11
© The Author(s) 2018
E. Wohl, Sustaining River Ecosystems and Water Resources, SpringerBriefs in
Environmental Science, DOI 10.1007/978-3-319-65124-8_2
Chapter 2
Rivers as Ecosystems
This chapter reviews the different physical components of the river corridor, the
physical processes that create and maintain those components, and the interactions
between physical processes and living organisms. Among the critical aspects of
physical processes and physical-biotic interactions are transfers of matter and
energy and the occasional disturbances that reconfigure the river ecosystem and the
processes occurring within the ecosystem. Individual rivers and segments of rivers
respond differently to these disturbances and the nature of the response is characterized by how much the river ecosystem changes and how quickly the ecosystem
recovers from change.
2.1 Physical Components of the River Corridor
As noted in the first chapter, a river corridor consists of the active channel(s), a
floodplain, and the hyporheic zone. Terraces are also present along many river valleys. Terraces consist of former channel or floodplain surfaces now elevated above
contemporary flood levels as a result of continued deposition on the floodplain or
incision by the active channel (Merritts et al. 1994; Pazzaglia 2013). Because they
are above the elevation commonly reached by flood waters, terraces are not considered part of the river corridor in this discussion. Terraces, however, can strongly
influence connectivity between the river corridor and adjacent uplands (Baartman
et al. 2013).
Erosional and depositional forms created by river processes typically delineate
the active channel, which in most regions does not support mature woody vegetation (Osterkamp and Hedman 1977; Arnaud et al. 2015). Exceptions can occur
within ephemeral channels in arid regions, which may have widely spaced mature
trees within the active channel (Fig. 2.1). The upper elevation limit at which water
is contained within a channel distinguishes the active channel from adjacent
floodplain areas.
© The Author(s) 2018
E. Wohl, Sustaining River Ecosystems and Water Resources, SpringerBriefs in
Environmental Science, DOI 10.1007/978-3-319-65124-8_2
Chapter 2
Rivers as Ecosystems
This chapter reviews the different physical components of the river corridor, the
physical processes that create and maintain those components, and the interactions
between physical processes and living organisms. Among the critical aspects of
physical processes and physical-biotic interactions are transfers of matter and
energy and the occasional disturbances that reconfigure the river ecosystem and the
processes occurring within the ecosystem. Individual rivers and segments of rivers
respond differently to these disturbances and the nature of the response is characterized by how much the river ecosystem changes and how quickly the ecosystem
recovers from change.
2.1 Physical Components of the River Corridor
As noted in the first chapter, a river corridor consists of the active channel(s), a
floodplain, and the hyporheic zone. Terraces are also present along many river valleys. Terraces consist of former channel or floodplain surfaces now elevated above
contemporary flood levels as a result of continued deposition on the floodplain or
incision by the active channel (Merritts et al. 1994; Pazzaglia 2013). Because they
are above the elevation commonly reached by flood waters, terraces are not considered part of the river corridor in this discussion. Terraces, however, can strongly
influence connectivity between the river corridor and adjacent uplands (Baartman
et al. 2013).
Erosional and depositional forms created by river processes typically delineate
the active channel, which in most regions does not support mature woody vegetation (Osterkamp and Hedman 1977; Arnaud et al. 2015). Exceptions can occur
within ephemeral channels in arid regions, which may have widely spaced mature
trees within the active channel (Fig. 2.1). The upper elevation limit at which water
is contained within a channel distinguishes the active channel from adjacent
floodplain areas.