The Effects of Channelization
Transcript of The Effects of Channelization
![Page 1: The Effects of Channelization](https://reader033.fdocuments.in/reader033/viewer/2022061202/547ad7e4b379594e2b8b4b97/html5/thumbnails/1.jpg)
The Effects of Channelization
Christin Cruz
![Page 2: The Effects of Channelization](https://reader033.fdocuments.in/reader033/viewer/2022061202/547ad7e4b379594e2b8b4b97/html5/thumbnails/2.jpg)
Overview
• Types of Channelization
• History
• Morphological Effects
• Biological Impacts
![Page 3: The Effects of Channelization](https://reader033.fdocuments.in/reader033/viewer/2022061202/547ad7e4b379594e2b8b4b97/html5/thumbnails/3.jpg)
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).
![Page 4: The Effects of Channelization](https://reader033.fdocuments.in/reader033/viewer/2022061202/547ad7e4b379594e2b8b4b97/html5/thumbnails/4.jpg)
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
![Page 5: The Effects of Channelization](https://reader033.fdocuments.in/reader033/viewer/2022061202/547ad7e4b379594e2b8b4b97/html5/thumbnails/5.jpg)
Types of Channelization
• Straightening
• Resectioning
• Clearing and Snagging
![Page 6: The Effects of Channelization](https://reader033.fdocuments.in/reader033/viewer/2022061202/547ad7e4b379594e2b8b4b97/html5/thumbnails/6.jpg)
Types of Channelization
• Straightening– River is shortened by
artificial cutoffs
Yalobusha River, Mississippi (Downs and Gregory, 2004)
![Page 7: The Effects of Channelization](https://reader033.fdocuments.in/reader033/viewer/2022061202/547ad7e4b379594e2b8b4b97/html5/thumbnails/7.jpg)
Types of Channelization
• Resectioning (widening and/or deepening)– Increase capacity to
reduce overbank flooding
(Iowa DNR website)
![Page 8: The Effects of Channelization](https://reader033.fdocuments.in/reader033/viewer/2022061202/547ad7e4b379594e2b8b4b97/html5/thumbnails/8.jpg)
Types of Channelization
• Clearing and Snagging– Removal of
obstructions
![Page 9: The Effects of Channelization](https://reader033.fdocuments.in/reader033/viewer/2022061202/547ad7e4b379594e2b8b4b97/html5/thumbnails/9.jpg)
Morphological Effects
![Page 10: The Effects of Channelization](https://reader033.fdocuments.in/reader033/viewer/2022061202/547ad7e4b379594e2b8b4b97/html5/thumbnails/10.jpg)
Morphological Effects
![Page 11: The Effects of Channelization](https://reader033.fdocuments.in/reader033/viewer/2022061202/547ad7e4b379594e2b8b4b97/html5/thumbnails/11.jpg)
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
![Page 12: The Effects of Channelization](https://reader033.fdocuments.in/reader033/viewer/2022061202/547ad7e4b379594e2b8b4b97/html5/thumbnails/12.jpg)
Morphological Effects
![Page 13: The Effects of Channelization](https://reader033.fdocuments.in/reader033/viewer/2022061202/547ad7e4b379594e2b8b4b97/html5/thumbnails/13.jpg)
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
![Page 14: The Effects of Channelization](https://reader033.fdocuments.in/reader033/viewer/2022061202/547ad7e4b379594e2b8b4b97/html5/thumbnails/14.jpg)
• Resectioning• Example:• River Tame, England• Reverted back to
original capacity in less than 30 yrs
![Page 15: The Effects of Channelization](https://reader033.fdocuments.in/reader033/viewer/2022061202/547ad7e4b379594e2b8b4b97/html5/thumbnails/15.jpg)
Morphological Effects
![Page 16: The Effects of Channelization](https://reader033.fdocuments.in/reader033/viewer/2022061202/547ad7e4b379594e2b8b4b97/html5/thumbnails/16.jpg)
Morphological Effects
• Clearing and Snagging– Few studies with before-and-after effects– Cause bank erosion and widening of channel
![Page 17: The Effects of Channelization](https://reader033.fdocuments.in/reader033/viewer/2022061202/547ad7e4b379594e2b8b4b97/html5/thumbnails/17.jpg)
Biological Effects
• Bank cover is eliminated
• Pools are lost
• Flow approaches laminar
• Homogeneous substrate
• Habitat diversity and niche potential are reduced
![Page 18: The Effects of Channelization](https://reader033.fdocuments.in/reader033/viewer/2022061202/547ad7e4b379594e2b8b4b97/html5/thumbnails/18.jpg)
Biological Impacts
![Page 19: The Effects of Channelization](https://reader033.fdocuments.in/reader033/viewer/2022061202/547ad7e4b379594e2b8b4b97/html5/thumbnails/19.jpg)
Biological Effects
• Macriinvertebrate– Species are confined to specific ranges of
velocity– Require specific a specific substrate– Temperature and dissolved oxygen
![Page 20: The Effects of Channelization](https://reader033.fdocuments.in/reader033/viewer/2022061202/547ad7e4b379594e2b8b4b97/html5/thumbnails/20.jpg)
Biological Effects
• Fish– Reduced habitat (lack of cover)– Sediment blankets effects spawning areas– Overhanging veg. effects temp. and potential
food sources
![Page 21: The Effects of Channelization](https://reader033.fdocuments.in/reader033/viewer/2022061202/547ad7e4b379594e2b8b4b97/html5/thumbnails/21.jpg)
Biological Effects
![Page 22: The Effects of Channelization](https://reader033.fdocuments.in/reader033/viewer/2022061202/547ad7e4b379594e2b8b4b97/html5/thumbnails/22.jpg)
Biological Effects
![Page 23: The Effects of Channelization](https://reader033.fdocuments.in/reader033/viewer/2022061202/547ad7e4b379594e2b8b4b97/html5/thumbnails/23.jpg)
Conclusions
• Channelization has negative affects on stream morphology and organisms within the stream