inlet. Because of the construction, ebb tidal currents will no longer hold 

 part of the ocean bar offshore of the inlet; the ebb currents are directed 

 offshore in a narrow hydraulic jet allowing waves to move a part of the 

 offshore bar shoreward and eventually into the deposition basin. Dredging 

 during the first several years after construction may therefore exceed normal 

 requirements. A part of the offshore bar may remain seaward of the newly 

 constructed jetties but it will be much smaller in size than the precon- 

 struction bar. 



Initial dredging of the deposition basin and navigation channels often 

 requires removal of more sand than is necessary for construction of sand dikes 

 or other project appurtenances. Although the material may not be required 

 initially, it is a valuable resource and should be stockpiled as dunes along 

 the updrift and downdrift fillets for possible future use as beach nourishment 

 along adjacent beaches and as an additional defense against breaches outside 

 the jetties. 



5. Updrift Beach. 



Alinement of the updrift beach is governed by the wave environment and 

 wave reflection, refraction, and diffraction in the vicinity of the jetty 

 structures. Generally, beach width near the updrift jetty is established by 

 the length of the sandtight, shore-connected leg of the jetty. Shoreline 

 location along the updrift beach at any instant depends on the longshore 

 transport history at the site. After extended periods of downcoast transport, 

 the fillet adjacent to the weir will usually be full and the beach wide; after 

 periods of upcoast transport the fillet may be empty (except for the sheltered 

 area immediately in the lee of the jetty) and the beach relatively narrow. 

 The magnitude of fluctuations in shoreline location is determined by wave 

 height, period, and direction variability. The condition of the updrift beach 

 at any time depends on the transport conditions that prevailed before the time 

 of observation. Prediction of beach response requires a knowledge of the 

 longshore transport environment that includes the frequency and duration of 

 reversals as well as the net and gross transport rates. Several methods which 

 are available for predicting beach response to the construction of jetties 

 range from simple extrapolation of the existing updrift beach alinement toward 

 the inlet to the mathematical simulation of beach changes by performing 

 sediment balance calculations for small beach cells. 



6. Downdrift Beach. 



Shoreline alinement, range of shoreline fluctuations, and location of the 

 bypassed sand disposal area are characteristics of the downdrift beach that 

 need to be determined. Like the updrift beach, the alinement of the downdrift 

 beach and the range of onshore-offshore movement of the shoreline depend on 

 the longshore transport environment and transport history at the site, the 

 frequency and magnitude of bypassing operations, and where the bypassed sand 

 is placed along the downdrift beach. If the bypassed sand is placed too close 

 to the downdrift jetty, the sand could move into the lee of the jetty and fail 

 to nourish downdrift beaches. 



Timing of the bypassing operation is also a factor. If bypassing is 

 performed when transport is in the upcoast direction, bypassed sand will be 

 carried toward the inlet and may enter the navigation channel. Bypassing 



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