86 



height to the 2.5 power (Dean, 1976). For the same example of section 5 

 reiterated above, this means that 



Qs ^-^^--) (0^2.5 ^^2) 



Qs (before)- ^^3^)2.5 = ^"^^ 



or a 50% increase in the rate of losses from a beach fill. 



Using two different methods, the approximate cost of maintaining the 

 existing shoreline of Florida with beach nourishment was examined in the 

 NRC report "Responding to Changes in Sea Level: Engineering Implications" 

 (National Research Council, 1987). For the three different scenarios of 

 sea level rise examined, the annual costs range from $33 to $204 per linear 

 meter of shoreline, or between 0.1 and 3.4% of the present day value of 

 beachfront property in Florida. The amount varied by a factor of 2.5 

 between the two methods - highlighting the need for research in this area. 



6.5 RESEARCH NEEDS 



Research needs in the area of modifying shoreline response to sea 

 level rise and the effects of sea level rise on the design of protective 

 works lie in the realm of ongoing basic studies of natural shoreline 

 processes, and have little requirement for specific treatment of sea level 

 rise. If engineers had a surf zone sediment transport model capable of 

 reproducing and predicting beach response to storms and structures, 

 including the effects of sea level rise would mean an almost trivial matter 

 of increasing the mean water depth in the model. However, until the 

 knowledge of basic processes has grown considerably and such models are 

 developed, there is little reason to expect accurate prediction of the 

 response of beaches to sea level rise to be possible, and that cost- 

 effective techniques for modifying the response will be available. 



There are four major areas requiring research in basic physical 

 processes: 1) wave refraction/diffraction, 2) wave breaking, 3) undertow 

 and longshore currents (nearshore circulation) and 4) sediment entrainment 

 under shoaling and breaking waves. The knowledge gained from research in 

 these areas would then be used as input to beach profile and planform 

 response models. 



