To achieve reasonably accurate results in using the method, engineering 

 judgment is required to assure the following conditions will exist at and near 

 the harbor : 



(a) Sediment will enter the basin in suspension; bedload transport 

 will be negligible. 



(b) Water will enter or will be discharged from the basin through 

 the channel as the water surface rises or falls in nearby navigable 

 waters. 



(c) At any given time the flow in the channel will be unidirec- 

 tional or nonexistent; i.e., the volume of water that will enter the 

 basin as the water surface rises will be equal to the volume of the 

 basin above the sill. If no sill exists, z = basin bottom eleva- 

 tion; if the sill elevation or basin bottom elevation is below MLLW, 

 z g = MLLW = 0. 



(d) Water in the basin will be trapped below sill elevation. When 

 a sediment particle settles below that elevation, even though it has 

 not yet reached bottom, the particle is considered deposited. If no 

 sill exists, bottom scour is assumed to be nonexistent. 



(e) Shoaling rates and the sedimentation processes will be uniform 

 throughout the basin; no back, eddies or other areas of preferred sedi- 

 mentation will exist within the basin. 



III. PROCEDURE 



A mathematical model has been developed in integral form to predict 



sedimentation rates in enclosed harbors (Everts, 1977b). For many general 



situations the model has been solved numerically, and the results are pre- 

 sented in this report. 



1. Data Requirements. 



Information required to use the model includes (a) tidal or river hydro- 

 graphs at the harbor site, (b) concentration of suspended sediment that will 

 be carried into the harbor, (c) settling characteristics -of the suspended 

 sediment, and (d) proposed harbor geometry. 



a. Tidal or River Hydrograph. The volume of inflow water to the basin is 

 obtained using the tidal or river hydrograph. In this procedure, a simple 

 cosine function is assumed to approximate the rise and fall of the water sur- 

 face; i.e. , 



a c / 2irt\ 

 n --§■ (l - cos ) (1) 



where 



n = water surface elevation 



a = tidal amplitude or maximum river stage variation 



T = tidal period or duration of a complete rise and fall of a river 

 hydrograph 



t = time past low water 



