3. If remedial measures are not taken following fixation of 
the inlet, erosion downdrift thereof will be serious with a loss of about 
500,000 cubic yards per year. 
4, In order to correct the conditions created by fixation of the 
inlet, all facets of the problem must be considered and a properly designed 
system selected to cover all foreseeable events. In other words, a struc- 
ture system must be selected to combat the adverse forces created by the 
proposed improvement. 
An important phase of present day design is that the natural flow of 
littoral material across an inlet should be restored after construction of 
jetties. A long updrift jetty preserves the channel to the limit of its 
impounding capacity; when it is filled the material will move around its 
end, A second disadvantage of this type of structure is that the material 
in the impounded area is exposed to wave action and thus difficult to trans- 
port downdrift by mechanical means. In view of these factors, it appears 
that the most satisfactory method of inlet fixation consists of two short 
jetties and an offshore breakwater. With this arrangement jetty length is 
not a major problem since the impounded area forms a short distance updrift 
from the structure. A further advantage lies in the shelter afforded by 
the breakwater, which facilitates sand bypassing by hydraulic pipeline 
dredge. 
The resulting land form includes impounded material updrift from the 
jetties in the lee of the breakwater which is adjacent to the improved 
harbor area. It thus appears that some form of sand fixation in the dry 
area will be required since the prevailing winds and the direction of 
natural forces will undoubtedly carry Some sand from the impounded area 
into the harbor. Fixation by vegetation and plantings is not entirely 
satisfactory since the impounded area will be removed periodically by 
dredging. In view of the above, it is considered that sand fences will be 
more satisfactory for the purpose, 
On the downdrift side of the jetties it is estimated that a loss rate 
of 500,000 cubic yards per year will occur. Since bypassing will be accom- 
plished every other year, with consequent removal of 1,000,000 cubic yards 
in that interval, some provision may be desirable to protect the downdrift 
shores during this period. 
Downdrift the land form is a low narrow sand spit separating the ocean 
from the harbor area. Since the loss rate from this area will be about 
500,000 cubic yards per year, groins will be required to reduce this rate 
of loss if found to be more economical than advance nourishment or periodic 
bypassing. Further, since the spit is low and could be breached during 
storm tide periods, the need for a second line of defense is apparent if 
groins are employed. A bulkhead or revetment, whichever has the least cost, 
may be used, The extent of the groin system is determined by the worth of 
36 
