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BEsT MANAGEMENT PRACTICEs HANDbooK - Tahoe BMP

BEsT MANAGEMENT PRACTICEs HANDbooK - Tahoe BMP

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8.16.1.2 WAVE RUN-UP FORMULA FOR BACKSHORE DELINEATION (USING THE 80MILE PER HOUR SUSTAINED DESIGN STORM WIND EVENT)The magnitude of wave run-up is influenced by water level, wave height, andbeach morphology and nearshore topography. On wide, gently sloping,dissipative beaches wave run-up is usually low because much of the incomingwave energy is expended in breaking before it reaches the shoreline. Onnarrow, steeply sloping, reflective beaches wave run-up is high becauseincoming waves break right at the shoreline with little prior loss of energy.The wave run-up on the beach is required both for regulatory (backshoredelineation) and engineering purposes. The calculations defined in this sectionshall be used for backshore delineation. The subsequent section gives analternative approach that may be used for engineering processes.The run-up elevation for backshore delineation is based on the followingparameters:• Peak wave period (Tp)• Deep water significant wave height (Hm0)• Beach slope (rs) is calculated using measured beach profile bathymetry and isbased on elevations between the legal minimum and maximum still watersurface elevations (i.e., 6,223.0 to 6,229.1 feet).The procedure is as follows:• Calculate the deep-water wavelength L0:L0g22T p(Equation 16.5)• Calculate the 2% of wave run-up level, represented as R2%:Ru2% 0.27 rsHm0L0(Equation 16.6)• The total wave run-up elevation for backshore delineation is given by:R u 2% SWLmax(Equation 16.7)• SWLmax is the legal maximum still water surface elevation of 6,229.1 feet.8.16.1.3 WAVE RUN-UP (FOR DESIGN)Alternative wave run-up calculations may be used for design, provided thatsupportive information is provided by the project proponent. The followinggives one calculation method, suitable for relatively steep slopes such asrevetments from the Coastal Engineering Manual.TRPA <strong>BMP</strong> HandbookCHAPTER 8: Shorezone Protective Structures and <strong>BMP</strong>s2012 Page 8-103

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