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The Effects of Channelization

Overview. Types of ChannelizationHistoryMorphological EffectsBiological Impacts. Types of Channelization. Definition ? includes ?all processes of river engineering for the purposes of flood control, drainage improvement, maintenance of navigation, reduction of bank erosion ot relocation for highw

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The Effects of Channelization

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    1. The Effects of Channelization Christin Cruz

    2. Overview Types of Channelization History Morphological Effects Biological Impacts

    3. Types of Channelization Definition – includes “all processes of river engineering for the purposes of flood control, drainage improvement, maintenance of navigation, reduction of bank erosion ot relocation for highway construction” (Brookes, 1988).

    4. History Long history – Yellow River, China, 600 BC Most prolific in developed countries In past 150 years in the US 320,000 km of river modified (reference: Mississippi is 3,705 km) as of 1988 Denmark – almost 100% of drainage network has been modified

    5. Types of Channelization Straightening Resectioning Clearing and Snagging

    6. Types of Channelization Straightening River is shortened by artificial cutoffs

    7. Types of Channelization Resectioning (widening and/or deepening) Increase capacity to reduce overbank flooding

    8. Types of Channelization Clearing and Snagging Removal of obstructions

    9. Morphological Effects

    10. Morphological Effects

    11. Morphological Effects Example Willow Drainage Ditch, Iowa Began modification in 1919 with a trapzoidal cross-section with a 1:1 side slope Gradient increase, low reaches 1.0 m/km to 1.5 m/km, upstream 1.4 m/km to 1.7 m/km Maximum increase in channel size of 440% Depth increase of 3.4 m to 13 m

    12. Morphological Effects

    13. Morphological Effects Resectioning Widening reduces stream power, reducing sed. discharge Low flows deposit sed. Because of reduced velocities Can form structures such as mid-channel bars or berms

    14. Resectioning Example: River Tame, England Reverted back to original capacity in less than 30 yrs

    15. Morphological Effects

    16. Morphological Effects Clearing and Snagging Few studies with before-and-after effects Cause bank erosion and widening of channel

    17. Biological Effects Bank cover is eliminated Pools are lost Flow approaches laminar Homogeneous substrate Habitat diversity and niche potential are reduced

    18. Biological Impacts

    19. Biological Effects Macriinvertebrate Species are confined to specific ranges of velocity Require specific a specific substrate Temperature and dissolved oxygen

    20. Biological Effects Fish Reduced habitat (lack of cover) Sediment blankets effects spawning areas Overhanging veg. effects temp. and potential food sources

    21. Biological Effects

    22. Biological Effects

    23. Conclusions Channelization has negative affects on stream morphology and organisms within the stream

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