Methodology for Predicting Channel Migration (2004) / Chapter Skim
Currently Skimming:
Pages 150-157
The Chapter Skim interface presents what we've algorithmically identified as the most significant single chunk of text within every page in the chapter.
Select key terms on the right to highlight them within pages of the chapter.
From page 150... ...
137 CHAPTER 4 CONCLUSIONS AND SUGGESTED RESEARCH CONCLUSIONS The Problem Approximately 84 percent of the 575,000 bridges in the National Bridge Inventory (NBI) are built over streams.
|
From page 151... ...
138 The Methodology Literature Review The propensity for flowing fluids to meander indicates that this behavior is inherent to shear flows and cannot be attributed solely to local non-uniformity of sediment transport or bank erosion, although both are necessary for meandering in alluvial rivers. While there is still much to be explained about the fundamental causes and mechanisms of meandering, it is clear from the literature that meandering is a natural attribute of most alluvial streams.
|
From page 152... ...
139 different morphology, which requires that each meander must be described quantitatively, and predictions made for a single meander may not be transferred directly to another meander. The conclusion to be drawn from the literature review is that the only complete model of a river is the river itself.
|
From page 153... ...
140 It was also concluded that much of the discrepancy between the predicted and observed distributions of erosion can be accounted for by the fact that meander migration is modeled as a smooth, continuous process. In reality, erosion occurs predominantly in discrete events, and varies greatly both temporally and spatially along the channel from bend to bend.
|
From page 154... ...
141 sinuosity equal-width streams were the most stable, whereas other equal-width streams of lower sinuosity were less stable, and wide bend streams had the highest erosion rates. As presented in the Handbook, this simple stratification of meanders will be of value to the bridge engineer as a screening procedure, allowing preliminary identification of meanders that are very stable.
|
From page 155... ...
142 is present, especially in areas where the bankline is not completely visible or on images with poor resolution. Geologic features, such as clay plugs or rock outcrops, in the floodplain can also limit the usefulness of the overlays because they can have a significant influence on migration patterns.
|
From page 156... ...
143 The Archive Data Base Another deliverable for this project is an archive of the data base compiled on CD-ROM to include all meander site data acquired for this study. The CD-ROM archives contain the Excel workbooks, MicroStation files, 1990s and historic (where applicable)
|
From page 157... ...
144 geographic distribution could permit segmenting the data by geographic or geomorphic region rather than by meander class, leading to regional regression equations for meander migration. However, this approach was considered carefully at the outset of this project, and rejected on the grounds of practicability and budget.
|
Key Terms
This material may be derived from roughly machine-read images, and so is provided only to facilitate research.
More
information on Chapter Skim is available.