EM 1110-2-1100 (Part III)
30 Apr 02
Figure III-2-4.
Field data relating IR and PR
(e) The K coefficient defined here is based on utilizing the rms breaking wave height Hb rms. The Shore
Protection Manual (1984) presented a dimensionless coefficient KSPM sig = (0.39) based on computations
utilizing the significant wave height. The value of this SPM coefficient corresponding to the rms wave
height Hb rms is KSPM rms = 0.92, which is indicated in Figure III-2-4 with a dashed line for reference.
Judgement is required in applying Equation 2-7. Although the data follow a definite trend, the scatter is
obvious, even on the log-log plot. The dash-double-dot lines represent a 50 percent interval around the SPM
reference line (KSPM rms = 0.92).
(f) An early design value of the K coefficient was introduced for use with rms breaking wave height by
Komar and Inman (1970); KK&I rms = 0.77. This value is commonly seen in many longshore transport rate
(g) Values of the other parameters for use in the sediment transport equations are: ρs = 2,650 kg/m3
(5.14 slugs/ft3) for quartz-density sand; ρ = 1,025 kg/m3 (1.99 slug/ft3) for 33 parts per thousand (ppt) salt
water; and ρ = 1,000 kg/m3 (1.94 slug/ft3) for fresh water; g = 9.81 m/sec2 (32.2 ft/sec2); and n = 0.4. The
breaker index (κ) is .0.78 for flat beaches and increases to more than 1.0 depending on beach slope (Weggel
1972).
III-2-12
Longshore Sediment Transport
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