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Third field visit to the transboundary catchment of the Othene

This field visit gave us a chance to get an overview of the South-West Othene creek restoration project. The day started with an explanation of the origins of the area, completed with a description of its current situation.

Photo 6: Presentation OtheneOriginally, Zeeland consisted of dunes and peat bogs, which protected the area from the sea. Since 1100 BC, the soil level has been dropping, mainly due to drainage and peat extraction by the inhabitants. Due to a lot of flooding, the area changed into a lot of small islands as a result of which the peat bog was washed away and clay was deposited. The areas were criss-crossed with creeks which were in contact with the sea. Later, these creeks were higher as a creek becomes filled with sand if the flow stops. The sand does not lose any volume, but the surrounding peat bog does. The Othene creek has an exceptional geomorphology; the area consists of a Pleistocene sand-cover where, due to creeks breaking through, tidal sediments were laid down. Part of this sand cover is buried under clay. All of these gradients together make this creek area like no other. Many ScaldWIN partners had no experience with this type of creek. For the local partners present, the ScaldWIN project was also introduced in order to get a broader view of the local approach.
For  making the right decision concerning the removal of the fish migration bottlenecks, a water system analysis was carried out from which it appeared that it is possible to raise the water level in parts of the area. In the Netherlands, the water level is traditionally controlled with weirs. To this end, an unnatural level is generally created which is higher in the summer than in the winter. The difference, on average over the whole management area, is 15 cm but can increase up to 50 cm in a few weir areas, which can be done to protect the soil from winter flooding and still give it sufficient moisture in the summer. Because this is not favourable for the ecological value, an attempt is made to reduce the difference in water level between winter and summer to a maximum of 20 cm.
If the level in the area is raised, a number of weirs can be removed, creating a large area with the same water level. The water system consequently becomes more robust and both agriculture and nature will have better water management. Within this area there are no more obstacles for fish.
Downstream, the weir at Buthduiker will be made passable, as well as the weir on the Moerspui waterway upstream, in the direction of Flanders. The fish passage planned for the Buthduiker is now ready, but not yet in place. For this, the smallest species of migrating fish, the three-spined stickleback has been taken account of. To bridge the difference in level, a fish ladder has been designed with 19 chambers and a resting chamber. Larger species will also be able to use this fish ladder.
Photo 7: The Fish PassageThe investments within the ScaldWIN project fit within a global vision of the region which aims to let the architectural landscape to come into its own, as well as the historical and cultural value of the surrounding area. To this end, the Province of Zeeland is collaborating with the Zeelandic Flanders Forestry Commission. In this region there are a lot of remains dating from the Eighty Years’ War, the revolt by the Dutch against Spanish rule (1568 – 1648). At this location a lot of restoration work is still being carried out to restore the State-Spanish lines to their former glory.

After a morning packed with interesting explanations and with  a full stomach we were able to board an orange bus (after all, we were in the Netherlands) to investigate on site what this mau mean in concrete terms for the region.

We discovered a very pretty area which even more attractive by the perfect weather. We visited the Buth weir on the Axel creek and went for a long walk via the State-Spanish Line (and the forts restored by the Zeelandic Flanders Forestry Commission) as far as the Moespui waterway and the last weir before the Belgian border. This will not be removed, but the difference in level will be removed on the condition that a number of lower fields can be purchased in order to transform them into a nature reserve. This conversion to wetland will prevent the current fields coming under water due to raising of the water level.
Photo 8: The landscape of OtheneNot only did we learn a lot about this part of the project, the walk was also an excellent opportunity to improve the contact between the various ScaldWIN partners. At the end of the walk, our orange bus brought us back to Terneuzen.

Our next visit will be to the latest partner who has planned concrete investments for fish migration. On October 20, 2011 we will visit the Eastern Dender in Wallonia.