Thank you for your help, Aurelian.
I solved my problem by expanding the cross-section for the floodplain. It seems to be too narrow to let water flow.
I hope I still will receive your help for my problem in the future.
P/s: I have a question: You are the member of DHI Czech who came to Polytech Nice and taught something about MIKE OPERATION for Master 2 students, don't you? I am one of them.
I am building a model to connect main river and floodplain via link channel. Because I don't have any cross-section of floodplain so I created something for this by myself and when I try running MIKE 11 I received an error below here:
[b]Error no 69: At FLOODPLAIN 2: 0.000 meter, the calculated hydraulic radius is non-positive. The water level is 17.1 meter.[/b]
I tried to change the width of cross-section but not correct. I hope to will receive your help.