I saw my volume accounting error as high as 11% in a simple 1D-2D coupled model when using landcover manning’s n setting, however, if I discard the landuse manning’s n and instead use an uniform manning’s n as 0.06 for the entire 2D area, the error is less than 1% (all other conditions are kept the same). I want to see how I can solve this issue (applying landcover data manning’s n is required by the client). Thanks.
Do you see instability at 1D2D connections i.e. lateral structures? Each cell only gets one manning’s n value and it is based on the larger land cover area underneath the cell. What are your lateral structure weir coefficients? Have you increased the Lateral Structure flow stability factor from 1 to 3? Have you played with your computation time interval?