beach material, movement of this material by waves and currents, and its 
ultimate accumulation as a beach deposit. The balance between erosion and 
deposition, and the natural forces that control dominance of one or the 
other, are also of concern to the geologist, 
In his study of beaches the geologist relies mainly on field observa- 
tions, complicated as they may be by multitudinous events that take place 
simultaneously along the shore. These include the interplay among waves, 
currents, and tides, and the corresponding responses shown by beach deposits 
under these controlling conditions. The geologist evaluates this complex 
situation in terms of relatively long spans of time, viewing the phenomena 
of a given instant as the momentary end product of a succession of events 
that start with the inception of a beach deposit, and end with a mature 
beach that represents some balanced state between erosion and deposition. 
The engineer is concerned with those aspects of shore processes that 
control erosion and deposition at a given time and place. He seeks for 
principles that permit an enlargement of beaches and design of shore pro- 
tective structures appropriate to relatively well-defined needs. The 
engineer thus supplements the largely qualitative field observations of 
the geologist with quantitative study of shore processes in controlled 
wave tank experimentation. These experiments yield much basic data on 
factors that control beach slopes, movement of sand by waves and currents, 
formation of offshore bars, and other specific aspects of shore processes. 
Wave tank experimentation involves scale model theory, and requires 
simplification of natural shore processes to those features that can 
ultimately be expressed as a physico-mathematical model. Extension of 
these experimental findings to their natural scale, combined with field 
measurement of wave forces on coastal structures, furnish data necessary 
for installing protective structures or enlarged beaches which are them- 
selves not destroyed or removed by the very forces that they are designed 
to control, 
In recent decades the geologist has increasingly quantified his field 
observations, and the beach engineer has increasingly taken the framework 
of geologic observation into account in his own work. Moreover, advent of 
the high-speed computer has made readily available a variety of ways in 
which the complexly interlocked variables of beach processes and deposits 
can be analyzed in greater detail than was feasible by hand calculation. 
The way has thus been opened for more fundamental field studies on the one 
hand, and for more comprehensive wave tank experimentation on the other, 
as the variety of models applicable to the study of shore processes and 
deposits is enlarged. 
The purpose of this paper is to examine the geological framework 
of beach processes and deposits in which the beach engineer operates. 
The approach is to set up a conceptual model of the beach deposit as a 
