a. Step 1 — Sediment Mass Entering Harbor . During a rising tide, or ris- 

 ing river stage, the mass of sediment carried into the harbor is dependent 

 upon the concentration of entering suspended sediment, the characteristics of 

 the tidal or river hydrograph, and the geometry of the proposed harbor. For a 

 harbor basin with vertical sidewalls and ' no sill (z g = 0; Fig. 1), and into 

 which the entering concentration of suspended sediment is constant (c^ = c) 

 (k = 0; eq. 2), the total mass of sediment, M, which enters during a 

 floodtide cycle is 



M = c a„ A 



(3) 



where A is the surface area of the basin. When a sill is considered 

 (z > 0) , but the entering concentration is constant through time (k g = 0) 

 and the sidewalls are vertical, the mass which enters is 



M = c A(a s - z s ) (4) 



With a sill and vertical sidewalls, but when the concentration of inflowing 

 sediment varies with time (k ^ 0) , the mass which enters is 



M = c 



AK 



where K is the sediment-concentration correction coefficient, 

 are given in Figure 2. 



(5) 

 Values of K 



0-1 



Figure 2. Sediment-concentration correction coefficient, K, as a function 

 of a linear, time-dependent change in suspended-sediment concentra- 

 tion, k (see eq. 2) and sill elevation, z g , where z g is some 

 part of the maximum water surface elevation, a g . This figure, 

 used in calculating the sediment mass which will enter a harbor, 

 provides a correction procedure for situations where the entering 

 suspended-sediment concentration varies with time or when the sill 

 elevation is above MLLW. 



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