523 



Each of these major sections contain many individual parameters 

 which were selected to att- mpt a full description of pertinent 

 characteristics. 



SELECTION OF DESCRIPTORS 



Four criteria governed the selection of descriptors : 

 Availability 



Although selected primarily on the basis of importance to manage- 

 ment, where possible parameters reported on a national basis by a 

 Federal agency were selected. Elsewhere, data in standard professional 

 usage in the respective fields were used. Provision has been made to 

 include additional types of data as the state-of-the-art advances. 



Meaning 



Each descriptor is a valid measure of some system characteristic 

 needed for either technical or institutional estuarine management 

 purposes, 



GomfpatihUity 



Each descriptor is either directly informative or can be compared or 

 combined with other descriptors to be meaningful. For example, except 

 in extreme cases, tide range along is not a useful management statistic ; 

 but in combination with the area of the estuarj^, it can help in deter- 

 mining flushing characteristics and overall ability of the system to 

 rid itself of pollutants. 



Uniqueness 



Each descriptor is a fundamental datum; that is, it cannot be 

 derived from other information included in the inventory. 



For two reasons, 1950 has been set as an arbitrary cutoff date for 

 most historical data. First, water quality and waste discharge infor- 

 mation, and many kinds of economic data extremely pertinent to the 

 needs of this study, were rarely collected before that date. Second, 

 ecological and biological changes caused by estuarine alteration before 

 that date would scarcely be discernible now, nor could their causes 

 be traced. 



Section 2. Estuarine Register Areas 



As another means of organizing the pertinent information, a classifi- 

 cation scheme for the estuarine areas of the United States was 

 developed. 



The entire coastline was divided into subdivisions called estuarine 

 register areas (ERA). (Seefig. VI.1.2) 



