Doctoral Dissertation Research: The Development Of A Framework For Quantifying Hydrologic Surface Connectivity Of A Costal River-Floodplain System
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This doctoral dissertation research project will develop a framework for analyzing the degree of connection between a river and its floodplain considering its hydrologic conditions, geomorphic patterns and processes, and the distribution of vegetation within the floodplain. The productive and diverse nature of rivers and their floodplains and the ecosystem services they provide is greatly influenced by and dependent on river-floodplain connectivity. Losses in river-floodplain connectivity due to human impacts across the globe has been well documented, but quantifying these losses has been complicated by a lack of formal framework for quantifying landscape connectivity within floodplains. This project will develop a framework that combines the hydrologic surface connectivity concept with graph/network theory. Such a framework will help advance scientific understanding of river-floodplain processes as it will consistently quantify measures and ultimately permit these systems to be categorized and compared using a standard approach. Moreover, this more standard approach will find a useful application in the development of environmental flow policies for many rivers. As a Doctoral Dissertation Research Improvement award, this award also will provide support to enable a promising student to establish a strong independent research career. Graph theory has been widely used within the fields of hydrology, geomorphology, and ecology to characterize connectivity and its attributes within landscape systems. This makes graph theory well-suited for the development of a framework for characterizing river-floodplain systems using a landscape connectivity perspective. The two objectives of this project are: (1) to quantitatively determine how hydrologic surface connectivity varies within a specific river-floodplain system for the four methods (morphometric analyses, field-based direct measurements, image analyses, and numerical modeling) commonly used to analyze hydrologic surface connectivity; and (2) to evaluate the similarities and differences amongst the family of hydrologic surface connectivity indicators and to determine the effectiveness with which each method captures attributes of the riverine landscape system. The first objective will be addressed by applying graph theoretical measures for quantifying landscape connectivity to estimates of hydrologic surface connectivity determined using field data, imagery analysis, and modelling techniques. These have been used in the past, but not consistently. The second objective will be addressed using results from the first objective in order to compare estimates of connectivity and its attributes for each approach used in determining hydrologic surface connectivity. The similarities and differences amongst the connectivity measures will be used to determine how well each method for analyzing hydrologic surface connectivity captures aspects of river-floodplain process. A case study of the Mission River in Texas will be used to develop this framework and determine its utility.