69
to limit property loss or hazards associated with channel movement. Channelization
is yet another form of channel engineering, which involves widening, deepening,
and straightening the channel, but also blocking the entrance to secondary channels.
Finally, removal of instream and bank large wood is a form of channel engineering.
These activities have most commonly been undertaken to limit overbank flooding
and the duration of flooding; to enhance navigation; and to limit channel erosion of
the floodplain (DuPont 1925; Gillette 1972; Landwehr and Rhoads 2003;
Hohensinner et  al. 2004). Channelization has also sometimes been conducted to
enhance fish passage or to make the channel more esthetically attractive.
Records of activities such as bank stabilization and large wood removal go back
centuries in Eurasia (Comiti 2012) and North America (Wohl 2014). In the United
States, for example, the national government removed at least 1.5 million pieces of
Fig. 3.5 Schematic illustration of cascade of effects on channel form, complexity, connectivity,
retention, and biodiversity as a result of channelization. Upper photo shows a diverse, natural river
in the Brooks Range of Alaska, USA. Lower photo shows a portion of the Cache la Poudre River,
Colorado, USA that was channelized during the 1960s; photograph was taken 50  years after
channelization
3.2 Direct Alterations of River Networks and River Corridors