HR: 08:35h
AN: H31E-01 INVITED     [PDF]
TI: River Restoration as a Challenge to Hydrological Science
AU: * Dunne, T
EM: tdunne@bren.ucsb.edu
AF: University of California, Santa Barbara, Donald Bren School of Environmental Science and Management, Santa Barbara, CA 93106-5131 United States
AB: The readiness of affluent societies to invest resources in changing degraded rivers and floodplains to some other desired state (widely referred to as 'restoration') raises the question of how hydrological scientists might contribute their knowledge to the effort. The interdisciplinary nature of post-1990 hydrologic science makes it a promising contributor to river restoration. A central role in this effort has to be played by fluvial geomorphology, the science that explains the formation and continual evolution of channel and floodplain topography, and thus of habitat characteristics that depend on channel bed stability, flow depths and velocities, drainage conditions, and sediment textures and chemistry. Prediction of how such features develop requires understanding of sediment supplies, the effects of active tectonics and recent geologic history (such as deglaciation or sea-level rise) that influence the sediment budget of reaches, as well as the role of flow regimes, altered by catchment changes or reservoir storage. Hydrologists need to characterize flow regimes in ways that are more explicitly useful for understanding valley-floor inundation and drainage than are traditional methods developed for planning flood control and reservoir storage. They also need to develop ways of predicting future streamflow regimes, given the emerging recognition that global geophysical processes generate both persistent excursions and long-term trends away from our current streamflow paradigm of stationary, random inter-annual variability. Interactions between surface and ground waters within the subtle, complex topography and sedimentology of floodplains create habitats and affect their chemistry. The most difficult set of problems involves translating knowledge of the physics of variable form and flow conditions into quantitative understanding of habitat characteristics and their significance for biological diversity and productivity as these characteristics fluctuate through time. The increasingly interdisciplinary geophysical societies are the appropriate forums for developing the essential knowledge for restoration. This conclusion raises the question of how to motivate scientific studies of these fundamental processes, to minimize the need for trial-and-error solutions and static characterizations of each new river restoration target. Scientific studies of rivers and floodplains are rare. Widely tested prediction models for the behavior of alluvial environments and their biota are not emerging as quickly as the need arises. We have not, for example, developed an approach to anticipating the flow regimes of rivers over the next century. Predictions of catchment sediment supplies and sediment transport, including channel-floodplain exchanges rely on: concepts and calibrations from sparse, decades-old data sets; lack of modern data collection; and limited use of quantitative tools for estimating sedimentation rates. Many applications of fluvial geomorphology rely only on qualitative conceptual models of channel equilibrium, and are not sufficiently robust for predicting form changes under transient and geometrically constrained conditions. Theories of channel form and change need to be developed from thoroughly instrumented studies of flow and sediment transport in complex channels. Definition of the fundamental connections between habitat characteristics and physical processes would allow probabilistic modeling of habitat use and its long-term evolution. Through these and similar studies, a research agenda could arise to support river restoration.
DE: 1800 HYDROLOGY
SC: Hydrology [H]
MN: 2003 Fall Meeting