ABSTRACT
Restoration of the Eggrank Bend at the Thur River near Andelfingen (Canton of Zurich, Switzerland, HQ 100 = 1400 m3/s) comprises five micro groins of 30 to 50 m length as well as a snail shaped groin. Micro groins are overflowed already at low flow conditions and allow reduction of flow velocities at the outer bank as well as flow diversification. In addition, the inner bank slope was regraded, deadwood was introduced and a new gravel embankment was created upstream of the bend. To gather a maximum of knowledge and conclusions about the functionality and efficiency of the restoration measures at the Eggrank Bend, intensive monitoring is carried out. Monitoring campaigns contain 2D flow velocity recording by Large-Scale-Particle-Image-Velocimetry (LSPIV) from drones and measurement of flow velocities and cross section geometries by 3D Acoustic-Doppler-Current-Profiler measurements (ADCP). First results show a reduction of the bend scour depth from initially around 3.6 m for mean discharge conditions to almost zero. The main flow is not following the outer bank any more but is more equally distributed over the entire cross section.
