The effect of the growth of macrophytes and mowing patterns on the discharge of lowland rivers.


In the Netebasin in Flanders the discharge capacity is an important function and the growth of macrophytes can lead to a stowage of water with inundation as a consequence. To avoid these problems the vegetation is removed annually. This kind of management has a lot of ecological consequences for the present communities. A more ecological management with partial vegetation removal is an acceptable compromise between a sufficient discharge of water and the integrity of the water vegetation. At the moment there is a lack of fundamental information on such mowing pattern. The purpose of this project was to search for an ecological responsible management that does not jeopardize the discharge capacity. The project has 4 research areas :1. The development of macrophytes in the Nete basin2 .The relation between macrophytes and water discharge 3 .The effect of mowing patterns on the discharge capacity4 .Conclusions and recommendations The average quantity of macrophytes was higher in the basin of the Klene Nete than in the Grote Nete basin. The biomasses in the upper streams are lower than in the more downstream parts of the basin which is a consequence of the higher acidity in the upper stream parts of the basin. The period of maximal biomass lies between May and Septembre for the different locations. In the future it would be wise to link the period of mowing to the dominant taxa or the from ecological point of view interesting taxa. The effect of vegetation on water discharge is that the stowage increases with increasing water velocity. The highest roughness coefficient (Manning-n) values are those from shallow brooklets with low discharges. With increasing biomasses the stowage will increase and the roughnesscoefficient will rise. Mowing in patterns can reduce the stowage from 40 till 88%. The efficiency in which the patterns improve the discharge was not different between the vegetation types, namely a submersed and mixed vegetation type. To avoid negative effects on the plant communities the mowing has to be as late as possible. If the circumstances demand that the vegetation has to be removed the mowing in patterns is an acceptable alternative. The type of pattern one has to use is dependent of the situation, the desirable reduction percentage for decline and the feasibility on the terrain.


mowing patterns, macrophytes, manning-n, netebasin


Belgium {Geographical scope}
Inland Waters {Habitat type}


Name Role Start End
Meire, Patrick promotor


Name Role Start End
Ecosystem Management Research Group unknown

created:2011-12-14 14:18:59 UTC, source:iweto

© 2012 by the Belgian Biodiversity Platform