152 
Again, we have not gaged our streams to know the relation between 
the runoff and the rainfall. Such records as are gathered in other com- 
munities will not apply to our peculiar conditions, that is, two water- 
sheds of equal area, one long, narrow and V-shaped, and the other broad 
and flat, will yield very different flows in the streams. Again, the char- 
acter of the surface, whether of rocky formation or swamps or farmland, 
will change the conditions. 
Therefore, to obtain an exact solution of our flood problems we must 
first of all get accurate surveys and determine the flow of our streams. 
This cannot begin too soon. For this reason, the Indiana Flood Commis- 
sion recommends an early beginning of this work of surveys and stream 
gaging. 
These suryeys are most important for another purpose, namely, to 
determine if the water of the upper reaches of the rivers can be held 
back for a time in reservoirs. For instance in the case of the Wabash 
River at Logansport, which carries the floods from the upper Wabash, 
the Mississinewa, the Salamonie, and the Hel River, we would like to 
know if it is possible to find reservoir sites in the valleys of these tribu- 
taries, so that the flood flows may be controlled. Each tributary flood 
might be held back to the proper amount, and for the proper time, so as 
to let these flood flows by Logansport one by one. 
For example, in Ohio, it was found that by reservoir control, flood 
protection could be obtained for the cities of the Great Miami Valley at 
a cost of $17,000,000.00, whereas the total sum of the cost of the indi- 
vidual protection schemes gotten up by each city acting separately was 
over $100,000,000.00. The study of reservoir protection for the Miami 
Valley was made by the use of the topographic maps of the State of Ohio 
from which reservoir sites were planned and preliminary estimates worked 
up. Later on, detailed surveys showed that the preliminary work was 
accurate to within one per cent. The topographic survey of Ohio is 87 
per cent. complete, whereas the Indiana survey is only 9 per cent. com- 
plete. If we were fortunate enough to possess topographic maps of the 
State of Indiana, we could go ahead immediately to study flood protection 
in a more complete Manner. 
The topographic map of the State is not only necessary for complete 
flood protection studies, but it is of use in the following: 
