when the fetch is sufficiently long. From Figure 1, the relationship 



gj^= 0.146 



(3) 



Where the bottom- friction factor ff = 0.01, and for a given water depth 

 and windspeed, when the initial wave height, H^, at the beginning of 

 the fetch is less than Hg^, the wave will continue to grow in height as 

 it travels across the fetch, with the height approaching the maximum sig- 

 nificant wave height, Hg^;,. When H^ is greater than Hs^^,, it is as- 

 sumed that the wave height will decay as the wave travels across the 

 fetch, with the wave height again approaching the maximum significant 

 wave height, Hg^. 



Where the bottom- friction factor f f > 0.01, i.e., vegetation in- 

 creases the frictional resistance, and the initial wave hei^t H^ < Hg^, 

 it is assumed that the wave will grow to a final height less than or 

 equal to Hg^, but that the growth will occur at a slower rate than 

 where f ^ = 0.01 (Fig. 13). Althou^ the higher frictional resistance 

 may limit the wave growth in this case to a height less than Hg^, no 

 data are available on this effect. Therefore, as a conservative estimate, 

 it is assumed that the maximum significant wave height will have the same 

 value, Hg^, as where ^f - 0.01. 



Where the bottom- friction factor f f > 0.01, and the initial wave 

 height H^ > Hg^, it is assumed that the wave will decay to a final 

 hei^t less than or equal to Hg^, but that the decay will occur at a 

 greater rate than where ff= 0.01 (Fig. 14). Although the higher fric- 

 tional resistance may cause the wave to decay to a height less than Hg^j 

 no data are presently available. Therefore, the maximum significant wave 

 height is assumed equal to the value of Ug^ where fy> = 0.01 as before. 



Where the bottom- friction factor ff> 0.01, the fetch length is ad- 

 justed to an equivalent fetch, F^, which has a bottom friction fj? = 

 0.01, and which will give the same growth or decay as the actual fetch 

 with the actual bottom friction. The relationship between the adjusted 

 fetch, F^, and the actual fetch distance. Ax, is shown in Figures 13 

 and 14. After the adjusted fetch, F^^, has been determined. Figures 1 to 

 12 are used to predict wave growth or decay (see Sees. IV and V). 



1. Determination of Friction Factor . 



Limited data are available to define friction factors for water wave 

 motion through dense stands of marsh grass, brush, or trees. Saville 

 (1952) presented marsh correction factors for correcting values of wave 

 setup over flooded marsh areas. However, this was not extended to pro- 

 vide corrections for wave heights. Whitaker, et al. (1975) developed 

 numerical simulations of water level changes which considered the effects 



23 



