Problem Statement Habitats of most rivers of the US are perceived to be degraded as a result of human-induced stresses. This research is motivated by the high relevance of physical habitat to biotic communities and the critical nexus that physical habitat shares with river restoration and management. Habitat, in general, describes the three-dimensional structure in which organisms live (Gordon and others, 1992). Habitat can have physical, chemical, and biological components; this task is concerned primarily with physical habitat as measured by depth, velocity, and substrate, and how those components are arranged in time and space. Physical habitat in river corridors can be altered by human actions by changing flow regime or by [...]
Summary
Problem Statement
Habitats of most rivers of the US are perceived to be degraded as a result of human-induced stresses. This research is motivated by the high relevance of physical habitat to biotic communities and the critical nexus that physical habitat shares with river restoration and management.
Habitat, in general, describes the three-dimensional structure in which organisms live (Gordon and others, 1992). Habitat can have physical, chemical, and biological components; this task is concerned primarily with physical habitat as measured by depth, velocity, and substrate, and how those components are arranged in time and space.
Physical habitat in river corridors can be altered by human actions by changing flow regime or by changing channel morphology, or by changing both. In natural rivers, channel morphology is expected to be “equilibrated” to some range of flows that are responsible for the bulk of sediment transport and consequent geomorphic expression. When river discharges are altered by human actions, channel morphology and spatial and temporal distributions of habitats are changed. These changes may or may not be harmful to riverine species or intended uses of the river. In highly managed rivers, habitat can also be altered independently from flow regime by engineered structures, including bank revetments, levees, and channel-training structures. In these engineered rivers, channel morphology is independently imposed on the river, and physical habitats are not equilibrated to flow regime.
Understanding the interaction of hydrology (flow regime) and geomorphology (channel morphology) is critical for evaluating habitat loss and degradation, and for guiding river restoration designs. Where it is reasonable to neglect the effects of sediment transport, the spatial and temporal distribution of physical habitat can be modeled with operational multidimensional hydraulic models that calculate changes in habitat with changing discharge – hydrodynamic time scales. This technique is maturing, but challenges remain in the areas of optimizing model formulation (data density, calibration/verification standards, biologically meaningful model scales), defining biological significance of physical habitats, and understanding spatial and temporal patterns. More importantly, in most rivers significant sediment transport takes place and channel geometry changes over time. These geomorphic effects are poorly captured in available research models: there is a pressing need to address the coupling of geomorphic and hydrologic habitat dynamics.
When time frames are extended, a great deal of uncertainty becomes apparent because of complex geomorphic adjustments of watersheds. Natural and human-influenced disturbances are transmitted through watersheds and may diminish or grow as the travel downstream (and sometimes upstream) over time. Geomorphic adjustments are characterized by complex response: thresholds, feedbacks, and sediment-routing within watersheds result in non-linear, lagged, and unexpected cumulative changes in physical habitat. There is a pressing need to understand broad-scale, long-term geomorphic responses to evaluate resource management and restoration options. Current understanding is so poor that in many rivers there is difficulty in identifying the signal of human disturbance from among natural variation.
Objectives
The general objective of the River Corridor Habitat Dynamics project is to develop a predictive understanding of rates and processes of river corridor habitat dynamics resulting from hydrologic and geomorphic sources, and to apply this fundamental understanding to restoration and adaptive management of rivers and their floodplains. This information is critical to decisions, planning, and policies of partner agencies such as the US Fish and Wildlife Service and the US Army Corps of Engineers.
Specific objectives are:
1) Develop multi-scale understanding of the origins and transmission of physical disturbances through drainage basins, and how the disturbances affect river-corridor physical habitats.
2) Develop measurement and modeling tools and instrumentation to apply to hydrologic, hydraulic, and geomorphic assessment of habitat dynamics in river corridors ranging in size from wadeable streams to “Great Rivers”.
3) Improve understanding of short- and long-term habitat dynamics through field-scale, adaptive-management experiments.
4) Link understanding of physical habitat dynamics to biotic responses.
5) Apply understanding to adaptive management of river systems under varying environmental conditions.
Relevance to Ecosystems Mission Area and USGS programs:
The River Corridor Habitat Dynamics Project is designed to provide science information relevant to multiple USGS program goals and science themes. The research relates directly to primary Terrestrial, Freshwater, and Marine Ecosystems Program goals: (2) to devise a restoration and adaptive management framework for impaired ecosystems; and (3) to model factors controlling ecosystem patterns at various scales and develop decision support systems which integrate this information with management options. The project also supports goals of the Fisheries: Aquatic and Endangered Resources Program, in particular: 3) Quantify and describe functional relationships among aquatic species and habitats to provide information to conserve or restore aquatic community structure and function, and 5) Develop research and technology tools to provide the scientific basis for developing adaptive management strategies and evaluating their effectiveness for restoration efforts to sustain aquatic resources.
This research contributes directly to the USGS Ecosystems Mission Area as it provides fundamental research into physical and chemical processes affecting river-corridor habitat structure and function, and their resilience under changing environmental conditions. It also relates to the USGS Water Mission Area theme as it addresses how re-engineering of large river channels interacts with restoration of flow regimes to provide ecosystem services for threatened and endangered species. Similarly, understanding of the efficacy of channel re-engineering in restoring ecosystem functions will help develop options for mitigating effects of climate change (Climate and Land Use Mission Area). Finally, re-engineering of river corridors for habitat promises to decrease flood hazards by providing increased floodplain storage and by removing infrastructure from the floodplain (Hazards Mission Area). Results of this project will provide science information to address interactions between habitat enhancements and hazards reduction.
Approach
The general strategy of this project is to address physical habitat dynamics in coordinated field-based, experimental, and computational approaches. A central tenet of this strategy is to base habitat dynamics research on a well-grounded understanding of river ecology and species' needs.
Detailed approaches and methods vary by sub-task, which are developed opportunistically in response to interests and funding of collaborating agencies. Historical, stratigraphic, dendrochronologic, and photogrammetric methods are applied to develop long-term habitat datasets. Geographic information systems are used to compile water-shed scale information for rivers. Conventional, hydroacoustic, global positioning system, and lidar survey methods are applied to developing present-day hydraulics and morphology datasets for monitoring geomorphic, and compiling models. Single and multi-dimensional models are used to inventory habitats under historical, present-day, and future conditions.
The research direction is fundamentally motivated by, and focussed on, biological relevance of physical habitat. Linkages to biotic responses are established through coordination and collaboration with colleagues studying fish, invertebrate, and avian use of riverine habitats. Collaborations to forge biolgical linkages include the Missouri River system, upper Mississippi basin, Southeastern Regional Assessment, the Central Flyway, and the Columbia River.
The strategy for accomplishing this research is to leverage reimbursable funds from partner agencies with USGS program funds. The U.S. Army Corps of Engineers, U.S. Fish and Wildlife Service, and the National Park Service have been contributing partners to all aspects of this research.
