The River Glyde is a classic Irish lowland river flowing approximately 35 miles in a southeasterly direction before emptying into the Irish Sea at the picturesque seaside village of Annagassan in County Louth. The river owes its origins to a series of smaller tributaries rising in Counties Cavan and Monaghan, including the Tubermannin and Killany Rivers, both of which hold stocks of brown trout. The upper reaches of the Glyde are known as the Lagan River, which is deep and slow flowing. The Lagan and Killany Rivers meet at Tully in County Louth to form the main River Glyde. The catchment drains approximately 391 square kilometres of mid-Louth, with the river rising at an altitude of around 300 metres on the Cavan-Monaghan borders. The Glyde's two principal tributaries are the Longfield River, draining the Carrickmacross area, and the Lagan River. The river's meandering course through agricultural lowland landscapes creates ecological corridors and provides gravelly substrates ideal for fish spawning. The Glyde and neighbouring River Dee join together approximately one kilometre from the sea at Annagassan at the southern end of Dundalk Bay.