552 



properly — the quantity of water, the areas of marsh and associated 

 lands, and the types of modifications which have been made constitute 

 the total resource which is presently available. Most of this informa- 

 tion exists, either in available literature or in widely scattered files. 



The data required include "Fills," a tiny word, yet it represents only 

 final and irretrievable damage that can be inflicted on a body of water. 

 Information on circulation-modifying structures of other types — 

 dredged channels, bridges, causeways, small upstream impoundments, 

 et cetera — are also needed. 



It is imperative that records be kept of such construction and that 

 their effects on a system be carefully monitored. These records and 

 monitoring data must be studied minutely in order to learn the most 

 effective and least damging methods to use when estuarine modification 

 is necessary. 



Considered separately these small structures — dikes, weirs, locks, 

 et cetera — appear innocuous, yet even one on a stream tributary to an 

 estuary can have profound effects on salinity levels and current pat- 

 terns. Changes in these, in turn, can upset the ecological balance of an 

 area far out of proportion to the size of the regulation structure itself. 



Though these small flow-regulation structures, along with their 

 larger counterparts, the high dams and large impoundments, may be 

 above tide water, their influence is as important as that of structures 

 within the estuarine zone itself. 



SOCIOECONOMIC DATA 



These data describe the basic economic makeup of an estuarine- 

 associated land area which is usuallv a county, since the county is the 

 smallest unit for which data are available. The majority of data which 

 have been assembled, including those for standard metropolitan statis- 

 tical areas (SMSA's) are relatively gross. They provide an adequate 

 picture at the State or regional level, but are generally lacking in the 

 fine grain detail which would be necessary to do an indepth analysis 

 of a small area. 



Some detail records have been acquired recently and the first step 

 toward a nationwide economic breakdown of small specific areas on 

 the coastline should commence with careful study of the material which 

 is available inhouse. A study of this type would serve two purposes : 

 (1) Full usefulness would be made of the data records already ac- 

 quired, and (2) additional information needs would be clearly pin- 

 pointed. 



The continuing need in this segment of information is not so much 

 one of locating and acquiring additional data. Emphasis should be 

 placed, instead, on constant updating and retention of historical rec- 

 ords for trend establishment, and careful, detailed analyses to present 

 clear and accurate pictures of any area, large or small. 



Section 3. Program Definition 



Table VI.2.1 summarizes the important information lacks found 

 during the initial compilation of the National Estuarine Inventory, 

 and outlines briefly the means by which to acquire each kind of 

 information. 



