Minimizing Roadway Embankment Damage from Flooding (2016) / Chapter Skim
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Pages 29-40
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From page 29... ...
27 CHAPTER FOUR HYDROLOGIC AND HYDRAULIC FACTORS INTRODUCTION Hydrologic and hydraulic factors are extremely important in the design of embankments subjected to flooding. These factors control the volume of water that is likely to flood the embankment's surroundings, the duration of the flood, and the water surface elevation.
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28 FIGURE 50 Flood frequency curve obtained from a measured flow discharge hydrograph (Briaud 2013)
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29 tion of the hydraulic radius, the following relationship for a rectangular channel cross section appears reasonable (Briaud et al.
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30 Coastal Parameters The parameters to be considered in a coastal embankment subject to hydrodynamic forces depend on the nature of the flow. Two failure modes that cause surficial erosion were identified in chapter two: overtopping failure mode with three flow mechanisms ("Overtopping" in chapter two)
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31 Regressions equations give the peak flow QT in a river for a given return period T The equations are based on databases of peak flow obtained from gaged stations.
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32 • Soil type information: NRCS Web Soil Survey Web Application (http://websoilsurvey.nrcs.usda.gov/) • Precipitation information: National Weather Service (http://hdsc.nws.noaa.gov/hdsc/pfds/)
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33 Additional information sources include the following: • Jones et al.
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34 • For the submerged flow case (high tailwater) , the difference in elevation between the upstream water level and the tailwater level is not large, the embankment is submerged, and the modified equation is (4.14)
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35 Coastal Surge Overtopping Coefficient Based on Hughes (2008) , it appears appropriate to plug a discharge coefficient value Cf of 0.5443 into the following equation: (4.16)
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36 CASE II: WAVE OVERTOPPING Advances on the determination of overtopping flow parameters have been made based on small-scale and large-scale experiments on levees carried out in Europe (Schüttrumpf et al. 2002; van Gent 2002; Schüttrumpf and Oumeraci 2005)
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37 Where: – hA2% is the peak flow depth exceeded by 2% of the waves, – Hs is the significant wave height [= Hmo] , – CAh2% is an empirical depth coefficient (Table 10)
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38 No published values of Fanning's coefficient exist for armored alternatives. A fist attempt to approximate the Fanning factor was presented by Henderson (1966)
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