Equations (3), (4), and (5) are applicable for basins with vertical 

 sidewalls. If the sidewalls are sloping, the average plan area should be 

 calculated for the half-full elevation above the sill. The actual sediment 

 mass input may be slightly larger than that calculated using equation (5) if 

 k > 0, and slightly smaller if k < (the difference is small compared to 

 other uncertainties in using this method). 



b. Step 2 — Sediment Mass Deposited in Harbor . Of the total sediment 

 mass, M, carried into the harbor (eqs. 3, 4, or 5 of step 1), the part 

 deposited is primarily dependent on the settling characteristics of the 

 sediment, the distance the sediment has to settle to be deposited, the time 

 interval during which the suspended material settles, and the elevation of the 

 sill. Figure 3 shows the part of the sediment deposited, P, as a function 

 of tidal range, a g , and particle size, d g . For harbors influenced by tide 

 behavior as compared to floods of longer duration, the settling 

 characteristics of disaggregated particle sizes finer than d g = 0.001 

 millimeter are such that very little material will be deposited in the 

 harbor. For d > 0.03 millimeter nearly all the sediment which enters the 

 harbor will be deposited. The P values shown in Figure 3 are for z = and 

 k = (eq. 2) conditions. Corrections must be made for these parameters when 

 they are not zero. 



1.0 pq 



T=l2.4hr T = 24.8hr 



Particle Size, d s in mm 



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Tidal Amplitude , a s (m) 



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Figure 3. Part of sediment, P, deposited in the harbor basin as a function 

 of tidal range or river rise in the basin, a g , and particle size. 

 Sill elevation is zero. The sediment concentration entering the 

 harbor is nonvarying with time; i.e., k = (see eq. 2). Sediment 

 size is related to settling velocity for quartz spheres in 

 freshwater at 20° Celsius. 



11 



