Description
The flow direction lines determine how the banks of the river are assigned their output height values. Each water body polygon must have an inflow and outflow direction lines that intersect its boundary. The inflow lines indicate the upstream position of the water body, and the outflow indicates the downstream position. If flow direction lines are present but not identified, the lines may not intersect the boundary of the water polygon.
Solution
Create inflow and outflow present in the flow direction features.