Difference between revisions of "Add sediments"
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Add sediments06. In-channel structure and substrate improvement | Add sediments06. In-channel structure and substrate improvement | ||
==General description == | ==General description == | ||
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| + | The incision of the riverbeds has been widely observed on many streams of mobile bed. Incised channels occur when stream power exceeds the channel bed’s resistance, or when sediment output exceeds the sediment input to the reach. | ||
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| + | This is frequently due to the overexploitation of the riverbed alluvial (gravel mining) wich typically results in smaller bed substrate, and thereby reduces the stream power necessary to mobilize it. Other human alterations causing channel incision are stream channelization and straightening, construction of levees, encroachment of walls stream cleaning, large wood removal, changes in land use, upstream dams, etc. The technical solution to implement will depend on the geodynamic characteristics of the stream to restore and especially the intensity and nature of its current sediment transport. | ||
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| + | The most efficient long-term solution is to restore the river space for mobility, allowing the natural channel dynamics to reshape the channel (at its longitudinal, lateral and vertical dimension) resulting in a quasi-equilibrium state, having just the right morphology to move the sediment and water carried by the river. | ||
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| + | When it is not possible to achieve this solution, it may be interesting to raise the level of the riverbed and ameliorate the substrate composition and structure with measures like the presented at this section, among we find the addition of sediments. | ||
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| + | Gravel and sand augmentation: Adding washed gravel and sand to a channel is a mitigation or rehabilitation measure of the hydrogeomorphic conditions of the stream. The aims of this measure are (Elkins et al., 2007): | ||
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| + | :• Reduce bed armoring | ||
| + | :• Improve bed substrate quality | ||
| + | :• Increase flow velocity | ||
| + | :• Reduce water depth | ||
| + | :• Increase habitat heterogeneity | ||
| + | :• Increase hyporheic exchange | ||
| + | :• longer duration of floodplain inundation | ||
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==Applicability == | ==Applicability == | ||
==Expected effect of measure on (including literature citations): == | ==Expected effect of measure on (including literature citations): == | ||
Revision as of 15:46, 3 September 2010
Contents
- 1 Add sediments
- 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
Add sediments
Add sediments06. In-channel structure and substrate improvement
General description
The incision of the riverbeds has been widely observed on many streams of mobile bed. Incised channels occur when stream power exceeds the channel bed’s resistance, or when sediment output exceeds the sediment input to the reach.
This is frequently due to the overexploitation of the riverbed alluvial (gravel mining) wich typically results in smaller bed substrate, and thereby reduces the stream power necessary to mobilize it. Other human alterations causing channel incision are stream channelization and straightening, construction of levees, encroachment of walls stream cleaning, large wood removal, changes in land use, upstream dams, etc. The technical solution to implement will depend on the geodynamic characteristics of the stream to restore and especially the intensity and nature of its current sediment transport.
The most efficient long-term solution is to restore the river space for mobility, allowing the natural channel dynamics to reshape the channel (at its longitudinal, lateral and vertical dimension) resulting in a quasi-equilibrium state, having just the right morphology to move the sediment and water carried by the river.
When it is not possible to achieve this solution, it may be interesting to raise the level of the riverbed and ameliorate the substrate composition and structure with measures like the presented at this section, among we find the addition of sediments.
Gravel and sand augmentation: Adding washed gravel and sand to a channel is a mitigation or rehabilitation measure of the hydrogeomorphic conditions of the stream. The aims of this measure are (Elkins et al., 2007):
- • Reduce bed armoring
- • Improve bed substrate quality
- • Increase flow velocity
- • Reduce water depth
- • Increase habitat heterogeneity
- • Increase hyporheic exchange
- • longer duration of floodplain inundation
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
Cost-efficiency
Case studies where this measure has been applied
- Vääräjoki - Niskakoski
- Kuivajoki - Hirvaskoski
- Carrión
- Blenheim Palace Project
- Inchewan Burn Bed Restoration
- River Brent at Tokyngton Park
- River Wensum Rehabilitation Project - Bintree
- Stora
- Amesbury - Demonstrating strategic restoration and management STREAM (LIFE05 NAT/UK/000143)
- Chilhampton - Demonstrating strategic restoration and management STREAM (LIFE05 NAT/UK/000143)
- Fovant - Demonstrating strategic restoration and management STREAM (LIFE05 NAT/UK/000143)
- Conservation of Atlantic Salmon in Scotland (LIFE 04/NAT/GB/000250)
- Hampshire Avon - Seven Hatches
- Ruhr Binnerfeld
