River Liffey (Dublin, Ireland)

River Liffey (Ireland)

          

The river Liffey is one of the most important rivers in Ireland, it accounts for 60% of Dublin’s fresh water. It flows through three counties, Wicklow, Kildare and Dublin and stretches over 82 miles long. At its source, the Liffey is only 12 miles from the ocean, but as we know gravity guides water and adds an extra 70 miles to its journey from the mountains to the ocean. Upon first seeing the Liffey the first thing you notice is the dark brown color of the river. This signifies a rough ride from the source to the mouth of the river.

The Liffey starts at its headwaters in the Wicklow mountains at an elevation of 1,600 feet between the Kippure and Tonduff mountains. The terrain is rough and full of large granite rocks deposited from glaciers. Not an easy hike, and comfortable shoes are needed. The Wicklow mountains are known for their heavy rain fall and this causes a lot of sediment production.

 The sediment production is extremely corrosive, as the rain fall in this mountain range is continuously year long and can become extremely powerful in the wet winter months. This makes the Liffey a perennial river as the large rainfalls keeps the river in constant motion. At its source, the water has a turbulent flow which can quickly change and sculpture the path of the river and the terrain. The terrain that surrounds these mountains is mainly consisting of granite with a top level of mud and clay. The bed of the river in this region is bedrock with very little dirt, which makes the river’s water clear. The banks of the river are surrounded by rough pointy granite, in which the river has eroded the top level of soil exposing the granite. This makes the terrain extremely vulnerable against large volumes of rain fall and has resulted in the formation of a V-shaped valley that flows between the Kippure and Tonduff mountains. This V-shaped valley is where its major tributaries include the River Dodder, the River Poddle and the River Camac flow into one to make the Liffey. Flooding in this area is highly unlikely as the gradient slopes down to the lowlands.

As the river makes its way down from the mountains, we find its path has brought it to County Kildare. When it reaches this area, the river reaches its Sediment transport area. Here the rivers discharge slows down, and the erosion is not as damaging as the sediment production stage. This is where the Liffey water starts to darken as the runoff from the Sediment production slows down to produce a dark murky water.

Dendritic pattern is the most prevalent drainage pattern on the Liffey’s path. This is due to the slope of the land. The Liffey starts at the top of a mountain and works its way down to the ocean. But a funny fact about the Liffey is that at its source it is only 12 miles from the ocean, but because water is influenced by gravity, it slopes away from the ocean and heads back into mainland Ireland.  This region is mainly limestone and this sediment rock is weak against the corrosive powers of the river. The gradient in this area is almost flat, but the powerful force of the rivers flow velocity from its source helps the river carve its way through this region. This causes the river to meander through the flat lands of Kildare (Known for its flat and fertile agricultural land). Due to its geographical location, Kildare is considered a flood plain and usually floods after a heavy week of rain. Although both sides of the river have natural levees, they are unable to hold the overflow in heavy rain conditions. Both sides of the riverbed are surrounded by back swamp, which indicates that floods are very present in this area.  Luckily most of the land that surrounds the river is agricultural land and does not cause a mass concern for large populated towns in the region.

This has caused the formation of many Oxbow lakes along the rivers path, shortening the gap to the ocean. Most of these Oxbow lakes have dried up but in some ephemeral cases at high water levels some of these Oxbow lakes can become part of the river again until the water levels retreat.

As the river reaches the graded conditions downcutting becomes less dominant. The meandering pattern causes the energy of the river to erode the sides or banks of the river, resulting in the valley widening. At its heaviest turbulent flow, the Liffey is measured at 25 feet wide, but once it reaches its graded conditions the river can widen up to 70 feet wide.

Sediment Deposition is where a river meets the ocean, for the Liffey this happens in the heart of Dublin City. In the Gaelic language Dublin is known as Baile Atha Cliath, translated into English it means the Black River. This is due to the large discharge of water slowing down and turning into a laminar flow as it approaches the ocean. This murky water is a result of sediment deposition as the river loses power the sediment is deposited at the mouth of the river, resulting in a dark sediment depository consisting of mud clay and sand particles.  Most of these sediments are washed out to sea, but the Irish government does have to dredge the riverbed every couple of years. This is due to the fact that Dublin Port sits on the river’s mouth, and for hundreds of years this was a major port for trading importing and exporting goods. So, to keep this trade route open for business the delta which once sat at the rivers mouth has long being dredged so larger boats can enter the port.

As the river enters Dublin city, it is surrounded by large walls that act as levees. These levees have a 20-foot clearing from its water level. This is to prevent floods within the city, as history shows floods were not unusual until the building of these manmade levees. In the last century, Dublin city only flooded once since the levees were put in. So, this is a good indication that the city of Dublin is well protected from flooding.

One interesting fact about the Liffey is that it runs most of its course over limestone. This sedimentary rock formed millions of years ago beneath the sea. This has an important impact on the river as limestone is more alkaline, creating more conducive conditions for fish such as trout to thrive. This one of the main reasons Dublin became a settlement for its fresh water and unlimited fish.