Channelization projects are undertaken in order to increase flow depths for navigation or/and reduce flooding, by increasing the overall conveyance capacity, reducing friction and confining the flows into one single channel. This can be accomplished by straightening, widening, deepening, realigning or/and revetting (lining) the channel. Large wood pieces embedded in the river bottom cause localized backwater that leads to sediment accumulation, bar creation and subsequent vegetative growth. Removal of such material considerably changes water flow and sediment deposition patterns and is used as a channelization technique.

Channelization simplifies the form of the channel and floodplain environment by straightening and homogenizing the channel and disconnecting it from side channel features. Channelized streams are not only straightened, which increases their slope, but their roughness is also decreased, which causes water to flow more rapidly and there is increased scour. The net effect is flood alleviation in one area at the expense of aggravated flooding in the reaches located farther downstream.

Channelization has negative consequences for the environment. The flood conveyance benefits of channelization are often offset by ecological losses resulting from increased velocities and reduced habitat diversity. Channelization eliminates bars and riffle and pool complexes needed at different times in the life cycle of certain aquatic organisms. In-stream modifications, such as a uniform cross-section and revetting, result in fewer habitats for organisms living in or on stream sediments. Hardening the banks of a river, through the use of rip-rap or concrete, can result in increased downward scour of the riverbed during high flows. In order to mitigate the negative consequences, it is important to make use of techniques such as soft revetments, soil bioengineering, porous pavements, grassy swales, etc. Revetting and supporting riverbanks without the use of concrete (spiling, mattressing, the use of geo-textiles etc.) may partially preserve some functions of the fluvial ecosystem. (WMO 2006a)