Difference between revisions of "Mechanical removal of fine sediments (dredging)"

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=Classification table=
 
=Classification table=
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<table border="1">
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{| class="wikitable"
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<tr>
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! Classification !! Selection
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<td width="245">
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|-
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<p><strong>Classification</strong></p>
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|Fish species for the measure||[[Fish species for the measure::All]]
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<p><strong>&nbsp;</strong></p>
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|-
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</td>
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|rowspan = "3"|Does the measure require loss of power production||-
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<td colspan="2" width="361">
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|-
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<p><strong>Selection (multiple)</strong></p>
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||-
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</td>
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|-
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</tr>
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||[[Does the measure require loss of power production::Structural (requires no additional flow release)]]
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<tr>
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|-
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<td width="245">
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||Recurrence of maintenance||[[Recurrence of maintenance::Irregular at events]]
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<p>Fish species measure designed for</p>
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|-
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</td>
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|rowspan = "6"|Which life-stage of fish is measure aimed at||[[Which life-stage of fish is measure aimed at::Spawning / Recruitment]]
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<td colspan="2" width="361">
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|-
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<p>All</p>
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||[[Which life-stage of fish is measure aimed at::Juvenile habitat (0+)]]
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</td>
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|-
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</tr>
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||[[Which life-stage of fish is measure aimed at::Juvenile habitat (1+)]]
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<tr>
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|-
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<td width="245">
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||[[Which life-stage of fish is measure aimed at::Juvenile habitat (older than 1+)]]
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<p>Does the measure require loss of power production?</p>
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|-
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</td>
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||[[Which life-stage of fish is measure aimed at::Adult fish]]
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<td colspan="2" width="361">
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|-
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<p>Structural (requires no additional flow release)</p>
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||[[Which life-stage of fish is measure aimed at::Movements of migration of fish]]
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</td>
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|-
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</tr>
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|rowspan = "7"|Which physical parameter is mitigated||-
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<tr>
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|-
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<td width="245">
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||-
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<p>Recurrence of maintenance</p>
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|-
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</td>
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||[[Which physical parameter is mitigated::Substrate and hyporheic zone]]
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<td colspan="2" width="361">
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|-
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<p>irregular at events</p>
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||-
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</td>
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|-
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</tr>
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||-
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<tr>
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|-
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<td width="245">
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||-
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<p>Which life-stage of fish is measure aimed at?</p>
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</td>
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||-
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<td colspan="2" width="361">
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|-
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<p>All</p>
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|rowspan = "2"|Hydropower type the measure is suitable for||[[Hydropower type the measure is suitable for::Plant in dam]]
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</td>
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|-
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</tr>
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||[[Hydropower type the measure is suitable for::Plant with bypass section]]
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<tr>
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|-
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<td width="245">
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||Dam height (m) the measure is suitable for||[[Dam height (m) the measure is suitable for::All]]
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<p>Which physical parameter mitigated?</p>
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|-
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</td>
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|rowspan = "3"|Section in the regulated system measure is designed for||[[Section in the regulated system measure is designed for::Upstream of hydropower plant]]
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<td colspan="2" width="361">
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|-
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<p>Substrate and hyporheic zone</p>
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||[[Section in the regulated system measure is designed for::Bypass section]]
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</td>
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|-
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</tr>
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||[[Section in the regulated system measure is designed for::Downstream outlet]]
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<tr>
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|-
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<td width="245">
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|rowspan = "3"|River type implemented||[[River type implemented::Steep gradient (up to 0.4 %)]]
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<p>Hydropower type the measure is suitable for</p>
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|-
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</td>
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||[[River type implemented::Fairly steep with rocks, boulders (from 0.4 to 0.05 %)]]
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<td colspan="2" width="361">
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|-
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<p>Plant in dam</p>
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||[[River type implemented::Slow flowing, lowland, sandy (less than 0.05 %)]]
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<p>Plant with bypass section</p>
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|-
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</td>
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||Level of certainty in effect||[[Level of certainty in effect::Very certain]]
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</tr>
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|-
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<tr>
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||Technology readiness level||[[Technology readiness level::TRL 9: actual system proven in operational environment]]
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<td width="245">
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|}
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<p>Dam height [m] the measure is suitable for</p>
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</td>
 
