3
duction of all other ecosystem services (De Groot et al. 2002; MEA 2005). Examples
of supporting ecosystem services from rivers include primary production by plants
in the channel and floodplain and nutrient recycling by microbial organisms and
macroinvertebrates inhabiting the channel and floodplain. Cultural ecosystem services describe the non-material benefits that people derive from ecosystems: who
among us does not enjoy spending time along a river?
Diverse groups of people perceive rivers differently. This can be illustrated in an
academic context by simple generalizations about traditional engineering, geomorphic, and ecologic perceptions of rivers (Fig. 1.1; Table 1.1). A traditional engineering disciplinary perspective is likely to focus on how water flowing down a river
channel interacts with the channel boundaries to create a distribution of hydraulic
force that can modify the channel in ways that may be undesirable for those seeking
to use the channel for navigation or to limit bank erosion or overbank flooding. The
ideal river from a traditional engineering perspective is one that remains stable,
without substantially incising its banks, eroding its bed, accumulating sediment
within the channel, or flooding out of the channel. Engineering emphasizes using
mathematical relations to predict the channel form best suited to create this stability.
Engineers also design channel modifications such as bank protection or instream
structures to promote channel stability. Equations describing water flow in an open
channel and the mechanics of sediment transport provide the foundation for engineering understanding of rivers.
A geomorphic disciplinary focus is more likely to start with how interactions
across the drainage basin influence water and sediment entering the river network.
Geomorphic investigations also emphasize how channel form and process result
from interactions among water and sediment within the channel, the erosional resistance of the channel boundary, and the stability of relative base level. Geomorphic
investigations of rivers include how these diverse interactions occur across differing
scales of time and space. Qualitative and quantitative conceptual models of equilibrium and nonlinear dynamics that describe river process and form provide the foundation for geomorphic understanding of rivers.
An ecological perspective of rivers is most likely to focus on how interactions
between abiotic factors and biota create fluxes of matter and energy, as well as structuring biotic communities. As with geomorphic investigations of rivers, ecological
investigations examine processes and biotic communities across diverse scales of
space and time, from entire ecoregions and drainage basins over hundreds to thousands of years, to channel units such as pools and rivers and nutrient uptake at
minutes to hours. Conceptual models of longitudinal and lateral patterns of matter
and energy fluxes and communities (Fig. 1.1) provide the foundation for ecological
understanding of rivers.
None of these disciplinary perceptions of rivers is more correct than the others.
They differ in their relative emphases, but they also share many areas of common
interest. Ecologists can argue that their perceptions of rivers are the most comprehensive, because they include and build on understanding derived from engineering
hydrology and hydraulics and geosciences temporal and spatial scales, but also
1.1 Perceptions of Rivers
duction of all other ecosystem services (De Groot et al. 2002; MEA 2005). Examples
of supporting ecosystem services from rivers include primary production by plants
in the channel and floodplain and nutrient recycling by microbial organisms and
macroinvertebrates inhabiting the channel and floodplain. Cultural ecosystem services describe the non-material benefits that people derive from ecosystems: who
among us does not enjoy spending time along a river?
Diverse groups of people perceive rivers differently. This can be illustrated in an
academic context by simple generalizations about traditional engineering, geomorphic, and ecologic perceptions of rivers (Fig. 1.1; Table 1.1). A traditional engineering disciplinary perspective is likely to focus on how water flowing down a river
channel interacts with the channel boundaries to create a distribution of hydraulic
force that can modify the channel in ways that may be undesirable for those seeking
to use the channel for navigation or to limit bank erosion or overbank flooding. The
ideal river from a traditional engineering perspective is one that remains stable,
without substantially incising its banks, eroding its bed, accumulating sediment
within the channel, or flooding out of the channel. Engineering emphasizes using
mathematical relations to predict the channel form best suited to create this stability.
Engineers also design channel modifications such as bank protection or instream
structures to promote channel stability. Equations describing water flow in an open
channel and the mechanics of sediment transport provide the foundation for engineering understanding of rivers.
A geomorphic disciplinary focus is more likely to start with how interactions
across the drainage basin influence water and sediment entering the river network.
Geomorphic investigations also emphasize how channel form and process result
from interactions among water and sediment within the channel, the erosional resistance of the channel boundary, and the stability of relative base level. Geomorphic
investigations of rivers include how these diverse interactions occur across differing
scales of time and space. Qualitative and quantitative conceptual models of equilibrium and nonlinear dynamics that describe river process and form provide the foundation for geomorphic understanding of rivers.
An ecological perspective of rivers is most likely to focus on how interactions
between abiotic factors and biota create fluxes of matter and energy, as well as structuring biotic communities. As with geomorphic investigations of rivers, ecological
investigations examine processes and biotic communities across diverse scales of
space and time, from entire ecoregions and drainage basins over hundreds to thousands of years, to channel units such as pools and rivers and nutrient uptake at
minutes to hours. Conceptual models of longitudinal and lateral patterns of matter
and energy fluxes and communities (Fig. 1.1) provide the foundation for ecological
understanding of rivers.
None of these disciplinary perceptions of rivers is more correct than the others.
They differ in their relative emphases, but they also share many areas of common
interest. Ecologists can argue that their perceptions of rivers are the most comprehensive, because they include and build on understanding derived from engineering
hydrology and hydraulics and geosciences temporal and spatial scales, but also
1.1 Perceptions of Rivers