestion?

Thank you!

Rui Pina

2. This was response from the support@innovyze.com address direct to Rui:-

This is a kind of halfway house between the 1D subcatchment approach and the 2D Direct rainfall modelling approach and is something we are looking into.

There are 2 potential workarounds, one which uses dummy links to limit flow and the other which uses 2 sub-models:-

• Apply a subcatchment to a 2D Manhole and use a limiting discharge orifice link to limit how much flow can actually pass further into the system. Excess flow will be transferred to the 2D zone at the manhole.
• Run one simulation with the 1D Inlets and work out the inlet exceedance flow. You could then apply this flow to a 2D Point Source boundary.

3. In the end, I came with this solution: Modelling gullies with orifices that connect 2D nodes (considered virtual, just to make the connection) with manholes nodes of the 1D network.

Now I want to access the importance of cleaning gullies and build stochastic flood risk maps base on their cleaning condition. The general idea is to do various runs with different inlet capacities, which are modelled by changing orifices parameters (discharge coefficient and limiting discharge). To do this, I believe I have 2 options:

1. By creating several scenarios in ICM.
This might be the best way to do this, but the amount of runs I want to make would take me too long to set up the scenarios. Is there any way to automate this process? I don't know if Ruby scripts can do this or if there is other Infoworks product that can do it (ICM Exchange?). If Ruby scripts can do this, does anyone knows where can I find an example?

2. By doing a long term simulation with the orifice parameters changing in time and repeating the same rainfall event along the simulation.
This can be an option, but I would have problems with the initial conditions. For example, the same rainfall event can be repeated over several days in the simulation, and for each day I would have different orifice parameters. I would discuss the initial conditions problem afterwards. However, is there any possibility of changing orifice parameters over time, like SWMM has the rule control option?

These are my ideas for now, but any other suggestions are welcome!

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