Difference between revisions of "Impoundment"
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04. Morphological alterations | 04. Morphological alterations | ||
==General description== | ==General description== | ||
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| + | Any transverse barrier to the flow in a river impounds water upstream. When this barrier is small (e.g. less than 10 m high) it may be called a weir, dike or small dam. Barriers that are taller than 15 m are all termed dams. All of these barriers are used for retaining water for many purposes and the river is transformed into an impoundment upstream. | ||
| + | Natural flow velocity is reduced due to the presence of the impoundment, resulting in the deposition of transported sediments. The effectiveness of a reservoir as a sediment trap is mainly dependent upon its storage capacity and the length of time that it stores water (Brune, 1953<ref><ref>Brune, G.M., 1953. Trap efficiency of Reservoirs. Transactions American Geophysical Union 34: 407–419.</ref></ref>), but even the smallest reservoirs are likely to trap most sand sized and finer particles, and large reservoirs are likely to trap close to 100% of transported mineral sediment particles. | ||
==Effect/Impact on (including literature citations)== | ==Effect/Impact on (including literature citations)== | ||
Revision as of 17:28, 16 February 2015
Contents
Impoundment
04. Morphological alterations
General description
Any transverse barrier to the flow in a river impounds water upstream. When this barrier is small (e.g. less than 10 m high) it may be called a weir, dike or small dam. Barriers that are taller than 15 m are all termed dams. All of these barriers are used for retaining water for many purposes and the river is transformed into an impoundment upstream.
Natural flow velocity is reduced due to the presence of the impoundment, resulting in the deposition of transported sediments. The effectiveness of a reservoir as a sediment trap is mainly dependent upon its storage capacity and the length of time that it stores water (Brune, 1953Cite error: Closing </ref> missing for <ref> tag</ref>), but even the smallest reservoirs are likely to trap most sand sized and finer particles, and large reservoirs are likely to trap close to 100% of transported mineral sediment particles.
Effect/Impact on (including literature citations)
- HYMO (general and specified per HYMO element)
- physico - chemical parameters
- Biota (general and specified per Biological quality elements)
Case studies where this pressure is present
- Fovant_-_Demonstrating_strategic_restoration_and_management_STREAM_(LIFE05_NAT/UK/000143)
- Klebach_-_Side_channel
- Popina
- Bakenhof_-_Dyke_relocation
- Bouxweerd
- River_Wensum_Rehabilitation_Project
- Asseltse_Plassen_-_Bank_erosion
- Rijkelse_Beemden_-_River_bed_widening
- Babina
- Chilhampton_-_Demonstrating_strategic_restoration_and_management_STREAM_(LIFE05_NAT/UK/000143)
- Buiten_Ooij_-_Sluice_operation_
- Narew_river_restoration_project_
- Lower_Traun
- Middle_Warta_River_Valley
- Heltondale_Beck_Flow_restoration
- Drava_-_Kleblach
- KUIVAJOKI
- Emån_-_Emsfors
Possible restoration, rehabilitation and mitigation measures
- Reduce undesired sediment input
- Improve continuity of sediment transport
- Manage dams for sediment flow
- Ensure minimum flows
- Establish environmental flows / naturalise flow regimes
- Increase flood frequency and duration in riparian zones or floodplains
- Shorten the length of impounded reaches
- Remove barrier
- Manage sluice and weir operation for fish migration
- Remove sediments
- Retain floodwater
- Improve backwaters
- Isolation of water bodies
