GEOMORPHIC ASSESSMENT OF CHANNEL SYSTEMS
The previous chapter introduced the concepts of fluvial geomorphology and river
mechanics. In this chapter we discuss the tools used in conducting a geomorphic assessment
of a channel system. Often users will focus on the particular streambank which is eroding their
land, or threatening a building or some piece of valuable infrastructure, and may be tempted
to ignore the processes that are occurring both upstream and downstream of the project site.
However, we must always remember that the streambank is part of a watershed system that
may have a number of interrelated problems that require an integrated solution. Adopting a
narrowly focused approach may seem efficient and may even save money in the short term,
but may lead to problems in the long term.
3.1 GEOMORPHIC ASSESSMENT OF THE SYSTEM
The geomorphic assessment provides the process-based framework to define past and
present watershed dynamics, develop integrated solutions, and assess the consequences of
remedial actions such as bank stabilization measures. This is an essential part of the design
process whether you are planning bank protection for a single streambank, or are attempting
to develop a comprehensive plan for an entire watershed. A geomorphic assessment may be
divided into the following three components: (1) data assembly; (2) field investigation; and
(3) channel stability assessment.
3.1.1 DATA ASSEMBLY
The first step in the geomorphic assessment is the gathering and compilation of
existing data. The use of historical data enables the identification of trends and provides
useful information on rates of change in the watershed. The types of information that should
be gathered depend upon the project objectives and types of problems in the watershed.
Typical relevant data includes: channel and reservoir surveys, flood history, watershed
workplans from the NRCS or other government agencies, bridge plans and surveys,
watershed erosion information, geological data, drainage district records, land use records,
historical sediment yield information, and aerial photography. This list is not exhaustive, but