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<br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br /> <br />AYRES <br /> <br />excessive flow (in the model) even if the water cannot physically get to that area. (3) <br />One-dimensional assumptions are particularly problematic at skewed highway <br />crossings with multiple openings and overtopping such as U.S. 36 and Highway 93. <br />Ayres Associates' experience in applying 2-dimensional models at highway crossings <br />has shown us that along the area of the road embankment that is farther downvalley. <br />higher water surfaces and flows are likely to occur than a 1-dimensional model would <br />predict. In order to apply a 1-dimensional model to this situation, the model would <br />have to include liberal use of ineHective flow areas, blocked obstructions and split flow <br />simulation. A 1-dimensional model of this complexity would be difficult to make <br />comprehensible to the general public. (4) Therefore, because of this complexity, the 1- <br />dimensional results will be nearly impossible tor the public to understand, jeopardizing <br />a major project goal. <br /> <br />Benefits of 2-dimensional Modeling <br /> <br />Although the term w2-dimensional modeling" is meaningless to the general public, the <br />results of 2-dimensional modeling can be demonstrated graphically through a variety of <br />flow visualization techniques. Therefore, the results can have great meaning when <br />presented appropriately. Two-dimensional modeling also avoids the technical <br />limitations of 1-dimensional modeling described above. Flow will only get to areas if <br />the water can physically traverse the intervening area. Two-dimensional models can <br />accurately depict whether water will pond along the downvalley area at a skewed <br />highway embankment. This is illustrated in Figure A, where water surtace rise is <br />shown along a highway crossing. This figure shows how at a skewed crossing (such <br />as U.S. 36), water will pond in the downstream skewed area and would cause greater <br />overtopping and flooding potential. This is a condition that 2-dimensional modeling is <br />best suited for simulating. These types of plots will be developed for the South Boulder <br />Creek with map and aerial photo backgrounds to emphasize flow path locations. <br /> <br /> <br />,~ <br /> <br />,~ <br /> <br />'" <br /> <br />.00 <br /> <br />.00 <br /> <br />.00 <br /> <br />.~ <br /> <br />'" <br /> <br />.00 <br /> <br /> <br />Figure A. Water surtace rise along skewed highway embankment (flow is from top to <br />bottom). <br /> <br />20 <br />