Modelling retarding basins

[daveM85]

Hi there,

I’m new to RORB and I’m currently testing a model for post-developed conditions with the introduction of a retarding basin. I have worked out the elevation-storage relationship based on a preliminary design of the wetland.

I would like to confirm the different steps in the process of obtaining the right outflow and sizing of the outfall from the retarding basin:
1. For each duration, identify the critical storm as per ARR2016;
2. For each critical duration, change the number and size of the outfall pipes to maintain the desired outflow (pre-developed conditions) and maximise the volume of storage without using the spillway (all the flow in the pipe/s);

Is the above correct or are there are other considerations?

Thanks for your help.

[Benson Liu]

Hi Dave,

In general your approach seems fine but there may be site specific details that could change how you would approach this. Without looking at it in detail it would be difficult to give you more advice.

Kind regards,

Benson

[daveM85]

Thanks Benson.

I have attached the parameter and geometry files of the RORB model along with the input files used.

For example, looking at the storage RB4(MW)/RBWL9(DPM), using the ensemble method, the critical storm is identified by a duration of 30 minutes and TP25, with Q100=9.668 m3/s.

Therefore, I use the same TP and critical duration and change the pipe size/slope in order to ensure that no spillway flow from the retention basin and obtained an outflow from the storage of 0.703 m3/s with no.2 x 900dia pipes and 0.56% slope. Is this the right process for the determination of the most efficient outfall?

Thanks again for your help!

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[daveM85]

Hi Benson,

It looks there was a problem with the previous attachment, I’ve tried to attach a zip file, hopefully it will work.

Attachments:

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[Benson Liu]

Hi Dave,

How you optimise the pipes to ensure the goals are met is a decision the user needs to make, there are many project specific details that may influence the process. You may need to consider other factors such as attenuation and volume of storage when designing a retarding basin. As this is not a RORB specific question and more of best engineering practice the process of designing a retarding basin will need to be chosen by the user.

Kind regards,

Benson

[roloko3965]

http://elcomericio.me/

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