Country and state develop
"flexible tidal control"
The country and state have agreed on a joint technical model for declaring war on silt contamination in the Ems: the gates of the Ems Barrier should control the tide in such a way that the ebb current carries more sediment out of the Ems than the current prevailing flow current carries into the river. The fundamental feasibility of the "flexible tidal control" was verified in two feasibility studies conducted by the Federal Waterways and Shipping Administration (WSV) and the Lower Saxony State Organisation for Water Management, Coast and Nature Conservation (NLWKN) with support from renowned technical assessors. Based on this, on 25 January 2017 the Steering Committee of the Master Plan Ems 2050 assigned the preliminary work for a permit process that should result in an approvable, detailed plan. The contract partners expect the tidal control to begin in 2020.
The federal and state governments had previously followed different models. The federal weir aimed to raise low tide levels, and the NLWKN wanted to halt the flow current. Both sides now favour a concept that primarily affects flow current because the greatest possible effects can be achieved this way. However, a method for lifting low tide levels is also still in place. This concept includes many control methods for being able to respond flexibly to all Ems-related situations – including the demands of interior draining and ship transit. An operating plan is to be developed during the public law permit process in which all affected parties are involved.
Leading up to the process, the Federal Waterways and Shipping Administration held discussions with representatives from shipping, port administration, and port-related companies. The closing times of the Barrier will impair ship traffic along the Ems. These exchanges aim to determine ways of minimising these restrictions while simultaneously ensuring the effectiveness of the silt retardant.
The model calculations from the Federal Waterways Engineering and Research Institute predict that the spatial impact of the flexible weir on the silt will reach as far as Knock, beyond Emden. If the plans are finalised successfully, current information from the Federal Waterways Engineering and Research Institute (BAW) foresees the construction of the first storm flood structure for the planned and permanent control of the tide in a river course. The Barrier need not be structurally altered for this purpose, but the riverbed above and below the structure must be reinforced with stone bed protection in order to prevent erosion. An administrative agreement concerning the distribution of the foreseeable overall expenses of about 30 to 40 million euros is being negotiated between the state and federal governments.
The decision that has now been made consolidates two of the three measures for improving water quality, for which the contract partners commissioned feasibility studies in March 2015: a weir adjacent to, and tidal control with, the Ems Barrier. In order to reach the desired results as quickly as possible, the contract partners of the Master Plan Ems 2050 agreed to implement the scheduling process before the feasibility study for the tidal reservoirs on the Ems – the third improvement measure, expected by late 2018 – is available. Should the tidal reservoirs prove feasible and effective, they can be combined with the flexible tidal control. Furthermore, the expected minimisation of silt in the Ems should have a positive effect on the planned establishment of habitats in tidal polders along the Ems. They would not be contaminated by silt as quickly as current conditions allow.