Vegetation-Erosion Dynamics - River Dynamics and Integrated River Management - page 112

Fig. 2.57 Botanical evidence of events of bank cross section widening of a degraded channel. Bank forms are
indicated on the right (after Hupp, 1987)
However, much of this integrated research has remained in more academic circles rather than reaching
the applied sector, excepting some excellent biotechnical approaches to streambank stabilization. Several
directions for future applied and basic research should be fruitful; a few are now offered. Dendrogeomorphic
approaches to assessing the impact and long-term effects of channel incision offer a relatively inexpensive,
yet relatively accurate methodology that has yet to come into widespread use. The effect vegetation has
on bank stability (root strength versus surcharge) has received little quantitative study. The role vegetation
plays in affecting channel roughness, flow velocity, and sediment deposition rate and location has only
recently been appreciated and there are yet but few quantitative studies.
Review Questions
1. Answer the following questions
(a) What are main agents of erosion?
(b) Why grain erosion became important after a great earthquake?
(c) What are the ecological functions of vegetation? What are the major stresses on vegetation?
(d) Why is erosion a special stress? How are the ecological stresses classified? List the vigor stresses
and mortality stresses.
(e) What will happen if a vigor stress acts on the vegetation?
(f) What is vulnerable vegetation? Give an example.
(g) What does vegetation-erosion dynamics study and what problems can be solved with knowledge of
the dynamics?
(h) What is riparian vegetation? How does riparian vegetation affect fluvial geomorphology?
(i) State the process of degradation and recovery of streams with woody riparian vegetation and the
general variation of the vegetation, including number of species, cover, and age of the vegetation in the
process.
(j) What is dendrogeomorphology? What are the basic types of botanical evidence used in the
dendrogeomorphology?
(k) A bank failure occurred about 3-5 years ago, explain how can you estimate the accurate time of the
bank failure with the dendrogeomorphic approaches.