It can be shown that with reasonable assumptions, the ratio of 

 Incident wave height H^^, seaward of a stand of marsh grass, and 

 height Hjj^g, landward of the stand of marsh grass, are related as 

 follows : 



H 



Jle 



1 + AHj. 



where 



CpDA 



A = r- 



311 S^d 



Cjj = Drag coefficient («1.0) 



D >= grass stalk diameter 



I = length of "stand" through which waves propagate 



S = average spacing of grass stalks (assumed on square 

 centers) 



d » water depth (assumed to be constant) 



Example: Consider the following: grass stalks 4 millimeters In 

 diameter on a 6-centlmeter spacing In a water depth of 25 centimeters 

 extending over a stand length, I, of 10 meters. For this example 

 an Incident wave height, Hj^, of 15 centimeters will be considered. 

 The height, Hj^g, at the landward end of the stand Is 



'D 



A = 



Cn HI 



A = 



3Tr S^d 

 1(0.4)1000 



3Tt(6)225 

 A = 0.0471 



and 



H 



le I + AR^ 

 15 



le 1 + 0.0471(15) 



H - 8.8 cm 



ie 



14 



