I just read “The World of Ice and Fire,” and the description says that the Mander is the largest river in Westeros. However, it all said the upper reaches of the river (the area around Bitterbridge and beyond) are rough and muddy and can only be traveled by shallow-drafted boats rather than seagoing vessels. Therefore, for the Mander-Blackwater canal you proposed, would you first dredge this area of the river, or for transporting grain to King’s Landing would you only need barges and the like?