Remove or modify in-channel hydraulic structures
Contents
- 1 Remove or modify in-channel hydraulic structures
- 1.1 General description
- 1.2 Applicability
- 1.3 Expected effect of measure on (including literature citations):
- 1.4 Temporal and spatial response
- 1.5 Pressures that can be addressed by this measure
- 1.6 Cost-efficiency
- 1.7 Case studies where this measure has been applied
- 1.8 Useful references
- 1.9 Other relevant information
Remove or modify in-channel hydraulic structures
Remove or modify in-channel hydraulic structures06. In-channel structure and substrate improvement
General description
In few words: Remove in-stream hard structures to allow natural processes to re-establish
Groynes or wing deflectors are commonly employed at rehabilitation projects as structures for modifying the dynamics and directing the flow, increase the complexity of the substrate and the water level. There are many kinds of wing deflectors, but rock and rock-filled log crib deflector structures are the most common. When they are placed in sand bed streams it might be needed to put a filter layer or geotextile underneath the deflector for a correct settlement.
Since they redirect the flow and narrow the width of the channel, microturbulences are created even at low flows. Sometimes these microturbulences alternate the sediments size distribution, diversifying the substrate structure and enhancing habitat diversity.
On the other hand, these structures might be degradation source, since the turbulences created and a higher flow velocity can cause streambanks and channel bed erosion (figure 1). The backwater effects would damage riffle areas if they are placed too near to upstream riffles. Flooding frequency and periods of inundation might be intensified by increasing channel roughness.
Applicability
Expected effect of measure on (including literature citations):
- HYMO (general and specified per HYMO element)
- physico � chemical parameters
- Biota (general and specified per Biological quality elements)
Temporal and spatial response
Pressures that can be addressed by this measure
- Channelisation / cross section alteration
- Alteration of instream habitat
- Embankments, levees or dikes
- Artificial barriers upstream from the site
- Artificial barriers downstream from the site
Cost-efficiency
Case studies where this measure has been applied
- Charlottenburg wave-protected shallow
- Chícamo Life project. Conservation of Aphanius iberus´ genetics stocks ( Murcia ).
- Regelsbrunner Aue
- Vén Duna - side arm reopening
- Opijnen - Side Channel
- Vreugderijkerwaard - Side channel
- Klebach - Side channel
- Thur
- Narew river restoration project
- Bouxweerd - Artificial pool
- Töss
- Stream -mending the Avon
- Sella
- Drava - Kleblach
