The River Laune flows approximately 20 km to drain Killarney’s Lough Leane into the sea at Castlemaine Harbour. The Laune carries most of the rainfall from the MacGillycuddy Reeks, Ireland’s highest mountain range. Many streams on the south side of the Reeks drain into Killarney’s Upper Lake before filtering down to Lough Leane. As the River Laune drains Lough Leane to the sea, it is fed by two rivers running north from the Reeks, the River Loe from the Gap of Dunloe and the Gaddagh River from the heart of the Reeks. Another tributary, the Cottoners River, carries rainwater from the west of the Reeks. On the southern side of the bridge, a low embankment runs upstream for about 1 km towards Killarney. This is part of over 40 km of embankments that prevent the sea from flooding low-lying land around Castlemaine Harbour. These embankments exist due to Napoleon’s dominance in Europe around the year 1808. The British government were looking for alternative sources of hemp to make sailcloth for their navy to defend against a possible invasion.