Obviously, groin design is important here, as is also developed by Hall 
(1963). 
Erosion and deposition along shorelines play an important part in the 
selection and effectiveness of beach engineering structures. This can be 
illustrated by the two diagrams in Figure 8. As mentioned earlier, ag- 
gradation along the foreshore moves the berm seaward, and adds sand to the 
natural “storage bin" represented by the backshore. With adequate back- 
shore width, the bank in the upper cross-section of Figure 8 is effectively 
protected from wave action. Thus, in terms of the model of Figure 5, the 
geometric response of the beach with aggradation is such that a natural 
buffer zone is developed between wave uprush and the bank in the hinterland. 
If shore drift is so lean that waves and currents strip material from 
the foreshore, the landward movement of the berm narrows the protective 
backshore, resulting in the loss of sand from the natural storage bin. In 
the extreme case shown in the lower diagram of Figure 8 erosion has con- 
tinued until the bin is empty, and the foreshore extends directly to the 
bank, In these circumstances the bank is subject to nearly continuous 
wave action, and the final erosional response of beach geometry has been 
that no backshore remains. 
The beach engineer, faced with the problem in the lower diagram of 
Figure 8, has several choices for remedial action. One may be to build 
groins along the shore, perhaps with a fill of imported sand, to establish 
a berm some distance from the bank. If erosion is very severe, and if 
costs of beach restoration are prohibitive, the engineer may recommend a 
seawall to protect the bank, even at the risk of losing the remaining sand. 
Decisions of this sort require not only judgment regarding the kinds of 
structures to use, but involve cost factors as well. Thus, the beach 
engineer, in taking the conceptual beach model into account, superimposes 
upon it a cost factor, and accordingly introduces man-made components 
into the model. By introduction of the economic factor and other re- 
straints, the conceptual model becomes adaptable to various kinds of 
operational research studies. 
CONCLUDING REMARKS 
The treatment of shore processes in this paper is expository in 
terms of a conceptual beach model, and it does not include information 
on rates of erosion, quantities of shore drift, or related items. Much 
data are available on these quantitative aspects, and for applied use of 
the conceptual model such information is used to convert the expository 
treatment into a more formal quantitative treatment for analysis of data 
matrices, aS was mentioned in connection with Figure 7. 
There seems little doubt that improvements in instrumentation and 
better understanding of interrelations between process and response 
elements have made it possible to design field experiments on beaches 
