River Crossings: Evaluation of Meander Migration As an Integrity Hazard

TGN operates a system of 9,000 kilometers, with a long stretch traveling next to the foothills. Although it is clear now that this path may not be the best choice, it was defined for access convenience parallel to a national highway back in 1960, when erosion was not an important issue. Whenever a pipeline crossing is located at a place where a river experiences a break in its slope, development of meanders poses a significant threat to its integrity. The interaction between a rigid structure and a changing environment sets the scenario of a problem that needs constant attention. Thus, meanders become the main cause that leads to the implementation of expensive remediation works. In the following paragraphs, a method of evaluating meanders is presented based on concepts of channel stability regarding river curvature, width, slope and flows. This is complemented with real cases in which theoretical aspects are matched with actual crossings, its construction characteristics and the evolution of meanders with time. Long term performance of typical solutions such as soil movement channeling, bank protections, jetties and pipeline lowering are compared. Finally the inverse problem is addressed in which guidelines for the design of a new crossing are listed.