61
Table 3.2 Direct alterations of river corridors
Alteration
Effects
Sample references
Channel engineering
Dredging
Bank stabilization
Channelization
Wood removal
Decreased hydraulic resistance;
increased downstream conveyance
and flow velocity; decreased
complexity, lateral and vertical
connectivity, and retention; bed
coarsening and channel incision
Scarnecchia (1988), Rhoads
(1990), Kesel and Yodis
(1992), Wyzga (2001) and
Hohensinner et al. (2004)
Placer and aggregate
mining
Altered channel geometry and
stability; increased sediment transport
Knighton (1989), Hilmes and
Wohl (1995) and Lawrence
and Davies (2014)
Beaver trapping
Decreased hydraulic resistance;
increased downstream conveyance
and flow velocity; decreased
complexity, lateral and vertical
connectivity, and retention
Pollock et al. (2003, 2007,
2014), Green and Westbrook
(2009) and Polvi and Wohl
(2012, 2014)
Log floating
Simplified, enlarged channel cross
sectional area; decreased hydraulic
resistance; increased downstream
conveyance and flow velocity;
decreased complexity, lateral and
vertical connectivity, and retention
Young et al. (1994), Törnlund
and Östlund (2002), Comiti
(2012) and Haidvogl et al.
(2015)
Floodplain drainage
Decreased complexity and retention,
particularly with respect to nutrients
Spaling and Smit (1995) and
Holden (2006)
Levee construction
Increased downstream conveyance
and flow velocity; decreased
complexity, lateral connectivity, and
retention; bed coarsening and channel
incision
Frings et al. (2009) and Czech
et al. (2015)
Floodplain
deforestation
Decreased complexity and retention;
increased bank erosion
Iwata et al. (2003)
Riparian grazing
Decreased riparian vegetation,
increased runoff and bank erosion,
wider channel cross section
Trimble and Mendel (1995)
Flow regulation
Altered hydrograph, transport
capacity, water chemistry,
connectivity
Ligon et al. (1995), Magilligan
and Nislow (2001), Poff et al.
(2007) and Kondolf et al.
(2014)
Introduced species
Variable, depending on extent and
type of species, but include altered
hydraulic and bank resistance, and
altered sediment transport, and
nutrient and LW availability
Graf (1978) and Ulloa et al.
(2011)
Commercial
extinction of species
(fish, mussels, etc)
Changes in river trophic cascades,
primary production, and suspended
sediment
Strayer et al. (1999, 2004)
3.1 Indirect Alterations of River Networks and River Corridors
Table 3.2 Direct alterations of river corridors
Alteration
Effects
Sample references
Channel engineering
Dredging
Bank stabilization
Channelization
Wood removal
Decreased hydraulic resistance;
increased downstream conveyance
and flow velocity; decreased
complexity, lateral and vertical
connectivity, and retention; bed
coarsening and channel incision
Scarnecchia (1988), Rhoads
(1990), Kesel and Yodis
(1992), Wyzga (2001) and
Hohensinner et al. (2004)
Placer and aggregate
mining
Altered channel geometry and
stability; increased sediment transport
Knighton (1989), Hilmes and
Wohl (1995) and Lawrence
and Davies (2014)
Beaver trapping
Decreased hydraulic resistance;
increased downstream conveyance
and flow velocity; decreased
complexity, lateral and vertical
connectivity, and retention
Pollock et al. (2003, 2007,
2014), Green and Westbrook
(2009) and Polvi and Wohl
(2012, 2014)
Log floating
Simplified, enlarged channel cross
sectional area; decreased hydraulic
resistance; increased downstream
conveyance and flow velocity;
decreased complexity, lateral and
vertical connectivity, and retention
Young et al. (1994), Törnlund
and Östlund (2002), Comiti
(2012) and Haidvogl et al.
(2015)
Floodplain drainage
Decreased complexity and retention,
particularly with respect to nutrients
Spaling and Smit (1995) and
Holden (2006)
Levee construction
Increased downstream conveyance
and flow velocity; decreased
complexity, lateral connectivity, and
retention; bed coarsening and channel
incision
Frings et al. (2009) and Czech
et al. (2015)
Floodplain
deforestation
Decreased complexity and retention;
increased bank erosion
Iwata et al. (2003)
Riparian grazing
Decreased riparian vegetation,
increased runoff and bank erosion,
wider channel cross section
Trimble and Mendel (1995)
Flow regulation
Altered hydrograph, transport
capacity, water chemistry,
connectivity
Ligon et al. (1995), Magilligan
and Nislow (2001), Poff et al.
(2007) and Kondolf et al.
(2014)
Introduced species
Variable, depending on extent and
type of species, but include altered
hydraulic and bank resistance, and
altered sediment transport, and
nutrient and LW availability
Graf (1978) and Ulloa et al.
(2011)
Commercial
extinction of species
(fish, mussels, etc)
Changes in river trophic cascades,
primary production, and suspended
sediment
Strayer et al. (1999, 2004)
3.1 Indirect Alterations of River Networks and River Corridors