Mr. McMath. 
432 DISCUSSION: FORESTS, RESERVOIRS, AND STREAM FLOW 
and erosion at other places. The interruptions of silt movement congest 
and obstruct the main line. 
The conclusion is unavoidable, the potential energy of the river 
must be expended in internal work, attrition of moving gravel and 
sand, friction, boils, eddies, etc., in the stream, and in scour of the 
bottom and erosion of banks. 
This view of: river dynamics ‘gives a clue to the difficulties attend- 
ing attempts to improve great rivers by fixation of channel and banks. 
The old tradition of the housewife who fought the North Sea with her 
mop is not far from a parallel case. 
The improvement problem may be fairly stated to be, How to give 
the potential energy, which Man cannot materially increase or diminish, 
something more to do than destructive work. We know that floods 
destroy, but we do not fully know and appreciate the fact that the work 
done at low stages is largely reparative. Reparative work is the re- 
adjusting and removing of high-stage, or flood, deposits so as to restore 
the efficiency of the river bed which is always impaired by flood waves. 
Assuming that such reparation is the fact, the practical solution of 
the improvement problem is to subtract from the flood and add to the 
low-stage energies. This brings reservoirs to the front, for they effect 
this exchange, and nothing else is known that will. The argument 
that they will not prevent all floods is not worthy of attention. The 
question is, how much can they be made to do? 
From 1880 to 1888 the writer was employed by the then newly 
created Mississippi River Commission to make a special study of 
reservoirs, their possibilities, and their relations to river physics. He 
progressed far enough to realize that reservoirs were the natural and 
logical remedy for many physical ills, capable of ameliorating, if not 
curing. 
He became convinced that the dynamic view of river physics, out- 
lined above, was true beyond controversy, and that the first practical 
lesson was the futility of fighting against natural law when it is 
possible to work in harmony with it, by extending and especially by 
perpetuating Nature’s reservoir system. Levees, revetments, and dikes, 
while locally useful and temporarily effective, should have a subordinate 
place. 
It was then argued that concentration of flood waters between levees 
would “lower the Mississippi in its bed” and “set Cairo on a hill.” 
When this idea gained official ascendency, the writer resigned his posi- 
tion and turned to another line of professional work. 
Twenty-five years have passed, levees have been built and main- 
tained along the whole delta course of the river; and millions have 
been spent. Has the river bed been lowered? Has Cairo, relatively 
to high waters, been elevated? Has any stretch of river of considerable 
length yielded to control and been permanently improved? The writer 
appeals to the records. 
