Warnings
What each open channel warning means: overflow, near-critical flow, a discharge that drops with depth, and unusual roughness.
- Overflow. The discharge is more than the bank-full capacity: the water leaves the section over the lower bank.
- Near-critical flow. With , the water surface tends to be wavy and unstable.
- Discharge drops with depth. Between two water levels the section carries less as the water rises: more than one depth can carry the same discharge. Give the floodplains their own , so each part is computed apart.
- Unusual roughness. The of a segment is outside 0.010–0.150, the usual range from smooth concrete to dense vegetation. The engine still computes.