Low impact Development to model a green roof

Hello Abubakar,

The surface slope is at 10%, which seems pretty steep. You may want to try a different value to see if there is any impact. The Drainage Mat Manning's n is a pretty high value as well. Maybe test a slightly smaller value to see if there is any improvement.

There is a sample model found at C:\Program Files (x86)\SewerGEMS\Samples\Office Project that includes LID and green roofs as an example. This can be used as guidance for some values. If you are using CivilStorm, the same file can be found in the CivilStorm folder. More general information on LID can be found here: Low Impact Development (LID).

If this doesn't help, it would be useful to see a copy of the model files.

Regards,

Scott

Hi Scott,

thanks for the replay the sample file in the sewerGems they run as Bio-Retention cell, not a green roof I also lowed the sloop and the drainage mat Manning's but I am still running in the same problem/ 

Best Regards,

Abubakar, what values did you enter? Can you please share a copy of the model so we can test on our end?

Sharing Hydraulic Model Files on the OpenFlows Forum

Gulph Humber(Final year Project).zip

Hey Jesse, Did you get it?

Yes, we received the file. Someone will investigate and get back to you shortly.

Abubakar Hussein said:

I was able to run it with no issues but when I look at the results infiltration total is 0.0 do you know why is that?

Since you have set the green roof to occupy the full catchment, this means that rainfall cannot become infiltration - rather, it either becomes runoff, is stored inside the LID or exits via an underdrain or drainage mat. Meaning, the "infiltration" result is not applicable in this case. A green roof is often used in places where infiltration into the ground is not possible, so the green roof essentially soaks up a portion of the water.

I have added a note about this to the Low Impact Development wiki article

As a side note, I noticed the values you have entered for the surface storage depth, soil thickness and suction head are quite small (less than 1 mm) Perhaps a units issue with meters vs. millimeters?

Abubakar Hussein said:

I was able to run it with no issues but when I look at the results infiltration total is 0.0 do you know why is that?

Since you have set the green roof to occupy the full catchment, this means that rainfall cannot become infiltration - rather, it either becomes runoff, is stored inside the LID or exits via an underdrain or drainage mat. Meaning, the "infiltration" result is not applicable in this case. A green roof is often used in places where infiltration into the ground is not possible, so the green roof essentially soaks up a portion of the water.

I have added a note about this to the Low Impact Development wiki article

As a side note, I noticed the values you have entered for the surface storage depth, soil thickness and suction head are quite small (less than 1 mm) Perhaps a units issue with meters vs. millimeters?