Leda barrage
The Ledasperrwerk at idle is used for flood control of behind the barrage lying commuting area of the rivers Leda and Jümme and its tributaries. Leda and Jümme drain a lowland area of around 35,000 hectares that is inadequately protected against high floods by relatively low dykes . Since the increase and strengthening of dykes would have been possible only with great technical and financial difficulties began before the Second World War with the plans for a barrier in the Leda at idle, where the river into the Ems flows . Planning came to a standstill during the war, but was resumed after the war.
concept
In 1949, the then water and shipping office in Leer presented a draft for the barrage.
In order not to influence the natural water and tidal conditions, the Leda barrier is usually open. Only when the water level is expected to be 50 cm above mean high tide (MThw) are the gates of the barrage closed at low tide (TNw). However, it is also possible to close it at a later date when the water runs up.
This concept differed significantly from conventional sewage systems and the first tidal barriers, which switch off the influence of the tides in protected waters. In 1953, when the construction work on the Leda was already well advanced, the flood disaster in the Netherlands and Great Britain led to similarly functioning, albeit in some cases much larger, systems being built at the mouths of the Thames and several Dutch rivers. There are also numerous storm surge barriers in Germany .
Construction of the Leda barrier
The Federal Waterways and Shipping Administration (WSV) planned and built the barrage. Construction began in September 1950. The barrage could be built in a dry Leda arch. After the barrage was completed, the Leda was turned over by a puncture about 1,000 meters long. The original course of the river is still there today in the form of an oxbow lake, which was separated from the Leda below the barrage. In July 1954 the plant was put into operation. Only five months after commissioning, the barrage passed its first practical test in a series of storm surges .
Technical specifications
The barrage was built according to the principle of a rifle defense . It has five openings, each 14 meters wide. The lifting gates, each 10.5 meters high, can be lowered onto the threshold between towers.
- Width of the barrage: 94 meters
- Width of the openings: each 14 meters
- Number of openings: 5
- Height of the lifting gates: 10.5 meters
- Total height of the middle towers (from the threshold): 23.5 meters
- Clearance height (at MThw): about 3.75 meters
- Clearance height (at MTnw): about 5.10 meters
The Leda barrage, which no longer meets today's safety requirements due to its age, is relieved by the Ems barrage near Gandersum, which was put into operation in 2002 .
For maintenance work, the individual openings can be sealed with emergency closures and then pumped out.
The operator of the barrage is the Emden Waterways and Shipping Office .
Storage polder
Part of the barrage is the relief structure built in 1956 and 1957, which can feed the empty polder south of the Leda with upstream water. The approximately 135 hectare storage polder has a capacity of 3.2 million m³. It belongs to the Leda Jümme Association .
Leda pumping station
From January 2000 to December 2001 a pumping station was built in the immediate vicinity of the Leda barrage . The pumping station, which was planned and built by the Lower Saxony State Office for Water Management, Coastal Protection and Nature Conservation ( NLWKN ), has a pumping capacity of 40 m³ / s. This means that almost 3.5 million m³ of water can be pumped out of the area behind the barrage per day, and thus slightly more than the entire capacity of the Leeraner storage polder.
The pumping station improves flood and storm surge safety in the Leda-Jümme area, as it can pump the headwater out of the Leda when the barrage is closed for a longer period of time, where the outflow from the inland is dammed. This prevents the Leda-Jümme area from being flooded by dammed water.
The pumping station can also be used for ship overpasses on the Ems and when the Ems barrage is closed it can help fill the storage space of the Ems with water from the Leda. As a result, the required water level in the Ems should be reached as quickly as possible in order to minimize interventions in nature through a shortened damming time.
literature
- Paulheinz Gursch: The Leda barrage in East Friesland. In: The Coast , 14 issue 2 (1966), pp. 107–156 ( PDF file , 13.1 MB).
Web links
Coordinates: 53 ° 12 ′ 50 ″ N , 7 ° 28 ′ 22 ″ E