Floating Obstructions

[Anonymous]

Hello,

I’m modeling a fairly simple stream and floodplain area. Easily defined channel, floodplains, and valley walls. I have a building fairly close to the channel, probably… <50 feet from the Top of Bank. Considering flows and elevations at the cross section, I initially set up my channel sections to end abruptly at the face of the building, and then go vertically to match the high elevation on the opposite bank that I ended my sections at.

So for example, at Station 0 on my cross section, I have two entries, one at elevation 1140 and the next at elevation 1114. Simple 1D modeling. Quick and dirty.

I'm beginning to tweak and fine tune my model now, and I wanted to extend my sections through the building and plop in an obstruction to identify the location of the building on each section. However, when I do that, the obstruction doesn't show to line up along the ground line of the section. The bottom point of the obstruction will either be above or below the interpolated ground line between two given points.

What am I missing? What went wrong? The graphical drawing of the obstruction doesn't appear to affect my results, but it's not super apparent either. Let me know if you can think of what's going on. Thank you!

HEC-RAS v5.0.1
1D Modeling

[NDiGennaro]

I figured it out!

I put the stationing in backwards. I was thinking left bank obstruction, and to block out an entire left overbank the “starting” station is the one closest to the channel. But when you only want a partial block, the starting station becomes the lesser stationing value.

Correct Example:

Normal Obstruction Mode:
Left Station = 240

Multiple Blocks Mode:
Start Station = 100
End Station = 240

I kept thinking for some reason to put the Start Station at 240 and the End Station at 100. Brain fart. Have a chuckle at my expense.

[Author]

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