Selection and Design of Channel Rehabilitation Methods
Although there is very little guidance available for establishing the suitability of a particular technique
for a particular site condition, the designer should make the selection within the framework of three criteria:
Effectiveness of the alternative;
Environmental considerations; and
Economic factors.
Many techniques can be designed to adequately solve a specific bank stability problem by resisting
erosive forces and geotechnical failure. The challenge to an engineer is to determine the most effective
solutions to a specific problem, by recognizing which technique matches strength of protection against
strength of attack, and which therefore performs most efficiently when tested by the strongest process of
erosion and most critical mechanism of failure. Environmental and economic factors are integrated into the
selection procedure, but the chosen solution must first fulfill the requirement of being effective as bank
stabilization, otherwise environmental and economic attributes will be irrelevant.
6.1.1
SURFACE ARMOR
Armor is a protective material in direct contact with the streambank. It must have sufficient weight
and/or strength to remain in place when subjected to hydraulic forces and impact from objects carried by
the stream. It must also prevent significant loss of bank material from under the armor due to turbulence
of flow or movement of groundwater.
Armor is often simply called revetment, but the more specific term armor is used here because other
forms of bank stabilization, such as retards and retaining walls, are also referred to in some regions as
revetments.
Armor materials can be categorized as follows:
Stone;
Other self-adjusting armor;
Rigid armor; and
Flexible mattress.
Armor protection requires careful consideration of the geotechnical stability of the bank, and
sometimes a granular or fabric underlayment is required for proper interior drainage of the bank material,
or to prevent loss of fine grained material through the armor.
6.1.1.1 Stone Armor
Stone armor is the most commonly used type of armor protection. There are many variations in
the design of stone armors. The riprap blanket is the most recognizable form of stone armor. It is often
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