What does Green indicate on the Flooding Effect Diagram?

• A. Stability increases despite Free Surface existing
• B. Stability decreases if Free Surface exists
• C. Not significant
• D. Not used

Answer: (A)

Green indicates a net positive effect on stability in the Flooding Effect Diagram. This means that for that flooding scenario, the ship’s stability actually improves even though there is a free surface present. The reason is that the added floodwater, depending on where it accumulates, can lower the center of gravity enough or alter the buoyancy distribution so that the metacentric height (GM) increases, or the righting lever remains favorable, offsetting the typical stability loss caused by free surface. In other words, despite the free surface effect, the overall balance of weight and buoyancy in that scenario yields a more stable condition.

This is why the green label appears: it marks scenarios where flooding leads to a gain in stability rather than a loss. The other descriptors—indicating a decrease, not significant, or not used—do not apply to these cases, since the diagram is specifically conveying the net positive stability outcome for that flooding configuration.