54 MULTIPLE PURPOSE RIVER DEVELOPMENT 



competitive model. To a certain degree a water-derived commodity 

 or service provided to satisfy the want of one individual will also 

 render simultaneous satisfaction to other individuals, irrespective 

 of how exclusive the intent might have been. The reason for this 

 has been neatly summarized: 



Evidently there are not many common wants whose individual 

 gratification is absolutely impossible, which can be satisfied 

 eo ipso only for a group of individuals and which consequently 

 may be called absolute group wants. . . . Likewise, the great 

 majority of common wants can be gratified, discretely and sepa- 

 rately, for the individual members of the community. ... As a 

 rule, the only essential question is the difficulty or ease — and on 

 the basis of virtually the same consideration, the expensiveness 

 or cheapness — of such an individual satisfaction. ^ 



FLOOD CONTROL 



Perhaps the most common example of collective or group 

 demand for a water derivative appears in the case of flood protec- 

 tion. A system of levees, if undertaken to provide protection to 

 any member of a community, will provide protection to all who 

 inhabit the protected area.^ Or, to extend the example, any system 

 of tributary storage reservoirs required to control runoff and 

 protect one community at some point along the main stem will 

 incidentally and automatically afford some degree of protection 

 to other communities along the same reach of the river.^ Usually, 

 it is prohibitively costly to provide such protection to an individual 

 or a single community, when compared with the value to them 

 alone; but in many cases, the cost becomes economically justified 



^ Theo Suranyi-Unger "Individual and Collective Wants," Journal of Political 

 Economy, February 1948, p. 17. 



^ There always remains the relatively expensive possibility that each occupant 

 of the flood plain will construct protective works around his property, as did 

 Samuel Colt, the manufacturer of the Colt revolver. See W. G. Hoyt and Walter 

 B. Langbein, Floods (Princeton: Princeton University Press, 1955), p. 202. 



^A side issue, representing a qualification of the assumptions of our model, is 

 the case of channel straightening, dredging, and levee construction, which — 

 while facilitating the flow past a given point on a river — may contribute to the 

 flood stage at another. This will represent an external diseconomy resulting 

 from direct interdependence, of which there are many examples in the water 

 field. 



