Irregular Shaped Obstructions

[Bridge]

I am trying to model the impact of an elevated walkway within a river and floodplain system. The walkway is about 5m-8m wide with a 450mm thick deck and 1.3m x 0.1m high handrails to each side. The walkway is supported on either single or double circular piers. The walkway is offset from, but is aligned parallel to, the adjacent river.

The local catchment authority (CMA) has agreed that obstructions can be used instead of trying to model an inline bridge structure. This approach is OK for the piers where I can use the Multiple Obstructions option. However, some parts of the walkway will become either partially or fully submerged in the 100yr storm event (yes, allowed). How do I model the irregular shape of the walkway as an obstruction?

The only thing I can think of is to work out the total cross-section area of the walkway below the flood level, and thicken the pier width to match?

Any advice much appreciated.

Cheers
Bridge

[cameron]

I would either switch to a bridge or add additional losses to the cross-sections where there is submergence happening.

[Anonymous]

Thanks Cameron,

Being a basic user, what do you mean by adding additional losses? Is this simply increasing the mannings n at the obstruction location? If so, how do you determine what the value for n would be?

If not mannings n, can you please advise what sort of loses you mean, and how are they modelled

Cheers

[cameron]

You could do Mannng’s or Minor Losses (in the table pull down menu). Knowing the correct value to use is the tricky part as you would want to calibrate it to something if possible.

[Lonnie A]

Using the lidded XS option might do what you are looking for. In the cross section data window, under options, add a lid…

[Anonymous]

I have a similar question. I have an elevated walkway runs parallel to a river. I wanted to know what the best way to model it is? 1)Modelling it as obstructions or 2)Manipulating the cross sections and embed the new piers and walkway in the cross sections or 3)Model it as an in-line bridge?

If I want to model it as in-line bridge, how can I do it? My walkway is more than 100 m long and contains several XS. Unfortunately, there is no similar example provided by HEC.

Thank you

[Author]

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