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<td colspan="2" width="361">
 
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<p>All</p>
 
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</td>
 
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</tr>
 
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<tr>
 
−
<td width="245">
 
−
<p>Section in the regulated system measure is designed for</p>
 
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</td>
 
−
<td colspan="2" width="361">
 
−
<p>All</p>
 
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</td>
 
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</tr>
 
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<tr>
 
−
<td width="245">
 
−
<p>River type implemented</p>
 
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</td>
 
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<td colspan="2" width="361">
 
−
<p>All</p>
 
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</td>
 
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</tr>
 
−
<tr>
 
−
<td width="245">
 
−
<p>Level of certainty in effect</p>
 
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</td>
 
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<td colspan="2" width="361">
 
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<p>Very certain</p>
 
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</td>
 
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</tr>
 
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<tr>
 
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<td width="245">
 
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<p>Technology readiness level</p>
 
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</td>
 
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<td width="57">
 
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<p>TRL 9</p>
 
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</td>
 
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<td width="305">
 
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<p>actual system proven in operational environment</p>
 
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</td>
 
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</tr>
 
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</table>
 
 
[[category:Sediment measures]][[category:Measures]]
 
[[category:Sediment measures]][[category:Measures]]

Revision as of 08:22, 17 October 2019

NOTE: I don't think this is correct. Dredging is with a claw/scoop thing, this is suction.

Introduction

Changes in land-use has strongly modified the sediment yield to rivers and led to high to extreme sediment suspended load in some rivers. The exceed of fine sediment might deposit in the river, and particularly in the bed interstices, depending on the velocity and discharge in the river at the time of sediment arrival. Similarly, in some rivers, regulation has strongly reduced the flow while sediment yield has not been altered, leading to an exceed of fine sediments in the river and deposition on the bed. Therefore, fish habitat might be strongly altered and affected by an increase in water turbidity and clogging of substrate (see Chapter 5.5).

Methods, tools, and devices

During planning

Fine sediments suction induced by removal might affect spawning and larval habitats of species living in the area where removal is planned. Therefore, a control of fish species living in the area, and possibly a fish population survey, should be realized prior to any removal (Gray 2013). Site preparation for removal might also generate resuspension of sediments in the removal area and induce transport of significant sediment loads downstream the site accompanied with peaks of turbidity. Access to the river bank and adapted movements around the removal site are simple measures to integrate to the overall planning of fine sediments dredging.

During implementation

The equipment for sediment removal is a pump. The capacity of the pump is determined by the amount of water to pump, the sediment quantities to be removed and the location of water and sediment releases.

During operation

Fine sediment removal induces disturbing of sediments that will be mostly pumped and released out of the stream. However, some of the remobilized sediments might be transported further downstream and induce an increase of water turbidity and possibly re-deposition at another location. Water clarity, as well as measurement of suspended sediment concentration is recommended to evaluate the possible effects of the removal.

Classification table

Classification Selection
Fish species for the measure All
Does the measure require loss of power production -
-
Structural (requires no additional flow release)
Recurrence of maintenance Irregular at events
Which life-stage of fish is measure aimed at Spawning / Recruitment
Juvenile habitat (0+)
Juvenile habitat (1+)
Juvenile habitat (older than 1+)
Adult fish
Movements of migration of fish
Which physical parameter is mitigated -
-
Substrate and hyporheic zone
-
-
-
-
Hydropower type the measure is suitable for Plant in dam
Plant with bypass section
Dam height (m) the measure is suitable for All
Section in the regulated system measure is designed for Upstream of hydropower plant
Bypass section
Downstream outlet
River type implemented Steep gradient (up to 0.4 %)
Fairly steep with rocks, boulders (from 0.4 to 0.05 %)
Slow flowing, lowland, sandy (less than 0.05 %)
Level of certainty in effect Very certain
Technology readiness level TRL 9: actual system proven in operational environment
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