Chapter 6: Management Measures for Hydromodification: Channelization and Channel Modification, Dams, and Streambank and Shoreline Erosion Page: 3 of 110
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IL. CHANNELIZATION AND CHANNEL MODIFICATION
One form of hydromodification is channelization or channel modification. These terms (used interchangeably)
describe river and stream channel engineering undertaken for the purpose of flood control, navigation, drainage
improvement, and reduction of channel migration potential (Brookes, 1990). Activities such as straightening,
widening, deepening, or relocating existing stream channels and clearing or snagging operations fall into this
category. These forms of hydromodification typically result in more uniform channel cross sections, steeper stream
gradients, and reduced average pool depths.
The terms channelization and channel modification are also used in this chapter to refer to the excavation of borrow
pits, canals, underwater mining, or other practices that change the depth, width, or location of waterways or
embayments in coastal areas. Excavation of marina basins is addressed separately in Chapter 5 of this guidance.
The term flow alteration describes a category of hydromodification activities that result in either an increase or a
decrease in the usual supply of fresh water to a stream, river, or estuary. Flow alterations include diversions,
withdrawals, and impoundments. In rivers and streams, flow alteration can also result from undersized culverts,
transportation embankments, tide gates, sluice gates, and weirs.
Levees along a stream or river channel are also addressed by this section. A levee is defined by the U.S. Army
Corps of Engineers (USACE) as an embankment or shaped mound for flood control or hurricane protection (USACE,
1981). Pond banks, and other small impoundment structures, often referred to as levees in the literature, are not
considered to be levees as defined in this section. Additionally, a dike is not used in this guidance to refer to the
same structure as a levee, but rather is defined as a channel stabilization structure sited in a river or stream
perpendicular to the bank.
For the purpose of this guidance, no distinction will be made between the terms river and stream because no
definition of either could be found to quantitatively distinguish between the two. Likewise, no distinction will be
made for word combinations of these two terms; for example, streambank and riverbank will be, considered to be
The following definitions for common terms associated with channelization activities apply to this chapter (USACE,
1983). Other definitions are provided in the Glossary at the end of the chapter.
Channel: A natural or constructed waterway that continuously or periodically passes water,
Channel stabilization: Structures placed below the elevation of the average surface water level (lower bank)
to control bank erosion or to prevent bank or channel failure.
Streambank: The side slopes of a channel between which the streamflow is normally confined.
Lower bank: The portion of the streambank below the elevation of the average water level of the stream.
Upper bank: The portion of the streambank above the elevation of the average water level of the stream.
Streambank stabilization: Structures placed on or near a distressed streambank to control bank erosion or to
prevent bank failure.
Based on the above definitions, the difference between channel stabilization and streambank stabilization is that in
streambank stabilization, the upper bank is also protected from erosion or failure. This additional protection guards
against erosive forces caused by high-water events and by land-based causes such as runoff or improper siting of
ll. Channelization and Channel Modification
EPA-840-B-92-002 January 1993
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United States. Environmental Protection Agency. Chapter 6: Management Measures for Hydromodification: Channelization and Channel Modification, Dams, and Streambank and Shoreline Erosion, chapter, January 1993; (digital.library.unt.edu/ark:/67531/metadc948721/m1/3/: accessed February 23, 2019), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.