River Ecology and Restoration - River Dynamics and Integrated River Management - page 699

conjunction with stone to provide bank protection as well as improved aquatic habitat cut into the bank,
such that the root wads extend beyond the bank face at the toe (Fig. 10.53). The logs are overlapped
and/or braced with stone to ensure stability, and the protruding rootwads effectively reduce flow
velocities at the toe and over a range of flow elevations (Fig. 10.54). A major advantage of this approach
is that it reestablishes one of the natural functions of large woody debris in streams by creating a
dynamic near-bank environment that traps organic material and provides colonization substrates for
invertebrates and refuge habitat for fish. The logs eventually rot, resulting in a more natural bank. The
revetment stabilizes the bank until woody vegetation has matured, at which time the channel can return
to a more natural pattern.

Existing vegetation, plantings
or soil bioengineering syste m s

2.5-3.5 m

Rootwad
Baseflow
Strea m be d

Thalweg channel

Diameter of log
0.6 m.

Boulder 1.5 times
diameter of log

Footer log

Fig. 10.53 Large trees and stone are used to provide bank protection (after FISRWG, 1997)

Fig. 10.54 The protruding rootwads effectively reduce flow velocities at the toe (after FISRWG, 1997)

10.4.4 Artificial Wetlands
Artificial wetlands have been created for ecological restoration. Wetland-loss has become a problem in
many river systems as a result of sediment reduction, railway and highway construction, and drainage
system development. The floral communities and faunal communities in the wetlands suffer from
development and wetland-loss. To restore the wetland ecology artificial wetlands, for instance green tree