Horizontal alignment

Horizontal alignment is the plan layout of a navigation channel: its centerline, the straight reaches, and the bends that connect them. PIANC keeps bends as few and as gentle as practical because a turning ship needs extra width, and the channel is widened on bends to cover the swept path and the drift angle the vessel carries through the turn. Bend radius is set against the design vessel length, commonly 5 to 10 times the vessel length overall for an unaided turn, with larger radii where current or wind crosses the bend. Straight reaches are aligned with the prevailing current and wind where possible to cut the cross-component the helmsman must counter. The vertical counterpart is channel depth.