Synthesis of Hydrologic and Geomorphic Drivers of Riverine Habitat Dynamics Active

The Issue:

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.

Natural and human-influenced disturbances are transmitted through watersheds and may diminish or grow as they 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.

Addressing the Issue:

CERC scientists are developing a predictive understanding of rates and processes of river corridor habitat dynamics resulting from hydrologic and geomorphic sources by:

• Using Historical, stratigraphic, dendrochronologic, and photogrammetric methods long-term habitat datasets
• Compiling water-shed scale information for rivers using geographic information systems
• Developing present-day hydraulics and morphology datasets for monitoring geomorphic, and compiling models using conventional, hydroacoustic, global positioning system, and lidar survey methods  
• Compiling inventory habitats under historical, present-day, and future conditions using single and multi-dimensional models

Next Steps:

• 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
• Provide fundamental research into physical and chemical processes affecting river-corridor habitat structure and function, and their resilience under changing environmental conditions
• Address how re-engineering of large river channels interacts with restoration of flow regimes to provide ecosystem services for threatened and endangered species
• Re-engineering of river corridors for habitat promises to decrease flood hazards by providing increased floodplain storage and by removing infrastructure from the floodplain
• Describe functional relationships among aquatic species and habitats to provide information to conserve or restore aquatic community structure and function

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Return to River-Corridor Habitat Dynamics Research

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