C. Analysis 



The following parameters have proved useful in describing drainage pat- 

 terns in salt marshes: drainage density, mean length of overland flow, and 

 directional orientation of the drainage pattern. 



Drainage density, D^j, is defined as the total length of streams divided 

 by the area of the drainage (Horton 1945). The mean length of overland flow, 



I 



- — r~ . is the mean maximum distance water must flow to reach a 



creek (Horton 1945). 



In order to evaluate the first parameter, drainage density, the total 

 length of creek in a given area must be obtained. Because of the complexity 

 of marsh drainages an indirect method of analysis is needed. The method de- 

 vised assumes that (1) the creeks may be divided into an infinite number of 

 straight segments and (Z) the directions of these segments are randomly dis- 

 tributed. A transparent overlay on which are drawn a series of equally spaced 

 parallel lines is placed over an aerial photograph of the area to be analyzed. 

 The total length of creeks in the area being analyzed is then given by 



L = 1.57 N X a 



where N - number of intersections of creeks and 

 parallel lines on grid 



a - spacing of grid. 



Table 1, 



Analyses of salt marshes adjacent to the Duplin River, 



Sapelo Island. 



Percent "edge" 

 marsh 



a/a 



z. 



61 

 75 

 72 

 67 

 70 

 16 

 13 

 17 

 12 



24 



