Term 2 Geography Term 2 Geography ProjectProject

River Channel ManagementRiver Channel Management

River Channel ManagementRiver Channel Management

There are many strategies for River There are many strategies for River Channel Management.Channel Management.

Such strategies are River Channelisation, Such strategies are River Channelisation, River Re-Sectioning, Vegetation Planting River Re-Sectioning, Vegetation Planting and Clearance, and Bank Protection.and Clearance, and Bank Protection.

River ChannelisationRiver Channelisation It involves the alteration of the river channel.It involves the alteration of the river channel. It also increases the speed of flow of the river in It also increases the speed of flow of the river in

order to prevent the water from reaching flood order to prevent the water from reaching flood height.height.

River Channelisation can be done by clearing River Channelisation can be done by clearing obstacles such as boulders or hard rocks which obstacles such as boulders or hard rocks which are protruding from the banks.are protruding from the banks.

Or deepening and widening the channel by Or deepening and widening the channel by dredging.dredging.

It is an effective long-term measure, but a lot of It is an effective long-term measure, but a lot of manpower and resources are required to carry it manpower and resources are required to carry it out.out.

River Re-SectioningRiver Re-Sectioning A river is straightened or re-sectioned, usually A river is straightened or re-sectioned, usually

along a pronounced meander through the along a pronounced meander through the creation of artificial cut-offs.creation of artificial cut-offs.

Re-Sectioning leads to the shortening of the Re-Sectioning leads to the shortening of the river, and this will increase the speed of flow.river, and this will increase the speed of flow.

Like River Channelisation, it is also an effective Like River Channelisation, it is also an effective long-term measure, but a lot of manpower and long-term measure, but a lot of manpower and resources are required to carry it out.resources are required to carry it out.

Vegetation PlantingVegetation Planting

Due to the planting of Due to the planting of vegetation, the roots of vegetation, the roots of the trees and plants can the trees and plants can help to bind the soil help to bind the soil together and stabilise the together and stabilise the river banks.river banks.

Planting of vegetation is Planting of vegetation is used to slow down the used to slow down the flow of the river.flow of the river.

Vegetation ClearanceVegetation Clearance

The clearance of vegetation refers to the trimming or The clearance of vegetation refers to the trimming or removal of vegetation along the river banks or the river removal of vegetation along the river banks or the river bed.bed.

Vegetation Clearance is often conducted to improve the Vegetation Clearance is often conducted to improve the speed of flow and stabilise the river channel.speed of flow and stabilise the river channel.

The weight of vegetation could add to bank stresses and The weight of vegetation could add to bank stresses and cause the collapse of the banks.cause the collapse of the banks.

The Vegetation may also contribute woody debris to the The Vegetation may also contribute woody debris to the river which may deflect the flow of water and accelerate river which may deflect the flow of water and accelerate bank erosion.bank erosion.

The accumulation of such debris will also slow down the The accumulation of such debris will also slow down the flow of water and encourage flooding.flow of water and encourage flooding.

Bank ProtectionBank Protection River banks can be protected by constructing River banks can be protected by constructing

artificial levees, dykes or embankments.artificial levees, dykes or embankments. They are useful in preventing the river banks They are useful in preventing the river banks

from collapsing during heavy rain, when the from collapsing during heavy rain, when the volume of flow increases dramatically.volume of flow increases dramatically.

Mississippi RiverMississippi River A series of 29 locks and dams on the upper Mississippi, most of A series of 29 locks and dams on the upper Mississippi, most of

which were built in the 1930s, is designed primarily to maintain a 9 ft which were built in the 1930s, is designed primarily to maintain a 9 ft (2.7 m) deep channel for commercial barge traffic. (2.7 m) deep channel for commercial barge traffic.

The dams make the river deeper and wider but do not stop it. No The dams make the river deeper and wider but do not stop it. No flood control is intended.flood control is intended.

Mississippi RiverMississippi River There are two major obstacles on the upper Mississippi, the Des There are two major obstacles on the upper Mississippi, the Des

Moines Rapids and the Rock Island Rapids, where the river was Moines Rapids and the Rock Island Rapids, where the river was shallow and the riverbed was rock. The Corps recommended shallow and the riverbed was rock. The Corps recommended excavation of a 5 ft (1.5 m) deep channel at the Des Moines Rapids, excavation of a 5 ft (1.5 m) deep channel at the Des Moines Rapids, but work did not begin until after Lieutenant Robert E. Lee endorsed but work did not begin until after Lieutenant Robert E. Lee endorsed the project in 1837. The Corps later also began excavating the Rock the project in 1837. The Corps later also began excavating the Rock Island Rapids.Island Rapids.

By 1866, it had become evident that excavation was impractical, By 1866, it had become evident that excavation was impractical, and it was decided to build a canal around the Des Moines Rapids. and it was decided to build a canal around the Des Moines Rapids. The canal opened in 1877, but the Rock Island Rapids remained an The canal opened in 1877, but the Rock Island Rapids remained an obstacle.obstacle.

Mississippi RiverMississippi River In 1878, Congress authorized the Corps to establish a 4.5 ft (1.4 m) In 1878, Congress authorized the Corps to establish a 4.5 ft (1.4 m)

deep channel to be obtained by building wing dams which direct the deep channel to be obtained by building wing dams which direct the river to a narrow channel causing it to cut a deeper channel, by river to a narrow channel causing it to cut a deeper channel, by closing secondary channels and by dredging.closing secondary channels and by dredging.

To improve navigation between St. Paul, Minnesota, and Prairie du To improve navigation between St. Paul, Minnesota, and Prairie du Chien, Wisconsin, the Corps constructed several dams on lakes in Chien, Wisconsin, the Corps constructed several dams on lakes in the headwaters area, including Lake Winnibigoshish and Lake the headwaters area, including Lake Winnibigoshish and Lake Pokegama. The dams, which were built beginning in the 1880s, Pokegama. The dams, which were built beginning in the 1880s, stored spring run-off which was released during low water to help stored spring run-off which was released during low water to help maintain channel depth.maintain channel depth.

Prior to the 1927 flood, the Corps' primary strategy was to close off Prior to the 1927 flood, the Corps' primary strategy was to close off as many side channels as possible to increase the flow in the main as many side channels as possible to increase the flow in the main river. It was thought that the river's velocity would scour off bottom river. It was thought that the river's velocity would scour off bottom sediments, deepening the river and decreasing the possibility of sediments, deepening the river and decreasing the possibility of flooding.flooding.

Mississippi RiverMississippi River

The Corps now actively creates The Corps now actively creates floodways to divert periodic water floodways to divert periodic water surges into backwater channels and surges into backwater channels and lakes. lakes.

The Old River Control structure also The Old River Control structure also serve as a major floodgates that can serve as a major floodgates that can be opened to prevent flooding. Some be opened to prevent flooding. Some of the pre-1927 strategy is still in use of the pre-1927 strategy is still in use today, the Corps actively cuts the today, the Corps actively cuts the necks of horseshoe bends, allowing necks of horseshoe bends, allowing the water to move faster and reducing the water to move faster and reducing flood heights.flood heights.

The Old River Control Structure