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Of all our land types, the coastal regions are one of the most limited. 
I think a reasonable land use policy with respect to such a limited 
resource, would be to restrict its use to those things which must be 
there because they, by their nature, cannot be located anywhere else. 
A. Lanp Use—Estvarine INTERACTIONS: SOME CONSIDERATIONS 
(By Bradford Butman, MIT) 
INTRODUCTION 
The biologic importance of the estuarine zone has often been ne- 
glected or overlooked when planning land use. This has occurred pri- 
marily for two reasons: first, the ecological value of estuarine land is 
not generally reflected in the market price, and second, it is often 
difficult to predict whether a land use will have a significant effect 
on the estuarine environment. A simple scheme is proposed which 
will identify when a land use could affect estuarine biology. Identifi- 
cation of possible land use—estuarine interaction is a necessary start 
toward intelligent land use planning. To determine the actual magni- 
tude and significance of the interaction in any particular situation 
will require further detailed study. 
BACKGROUND 
Pritchard defines an estuary as follows: 
An estuary is a semienclosed coastal body of water which has a free connection 
with the open ocean and within which sea water is measurably diluted with fresh 
water derived from land drainage.! 
In general, an estuary exists where the land meets the sea and there is 
fresh water inflow. Estuaries are mixing zones where fresh water con- 
taining 1 part per thousand or less of dissolved salts gradually mixes 
with sea water containing 35 parts per thousand dissolved salts. Much 
of the estuary is under tidal influence. Estuaries have also been defined 
as areas where there is significant fresh water influence. These areas 
may extend many miles offshore. This paper will be concerned pri- 
marily with the more conventionally defined estuaries, but it should 
be kept in mind that the influence of land activities on the ocean 
does not stop at the coastline. 
Development in the United States has historically been on the 
coastline and particularly near estuarine areas where both river and 
ocean transportation are easily accessible. The coastal counties of the 
USS. contain 33% of the population, four-fifths of it in urban areas, 
but only account for 15% of the land area.? Forty percent of all 
manufacturing is located in the coastal counties. With such dense 
population and industrialization, estuarine regions have many use 
conflicts. Use of the estuary for cooling water supply, waste disposal, 
urban development, transportation and recreation compete with its 
natural function as a biological habitat. 
Estuaries are ecologically important because they are tremendously 
fertile regions, producing more food than is usable in the estuary itself, 
1D. W. Pritchard, “What is an Estuary: Physical Viewpoint” in Estwaries, ed. by G. H. Lauff, Ameri- 
can Association for the Advancement of Science, publication 83. (Baltimore, Md.: Horn-Schafer Co., 
1967), p. 3. E : 
2 Federal Water Quality Administration, U.S. Department of Interior, National Estuarine Pollution 
Study (Washington, D.C.: U.S. Government Printing Office, 1970), p. 148. 
