modeling surface drainage runoff

Hello Hossam,

Which Bentley product are you using?

By "gravity free surface drainage runoff", do you mean rainwater runoff from a catchment/drainage area? If so, you could model this using the catchment element connected to a catchbasin (and storm event configured) in StormCAD, CivilStorm or SewerGEMS. The catchbasin can be configured to use a standard inlet such as a curb, grate or slot. Standard HEC-22 inlet calculations are used to calculate depth and spread in the gutter.

If you are interested in the depth and spread in a gutter before (upstream of) any collection point/inlet, you can still look at the depth and spread reported at the catchbasin inlet location if it is set as on-grade (with the runoff modeled as a catchment connected directly to a catchbasin node), as the depth and spread is located at the upstream side of the inlet location, where the spread and depth will tend to be highest (before some of the approach flow is captured - see this article).

In the StormCAD product (of the GVF-Rational solver in CivilStorm or SewerGEMS), you can use the automated design feature and the program will select from a list of available inlet sizes necessary to meet a certain depth or spread constraint (depending on whether the inlet is on grade or in sag - see this article)

If you are new to StormCAD (GVF-rational solver in CivilStorm or SewerGEMS), you can find fundamentals training on our YouTube channel here.

If this does not help, please explain more about what you need to do.

Hi Jesse,

Yes, rainwater runoff, i am calculating surface runoff, without using using any positive system( Catch basins, piping) depending only on road side and longitudinal slope. i am using sewerGEMS, i need to simulate the road cross section and calculate the the depth of gutter and spread of water to check is it will exceed the curb limit or not. 

Hossam Hamed said:

without using using any positive system( Catch basins, piping) depending only on road side and longitudinal slope.

By this, do you mean that you do not want to model any sub-surface piping, and that you do not have any inlets, but rather just a series of gutters that act as channels? If so, you can still model this, but you'll have to use catchbasin elements to model the points where you want to view the depth and spread. You could set the inlets as % capture with a near-zero capture percentage (so that no flow is captured) as mentioned in this article. You can just model the catchbasins and connecting gutter link elements, without needing the sub-surface conduits, as explained in this article.

Alternatively you can model this using a series of cross sections and channels, with the cross section configured to model the cross sectional shape of the gutter/road at each point that you want to measure it. You could then manually check the calculated depth and Flow-Width result fields at the cross section locations.

Hi Jesse,

I tried second alternative, it works well and give me the proper answer for what i was looking for.

Many thanks. 

Dear Jesse,

unfortunately, the model example in the link you provided does not match the screenshot and the model has no outfall with many user notifications. would you please revisit your wiki post "Analyzing surface gutter and inlet capture without subsurface conduits"

Thanks,

Hello Mohamad,

The example model is not intended to perfectly match the screenshot in the article - it was added after the original posting of the article and is intended as a supplement. The outfall was omitted intentionally, to demonstrate how a model can still be computed, with only on-grade and in-sag inlets. The downstream inlet is in-sag and collects 100% of the approach flow.

The warning messages in the example model are mostly expected. For the ones that talk about flow being lost due to on-grade inlets with no subsurface conduits, these are expected because the example is only analyzing the surface network, and is ignoring what happens when some of the runoff is captured by the inlet and enters the subsurface network. 

The purpose of the article and example model is to explain how the user can analyze surface drainage only, without needing to add subsurface conduits and outfalls. This is useful in cases where you are wanting to design the surface gutter network first and do not want to look at the subsurface piping yet.

With that being said, I have amended the article and the example model for clarity.

Hello Mohamad,

The example model is not intended to perfectly match the screenshot in the article - it was added after the original posting of the article and is intended as a supplement. The outfall was omitted intentionally, to demonstrate how a model can still be computed, with only on-grade and in-sag inlets. The downstream inlet is in-sag and collects 100% of the approach flow.

The warning messages in the example model are mostly expected. For the ones that talk about flow being lost due to on-grade inlets with no subsurface conduits, these are expected because the example is only analyzing the surface network, and is ignoring what happens when some of the runoff is captured by the inlet and enters the subsurface network. 

The purpose of the article and example model is to explain how the user can analyze surface drainage only, without needing to add subsurface conduits and outfalls. This is useful in cases where you are wanting to design the surface gutter network first and do not want to look at the subsurface piping yet.

With that being said, I have amended the article and the example model for clarity.