All About Estuaries
In Westeros, there are several bodies of water and places named for the abundant sea life these estuaries support: the Bay of Crabs, the Bay of Seals, and Seal Rock, for example. Other great bays in Westeros centered on estuaries include Blackwater Bay, the Whispering Sound, the bay along Lannisport, and the bay containing the Shield Islands. Great cities in Westeros are also frequently found near estuaries or their associated rivers: King's Landing, White Harbor, Highgarden, Oldtown, and Starfall are all closely linked with estuaries or an associated river. There are also a number of important ports, cities, and holdfasts found throughout Westeros along estuaries, including Maidenpool, Casterly Rock, Moat Cailin, and Heart's Home. In Essos, important cities like Braavos and Astapor also sit on or near estuaries. These cities show that the richest cities are nearest the estuaries.
The estuaries of Westeros are surrounded by different types of terrain. King's Landing includes high hills that offer a strategic advantage in defending the city, but waterfrontage that Tyrion Lannister used to great effect in the Battle of the Blackwater. Oldtown is a large city near the Whispering Sound, and is a very rich city in which the Citadel, the Hightower, and the Starry Sept (the first capital of the Faith of the Seven). White Harbor, found on the the White Knife river and the Bite bay and is the only real city in the North and one of the richest city in Westeros. The New Castle of the Manderly family is found on top of a hill overlooking the city, on which the Castle Stair road between the castle and Wolf's Den. Starfall was the former capital of the Kings of the Torentine, located where the Torentine River empties into the Summer Sea and is surrounded by the western Red Mountains.
[https://upload.wikimedia.org/wikipedia/commons/b/ba/Marseille_Vieux_Port_Night.jpg]
Throughout Westeros, the physical and ecological environments affect the cultures of the populations therein. Northern populations are always aware of the winter cold, while in the lower Reach, even noble house members have never seen snow. The House Redwyne in The Arbor island has a large navy and associated culture. The desert in the Dorne has made wet locations such as the Water Gardens and the Greenblood well-loved places.
Cities near large estuaries take advantage of them for their incomes. White Harbor relies on the marine trade and fishing grounds associated with the river and the bay. King's Landing relies on supply chains from around around the world to provide the kings with the best foods, goods, and supplies from around Westeros and the broader world.
There are some places that have such particular physical environments that the skills people get from growing up in one of them become useful in places far from home. For example, at the start Brienne's journey with Jaime and Cleos Frey on the Trident,
The Red Fork was wide and slow, a meandering river of loops and bends dotted with tiny wooded islets and frequently choked by sandbars and snags that lurked just below the water's surface. Brienne seemed to have a keen eye for the dangers, though, and always seemed to find the channel. When Jaime complimented her on her knowledge of the river, she looked at him suspiciously and said, "I do not know the river. Tarth is an island. I learned to manage oars and sail before I ever sat a horse."
Beyond boating being known to someone growing up on an island, there are other skills likely for many different types of terrains that can be useful elsehwere. For example, in the Vale of Arryn, there is a "glacial river" through the Mountains of Moon that "flows into a narrow bay of the narrow sea" In Dorne, the Torentine River flows through the Red Mountains into the Summer Sea. While these estuaries are in different regions, and the cultures of residents of them are likely to be different, there are likely to be some behaviors that are similar. For example, taking advantage of the fishing grounds in the estuaries would feed the people and improve the economy of each location.
Those are just two key example of how the skills one gains growing up in a particular physical environment may be useful in others far from where one grew up. As with Brienne's ability to navigate the Trident safely despite not having to
Being able to travel through the mountains would be more likely for the people living in mountains. Teaching children to swim and boat would be a way for parents to prevent children from drowning for locations near water, especially islands. Growing up in Tarth made Brienne able to navigate the Trident. Similarly, While the culture of the Vale and the Torentine would likely be quite different, someone from the Vale would probably not find the Torentine area totally unfamiliar.
The two photos below show two distinct mountain river valleys in the real world: one in an otherwise dry and arid environment, the other in a lush, snow-capped range of mountains. It's easy to imagine the Red Mountains in the photo above and the Mountains of the Moon in the scene below.
[Ximonic (Simo Räsänen), CC BY-SA 4.0 <https://creativecommons.org/licenses/by-sa/4.0>, via Wikimedia Commons]
Aside from Brienne, are there any other examples of characters from one such region who may have traveled to another and made use of skills learned at home? Certainly. We know House Manderly moved from the Mander River to the White Knife/Bite intersection -- the estuary. A warm-weather house moved to a cold-weather region, and was able to set up well there. These were not mountainous regions, but it illustrates the point of how the local terrain and water resources may be more important to how a family lives than the greater biological and ecological region.
Stay tuned for the next installment of Estuaries of the Seven Kingdoms for the answer to one of the biggest unanswered questions in A Song of Ice and Fire: Ashara Dayne.
