53 



The l)RAiNA(iK Area of the East Fork of White River. 



Ciiari.es W. Shannon. 



"Every river appears to consist of a luaiu trunk, fed from a variety 

 of branches, each running in a valley proportioned to its size, and all of 

 them together forming a system of valleys, communicating with one an- 

 other, and having such a nice adjustment to their declivities that none of 

 them join the principal valley either at too liigh or too low a level, a cir- 

 cumstance which would be infinitely improbable if each of these valleys 

 were not the work of the streams flowing through them."* 



Streams are among the most important agencies which give form and 

 expression to the surface of the land. The study of streams, therefore, 

 involves to a great extent the consideration of the nature and origin of 

 many topographic forms — hills and mountains, plains and valleys— and 

 the changes they pass through. 



Every person is familiar with the manner in which the rainwater 

 that falls is gathered into rills, rivulets and l)rooks, which unite to form 

 larger rivers. Every one is aware, also, that streams are turbid after 

 heavy rain. Yet comparatively few people have thought of the woi'k and 

 change upon the surface of the land which is done by even the smallest of 

 the rills and all along the course of the river ; nor have they thought that 

 the smallest rill down the hill slope or along the I'oadside is adding to the 

 work of the large streams, or adding to the extent of the drainage area of 

 the stream. 



The drainage area of a stream is the land area which is drained by 

 the main stream and all its tributaries — and the tributaries of the tribu- 

 taries. 



The drainage area of the East Fork of White River is composed of the 

 western central and southern part of Indiana, including the greater part 

 of twenty-five of the ninety-two counties of the State, and a total of about 

 7,000 square miles, or a little less than one-fifth of the total area of In- 

 diana. This area is mapped out in full on the accompanying map, with 

 the exception of a few counties lying to the north of the area shown. 



•Illustratlona of the Huttionian Theory of the Earth; by John Playfair. 



