DISCUSSION 



Chronic: I am speaking entirely as a novice here, but at the outset it 



seems to me that perhaps drainage patterns in marshes are 

 not quite as typical as other drainage patterns as I was led to 

 believe because they are caused by a different sort of physical 

 circulation in and out. The drainage patterns that we see on 

 land are all caused by drainage down. These may very w^ell 

 have an upward influence which makes them a little bit different 

 in the formation than the common drainage patterns that we see 

 on land. 



Ragotzkie: It is a two-way system, but on the flood tide the water flowing 



up these drayiage patterns is moving at a lower velocity than it 

 is on the ebb because there is less hydraulic gradient behind it. 

 The maximum current velocities are developed on ebb. In other 

 words, ebb dominates the form, although in the headward areas 

 we have flooding across divides, and I do not think it is clear 

 up there whether these are ebb dominated or not. 



Bradley: I would like to go back to your first point where you made your 



theoretical determination of the relation between the ebb and 

 flood tide because a few years ago we measured the tidal veloc- 

 ities at a level of about one -tenth of a foot above the flat on a 

 large tidal flat on the Maine coast. We found consistently that 

 the flood current was between 15 and 20 % higher, reached higher 

 peaks, than the ebb current. This is away from channels. 



Redfield: I think this raises a very interesting question with regard to the 



tidal regime in shallow water areas which bother the tidal 

 theoreticians very much because there are no longer simple ■' 

 sine waves. In a shallow area the tide goes this way: The 

 elevation tends to rise abruptly and there is a much prolonged 

 ebb. Very frequently in such bays as we have along this coast 

 of the shallows it will divide up about five and seven hours and, 

 of course, the velocities then would be higher on the flood and 

 lower on the ebb; so this is quite the reverse of what Dr. Ragot- 

 zkie has seen here. It's quite obvious that we've got to consider 

 the shape of the basin and the elevations of the marshes very 

 much. In other words, we have a rather special tidal problem 

 which certainly would deserve'a great deal of further investi- 

 gation. ■ 



The other point is with regard to the evidence of the pattern re- 

 lated to whether the marsh is sedimenting rapidly or not. One 

 gets the impression that these marshes are sedimenting very 

 much more rapidly than the New England marshes where we do 

 not have any soil to produce sediment. It will be extremely in- 

 teresting to make a quantitative comparison of a New England 



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