and channel levee, overbank complexes that were probable deposited during 

 lowstands and to some extent during highstands of sea- level. (Author). 



172 KOMAR, P. D. 1986. "The 1982-83 El Nino and Erosion on the Coast of 

 Oregon," Shore and Beach . Vol 54, No. 2, pp 3-12. 



The 1982-83 El Nino produced considerable erosion along the coast of 

 Oregon as well as in southern California. The main contributing factors were 

 exceptionally high sea- levels, storms which generated unusually- intense wave 

 conditions, and the northward transport of sand along Oregon beaches. This 

 northward movement of sand was caused by the southward displacement of the 

 storm paths during the El Nino, and is unusual for the Oregon beaches where 

 near-zero net littoral sand transports normally prevail. This northward sand 

 movement was particularly important in governing the locations of beach ero- 

 sion, being greatest to the north sides of headlands while sand accumulated to 

 their south sides (the headlands acting much like groins). Particularly se- 

 vere erosion has occurred on Alsea Spit where the northward sand transport de- 

 flected the inlet, erosion that still continues in direct consequence of the 

 1982-83 El Nino even though three years have passed. 



It is unclear as to the extent of the role played by previous El Ninos 

 in Oregon-coast erosion. The 1972-73 and 1975 erosion episodes on Siletz Spit 

 occurred during El Ninos, and the high storm-wave energies important to that 

 erosion were likely associated with the El Ninos. On the other hand, there 

 was no accompanying northward sand transport, rip -current embayments instead 

 playing a major role in focusing the erosion. From this it appears that El 

 Ninos can be a factor in causing Oregon coast erosion, principally by the 

 higher wave energies and perhaps increased sea- levels that accompany this phe- 

 nomenon. But it is also clear that the 1982-83 El Nino was a highly excep- 

 tional event, and the erosion response to more typical El Ninos will not be 

 nearly so great as experienced during this past occurrence. (Conclusions). 



173 KOMAR, P. D., and ENFIELD, D. B. 1987. "Short-Term Sea-Level Changes 

 and Coastal Erosion," Nummedal, D., Pilkey, O.H., and Howard, J.D., eds . , Sea- 

 Level Fluctuations and Coastal Evolution . Special Publication No. 41, Society 

 of Economic Paleontologists and Mineralogists, Tulsa, OK, pp 17-28. 



Investigations of the role of sea-level in producing coastal erosion 

 have focused mainly on the long-term rise due to melting of glaciers and 

 thermal expansion of sea water. There are, however, additional shorter term 

 changes in the local sea-level produced by a variety of ocean processes. 

 Variations in the coastal currents, for example, can alter the water level at 

 the shoreline due to the geostrophic balance between the current and the 

 offshore sea-surface slope. Other factors which may alter local sea-level 

 include changes in atmospheric pressure, winds blowing either in the longshore 

 or cross-shore directions, and the occurrence of upwelling. Because the 

 inclined continental shelf and slope act as a wave guide, the fluctuations 

 often become trapped and propagate over longshore distances beyond where they 

 are actually generated. In that many of these processes are typically 

 seasonal, the responding sea- level also has a pronounced seasonal cycle, but 



81 



