Conceptual Model for Predicting Changes in River Pattern and Form, in Response to Management Actions
Lane (1957) and Leopold and Wolman (1957) introduced the concept of channel pattern continuum. Briefly stated, all channel patterns intergrade, and river pattern and form reflects combinations of finite variables. Since the original papers, new studies focused on individual variables and new river pattern classifications have advanced understanding of continuum elements. A conceptual model consolidating key findings under a revised channel continuum could aid Reclamation in predicting the river form resulting from managed water delivery actions.
Questions to be explored include:
* What revisions to the original continuum of channel pattern concept are needed based on significant advances in literature from the past 50 years?
* Can an energy plot of a revised continuum concept represent the affect on river pattern of all main variables?
* How accurate and applicable is this qualitative river model for prediction of river form response to changed conditions?
Need and Benefit
It is difficult to describe river form change in response to one or more changed conditions, yet it is often necessary for Reclamation to make these predictions for its vast array of water delivery projects. On larger projects, numerical models are often used to aid predictions, but in early stages of planning or for smaller studies these models may not be available. Even large projects with numerics require explanation of changes and validation that the model accurately represents field conditions and processes.
Conceptual models can be used for rapid prototyping and timely estimates that aid development of reasonable and defendable management decisions. Classification schemes can sometimes be useful, but some of the natural processes and significant variables are often neglected in development of the schemes. There is a wealth of literature, but no tool that consolidates results from recent investigations for a unified, current, and theoretically-founded model of river pattern continuum and the response of rivers to factors of change.
Qualitative predictions can range widely in the absence of numerical model results. Predictions will depend on the engineers' familiarity with geomorphic processes and their ability to identify important elements of the system. A conceptual model, summarized in figures would help relate a large volume of fragmented geomorphic information into a concise and palatable format. Figures describing river form response to changes in variables could serve as a reference for discussions, preliminary analysis, and project planning and management decisions.
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