Mountain Rivers and Incised Channels - River Dynamics and Integrated River Management - page 161

Obviously, many of the effects listed are closely related, and others might choose to organize them
differently, but the review presented here should provide a systematic overview of the environmental
effects of channel incision.

(a) (b)
Fig. 3.44 (a) Incised upper Jiangjia Ravine; (b) Bank failures and landslides destroyed the pine forest at the upper
end of the Jiangjia Ravine (See color figure at the end of this topic)

Table 3.6 Review of environmental, ecological, and societal impacts of channel incision (after Bravard et al., 1999)
Effects on channel
geometry, structures, and
riparian vegetation

Environmental, ecological, and
societal impacts

Location and references

Narrowing of active
channel, decreased
width/depth ratio

Reduced area of aquatic habitat
and altered channel margin habitat;
Reduced bed surface for
infiltration and groundwater
recharge. Concentration of flow
and increased shear stress lead to
further incision

Bear River, California (James, 1991); Cache
Creek, California (Northwest Hydraulics
consultants, 1995); Southeast France (Bravard et
al., 1997)

Channel simplification and
abandonment of multiple
channels

Loss of habitat diversity.
Impoverishment of fish community.
Reduced length of channel margin
habitat

northern Mississippi (Shields et al., 1994)

Modification of bank
morphology

Bank erosion and subsequent
channel widening and instability,
loss of agricultural land, and
infrastructure. Change in bank
configuration reduces opportunity
for seedling establishment
downstream.

northern Mississippi (Thorne, 1997)
Iowa (Lohnes, 1997);
Marias River, Montana (Rood and Mahoney,
1995)

Increased sediment
transport to downstream
from erosion of bed and
banks

Aggradation of downstream
reaches

Wooler Water, UK (Sear and Archer, 1998)

Loss of gravel bars Loss of habitat, reduced

biodiversity

Isar and Lech Rivers, Bavaria, Germany (Reich,
1991, 1994)

Armoring (coarsening of
substrate)

Loss of spawning gravels for fish Sacramento River, California (Parfitt and Buer,

1980); Garonne River, France (Beaudelin, 1989)

Exposure of bedrock Loss of spawning gravels and

hyporheic habitats, Loss of
groundwater, Barrier to fish
migration

Ardeche and Dr6me Rivers (Landon and Piegay,
1994)