North and south of the Gladden Fields the current of the Anduin is very strong, but where the Gladden flows into the Great River, the current reduces and thus the boggy area of the Gladden Fields is created.
Near this place, at an slope east of the Anduin, Isildur and his sons were ambushed by Orcs when they marched back towards Arnor. Isildur's sons were killed in that battle, whilst he himself attempted to escape using the power of invisibility of the One Ring. He ran towards the Anduin and tried to cross it. Due to the current he reached the western bank near the river Gladden. But the Ring had slipped from Isildur's finger and when he stood up he was seen by Orcs, who laid there to kill any survivors of the ambush, and was killed by their arrows.
It was here, twenty-five centuries after the ambush, that the hobbit Déagol retrieved the One Ring from the Gladden and he was killed by his cousin Sméagol, who became the evil creature called Gollum.
Tolkien suggested to translators to avoid if possible the 'learned' name iris.