Bustling with ships from both inland and oversea, Port Dirwen is the main commercial harbor of Valone, located in the riverside of Dirwen River with the Valonus Bridge in between. It's been used widely for transporting goods across the Valonia Empire, especially the merchants ship and foreigners, and most importantly, collecting fees.
One of the empire's income comes from the Waterway Policy. First adapted on Valone itself, all coastal cities within the empire's territory have to follow the formula such as Auqapus.
It's a simple rule: All the ships, enter or exit, must and pay fees first in order to pass the bridge. Fees are usually an amount of Sart or equivalent, depending on cargo and fleets. The larger the ship caravan, the more fee to pay. So, the price is usually suitable for most businesses.
However, if not enough fees are paid, they'd be requested to turn back the ships or find money for a limited time. If they intend to violate the law by passing through or stomping the bridge for example, a force will confront.
The diplomacy relationship can reduce the complication with privileges. For examples, the Irgian-Valone Pact allows all the republic ships to pass to almost no cost, whereas their common enemy, Maritime Kingdom, charges double.
9/8/2022 - Minor edit