Negative flow in BC when using stage hydrograph in fully 2D models

[suchab]

Hi,

I want ask if there is solution for negative flow rates in upstream BC. I have quite simple model with stage hydrograph BC in northern part of the 2D model and normal depth in southern part of the 2D model. The result flow vector indicate that the flow direction is southwards like it should be, however, in the Stage and Flow hydrograph window the flow rate is negative. I find out in the HEC-RAS manual that the direction how you draw the BC in Geometric Data viewer can affect the positive flow rate direction.

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Negative values in flow only appears when I used stage hydrograph as input. When I use flow hydrograph the flow rate is positive. The flow rates seemed reasonable since I made same model with flow hydrograph with similar flow rates and the results were similar. Only difference was that the flow values were negative.

Is there any easy way to determine the downstream direction in completely 2D models like in https://therassolution.kleinschmidtgroup.com/ras-post/hec-ras-model-with-2d-mesh-only/?

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