How did shallow draft limit a coastal ship's guns?

Was there a tradeoff between shallow draft for coastal work and the largest gun the ship could carry?

Yes; Libertad's riverine requirement likely limited the design to 9.4-inch guns, while a larger hull could have carried 12-inch weapons.

Shallow water limits how much hull volume and displacement a designer can place beneath a heavy gun mounting. Libertad's 9.4-inch battery is linked to the requirement for a riverine battleship. A somewhat enlarged design could have carried 12-inch guns, but it would no longer have met the same size and draft constraints. The answer demonstrates how local geography can set the upper bound on firepower even when a navy wants a powerful deterrent.