W.S. Richardson, Techniques Development Laboratory, National Weather 

 Service [personal communication, 1976). This list includes all 

 "storms" defined as having a recorded tide gage surge greater than 

 0.6 meter (Table 4) but only for the months of November through 

 March (i.e., storms occurring in the other months were not tabulated 

 by Pore, Richardson, and Perrotti, 1974). This average of extratropical 

 storms of three per year agrees well with other longer term averages 

 for the Hampton Roads area (Pore, Richardson, and Perrotti, 1974, 

 Fig. 4). Beach observations in this study indicate that the major 

 factor concerning the occurrence of erosion is the height of the 

 storm surge, which allows even moderate-size waves to erode parts 

 of the beach (Warnke, et al., 1966). 



There are, of course, problems in relating storm surges measured 

 at Hampton Roads, within the southwest part of Chesapeake Bay, to 

 storm-induced erosion occurrences on the ocean shoreline which lacks 

 sufficient tide gage records. However, Richardson's data show that 

 at the time of most measured surge occurrences, the peak winds were 

 blowing from the northeast or east. Although the peak winds given in 

 Table 4 are the daily peaks, these data were cross-checked by 

 Richardson against peak winds at 3-hour intervals, to verify the 

 directions as representative of surge conditions. The surge height 

 was the maximum hourly observed value, with most surges lasting at 

 least several hours. (W. S. Richardson, personal communication, 1977). 



These surges are generated by hurricanes (Harris, 1963) and 

 extratropical storms (Pore, 1964). The surges associated with 

 hurricanes are generally higher than those surges associated with 

 extratropical storms. However, the duration of the hurricane surge 

 is generally shorter than the duration of the extratropical surge. 

 The long duration of the extratropical surge almost guarantees 

 that it will last through one high tide, while the shorter lived 

 hurricane surge may completely miss a high tide (e.g.. Hurricane 

 Belle in August 1976) . 



The time of occurrence of the storm surge with respect to the 

 normal high tide is of great importance because it can mean the 

 difference between serious and minor flooding. The Norfolk harbor 

 experienced serious flooding during an August 1933 hurricane when 

 water levels of 8 feet (2.4 meters) above MSL were recorded (U.S. 

 Army Corps of Engineers, 1970). Unfortunately, as previously in- 

 dicated, these data are from inside the bay, which may be quite 

 different from the ocean shoreline study area which lacks a tidal 

 gage. 



45 



