Column 15, t' = 2.13 >/38.2' = 13.2 seconds. 



Column 16, — = 1.58 

 d- 



2 



Column 17, K^^ = 0.919. 



Column 18, H = 0.919 (38.2) = 35.1 feet, which is the shallow-water height 



for depth d^ = 110 feet, corresponding to MLW of 104 feet. 



4,970 , , , r 1- , , 



Column 19, N = ^ — = 377 or the total number or waves applicable to 



o 



steady-state significant wave of H = 35.1 feet, say 35 feet . 



Column 20, H_^ = 35.1(0.707) Vlog 377' = 60.4 feet, say 60 feet 



The moving fetch model of Wilson (1955) has been adapted for computer 

 usage by Wilson (1961) . The basic equations were modified by Wilson (1966) . 

 The Bretschneider (1959) model for hurricane wave prediction was modified 

 by Bretschneider (1972) . Borgman (1972) used the results of Wilson (1957) 

 to develop an approach for estimating the maximum wave in a storm which 

 may be considered as an alternate to that presented here. 



3.8 WATER LEVEL FLUCTUATIONS 



The focus now changes from wave prediction to water level fluctuations 

 in oceans and other bodies of water which have periods substantially longer 

 than those associated with surface waves. Several known physical processes 

 combine to cause these longer-term variations of the water level. 



The expression water level is used to indicate the mean elevation of 

 the water when averaged over a period of time long enough (about 1 minute) 

 to eliminate high frequency oscillations caused by surface gravity waves. 

 In the discussion of gravity waves the water level was also referred to as 

 the Stillwater level (SWL) to indicate the elevation of the water if all 

 gravity waves were at rest. In the field, water levels are determined by 

 measuring water surface elevations in a stilling well. Inflow and outflow 

 of the well is restricted so that the rapid responses produced by gravity 

 waves are filtered out, thus reflecting only the mean water elevation. 



Water level fluctuations -- classified by the characteristics and 

 type of motion which take place — may be identified as: 



(a) astronomical tides 



(b) tsunamis 



(c) seiches 



(d) wave setup 



(e) storm surges 



(f) climatological variations 



(g) secular variations 



3-69 



