Swale - A low-lying or depressed and often wet stretch of land. 



Synergistic - Having the capacity to act such that the total effect is greater 

 than the sum of the effects taken independently. 



Vibroesis survey - A seismic technique using large "loudspeakers" with diaphrams 

 pressed against the ground to produce the wave train (15 to 50 Hz) 

 necessary for seismic measurement. The "loudspeakers" may be mounted 

 on trucks or marsh buggies or carried by helicopter. The frequency 

 range for most efficient seismic operation can be easily controlled 

 by this system. 



Xeric marsh - The higher, somewhat drier portions of a marsh which receive 

 only infrequent water influxes. 



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