Establishing a "Good Ecological Potential" of the Münster Aa, a hard-sealed urban channel – a technical design of hydraulic and ecological niches

Basic data for this talk

Information about the event

Abstract

The "Münster City Aa" (West Germany), a third order lowland stream, is a hard-sealedurban channel stretch with high runoff variability. The city of Münster is encouraged toestablish "good ecological potential" for the channel. With a eutrophic man-made lakeupstream, it corresponds to the synthetic water type "lake-outlets of German lowlands".The challenge is to meet the requirements of the WFD considering high seston transportand effective flood protection. In 2012, a pilot reach was installed in the urban Aa fortesting technical solutions of ecological enhancement. The concrete bed was replacedby sediment mixtures and morphological structures. Additionally, various technicalchoriotopes were installed according to ethohydraulic demands of water type-specificbenthos. Morphodynamic simulations and measurements confirmed complex shearstress processes causing sediment instabilities near structural elements. Nevertheless,macroinvertebrate diversity increased significantly in the pilot reach compared to theprevious situation and more parsimonious solutions. Long-term stability and flowbalance were studied on technical choriotopes for a stocking with water type-specificfaunal elements. Hydraulic and morphological variability are discussed as promoters of biodiversity but also as a principal limitation of ethohydraulic solutions.

Speakers from the University of Münster

Dorner, Simon	Department of Limnology
Meyer, Elisabeth Irmgard	Department of Limnology
Riss, Hans-Wolfgang	Department of Limnology